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Flower Bud Induction Overview and Advisory

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS
The following information has been developed as part of the Decision Information System for Citrus

L.  Gene Albrigo, Horticulturist Emeritus
Citrus Research & Education Center, Lake Alfred, FL

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11/1/2004

FLOWER BUD INDUCTION ADVISORY #1 for 2004-2005-11/1/04

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 
The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist Emeritus
Citrus Research & Education Center, Lake Alfred, FL 

Overview of flower bud induction in Florida –  It is time to start following citrus flower bud induction conditions for the coming year's bloom. Low temperatures first stop growth and then promote induction of flower buds as more hours of low temperatures accumulate. A period of 5-12 days of high temperatures in winter can then initiate bud differentiation which after sufficient days of warm springtime temperatures leads to bloom. The meteorologists predict that this winter in Florida will be a weak to moderate El Niño year, cooler and wetter than normal. Even if this winter is only slightly cooler than normal, enough hours of low temperatures below 68 degrees F. should accumulate to induce a moderate to good level of flower buds.

Under normal Florida conditions, sufficient flower bud induction should be achieved when total uninterrupted, accumulated hours of low temperatures exceed 850 hours below 68 degrees F. if the current crop is heavy. If the crop load is light, sufficient flower bud induction can occur after 750 hours of accumulated low temperatures. A warm period of 7 to 12 days, with maximum temperatures > 75 to 80 degrees F., after some low temperatures have accumulated can trigger growth (bud swelling). Fewer days of higher temperatures and lower daytime highs are required to stimulate growth if the accumulated cool temperature hours are high later in the winter. Current and previous seasons weather information is available on the Florida Automated Weather System (fawn.ifas.ufl.edu) for locations near you. The 8 day forecast from the National Weather Service predicts Florida weather for several sites around the citrus belt and is linked to http://www.crec.ifas.ufl.edu/crechome/crecweather.shtml

Some flower buds will be induced in the range of 300 to 600 accumulated hrs < 68 degrees F. Warm events after these levels of induction result in weak flowering intensity, and therefore many buds remain that can be induced by later cool periods. This situation results in multiple blooms. During the years from 1963 to 2002, multiple blooms occurred in over half of the years. Historically, the time period in which a warm 7-12 day period can lead to some bud growth and then result in multiple blooms is roughly Thanksgiving to Christmas. Presently, the only management tool available to eliminate or reduce the chance of multiple blooms is to promote water stress by stopping irrigation before these predicted warm periods occur. If the warm periods(s) are of the typical 7 to 10 day duration, mild water stress will have little impact on current crop development or quality. Mild water stress may be interpreted as leaf wilt observed by 10 or 11 am, but leaves recovering by early the next morning. If no rains interrupt a mild stress condition of citrus trees, buds will not grow in response to high temperatures. If an extended warm period has passed, trees again can be watered to minimize current crop water stress. Although no weather prediction is guaranteed, rains in the winter usually come on the fronts of cool periods. Therefore, the chances of being able to use water stress to prevent an early flower bud differentiation event is reasonably good for most warm periods. A difficulty that occurred 3 years ago, which resulted in a very small crop, was that daytime high temperatures were continuous through the fall until December 18 th . If trees were allowed to be water stressed for this extended a period, this could lead to low photosynthesis, little fruit growth or sugar accumulation and probably excessive fruit drop.

In the shallow soils of bedded groves, it is relatively easy to create sufficient water stress to suppress growth by withholding irrigation for a few days if no rains occur. In deeper sandy soils, 2 or more weeks without irrigation or rainfall may be required. To minimize the time required for soil to dry sufficiently to initiate water stress, the soil should be allowed to dry out by mid-November so that trees show wilt by mid-day. For bedded groves, minimum irrigation can then be applied at low rates as needed until a weather prediction indicates a warm period is expected. At this time, irrigation should be shut down. For deep sands, the soil needs to be dried out and kept nearly dry below 6 to 8 inches of depth until at least Christmas so that no growth can occur. Minimum irrigations that re-wet perhaps the top 6 inches of the root zone may minimize excessive drought, while allowing quick return to a water stress condition if a high temperature period is forecast. This may be risky for ‘Hamlin' or other early maturing cultivars not yet harvested that tend to drop fruit near harvest. Much of what has been stated above has now been incorporated into a ‘Flowering Expert System for Florida Citrus'.

1999-2000_bloom 
(Figure 1, with added information in color or bold lettering, is from the ‘Flowering Expert System for Florida Citrus' and represents the different aspects of apparent flower induction.)

The level of potential flowering would be greater (orange line) with a light crop or less (green line) with a heavy crop for the same amount of hours of induction. Although this representation does not appear on the working screen, recommendations (bottom text box) do consider the current crop level in assessing when action should be taken to try to prevent or to promote initiation of the flower bud growth process. This system will be tested again this winter with several growers that helped us refine the system the past two years. Future advisories (usually weekly) will update accumulating hours of related temperatures and other weather effects on flower bud induction plus methods for enhancing or reducing flowering intensity as conditions and cultivars dictate. Read the archived advisories from previous years (link at top of page) for more background.

Previous 3-year's results – In the winter of 2001-2002 cool temperature accumulation was very slow, warm temperatures persisted and many buds started to grow by 20 December, heavily to vegetative buds. This resulted in few buds remaining for a second flowering wave and a small crop occurred. In the winter of 2003-2003 by late December we had 850 hours of uninterrupted cool inductive temperatures with a low current crop on the trees. The following warm period initiated almost all the buds on all of the spring and summer flush to differentiate and bloom in early March. We had a fairly leafy bloom of very short duration (slightly more than 2 weeks ). In spite of the high temperatures during and following bloom, a good fruit set occurred in other round oranges resulting in the highest October crop forecast for Florida that FASS has ever predicted. Last year (2003-2004), there was good flower bud induction and reasonably good fruit setting conditions, although the heavy previous crop probably reduced flowering levels and set somewhat. Even though fruit size was small, it looked like we were headed for a mid-200 million box orange yield before the hurricanes.

The new season's situation – If you have citrus that was not in the path of the hurricane, two years of heavy to moderately heavy crops means that a high level of induction is desired to produce adequate flower buds for next year's crop. If the block was in the path of one to three hurricanes, then many scenarios exist and most of my conclusions are guess work, but here they are:

If you lost fruit but not many leaves, the trees may need less inductive temperatures, but fruit losses were after most of the summer drain on carbohydrates had occurred. If fall temperatures stay in the mid-70s to low 80s, trees may build up carbohydrate reserves under a low crop situation providing good bud condition for flower induction.

If many leaves were lost along with the crop, then trees may have fairly low carbohydrate levels and need high levels of inductive temperatures to produce a good bloom.

If heavy fruit and leaf loss was followed but many buds stimulated to flush this fall, then fewer buds are available on last year's spring and summer flush for flowering. However, if these fall flushes matures sufficiently before bud growth stimulation occurs (usually in early to late December), then their buds can become flower buds. I think that 2 to 2 ½ months for flush development may be necessary for this to happen.

Therefore, best results this fall-winter may come from reasonable development temperatures until mid-November followed by above average cool temperature accumulation (> 850 hrs).

So far this Fall, little cool weather has occurred to slow down or stop vegetative growth on mature trees, only about 110 to 160 hr < 68 degrees F., from southern to northern districts. Also, the National Weather Service (NOAA) predicts that there will be about 80 more hours below < 68 degrees F. during the next 8 days. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN or for NOAA's 8 day forecast go to Weather Links on our CREC homepage and then 8 day forecast.

The major concerns for the next 60 days are the possibility of 1) continuous warm weather that will push vegetative buds to grow as occurred 3 winters ago or 2) an extended warm period, 10 to 12 days with max. temperatures > 75 to 80 degrees F, following an inductive period of 300 to 500 hrs < 68 degrees F that will initiate differentiation of easily induced flower buds. The first condition will lead to low flowering and the second to multiple blooms. By next week the 200 to 250 total hours will be ½ way to a weak bloom potential. Continued accumulation of cool temperatures or prevention of growth during a winter warm spell are important to a good start to the 2005-06 harvest season. Therefore, keep irrigation amounts low to moderate (if fruit are still present) to minimize growth possibilities. Prepare to keep groves relatively dry, keep track of induction hours in your area and watch for the next advisory.

( Request for potential cooperators) – Although rains this past winter negated attempts to use water stress to delay bloom in many areas and collection of meaningful yields was severely disrupted by the hurricanes, we are still interested in tests to delay bloom by managing irrigation to delay initiation of flower bud growth. This might be accomplished by using water stress to prevent growth during warm winter periods until mid-January has passed. If you are interested in putting a block or a few rows of grapefruit, ‘Hamlin' or ‘Valencia' trees under this protocol, please let me know albrigo@crec.ifas.ufl.edu or phone 863-956-1151).

 


11/08/2004

FLOWER BUD INDUCTION ADVISORY #2 for 2004-2005-11/8/04

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 
The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Please review the background information in the first advisory if you have not already done so.

Current Status: So far this Fall, cool weather has reached 150 to 200 hr < 68 degrees F., from southern to northern citrus districts. Also, the National Weather Service (NOAA) predicts that there will be about 80-90 additional hours below < 68 degrees F. during the next 8 days.

This week's cool weather should bring buds to a rest stage and by the end of next week our major concern will be the possibility of an extended warm period, 10 to 12 days with max. temperatures > 80-85 degrees F, occurring before we have reached an ideal amount of cool temperature flower bud induction. An extended warm spell after an inductive period of 300 to 500 hrs < 68 degrees F will initiate differentiation of easily induced flower buds, and this would lead to an overall weak flowering wave with an early bloom date. Continued accumulation of cool temperatures and prevention of growth initiation during a winter warm spell are important to a good start to the 2005-06 harvest season. Therefore, keep irrigation amounts low to moderate (if fruit are still present) to minimize growth possibilities. Prepare to keep groves relatively dry, keep track of induction hours in your area and watch NOAA's 8-day forecast for possible warm weather that could force initiation of bud growth. Remember this protocol is advised at least until Christmas.

(Request for potential cooperators) – Establishing mild drought stress when warm periods occur through mid-January also might benefit growers by delaying bloom date into mid- to late March as well as compressing the flowering period. Although rains this past winter negated attempts to use water stress to delay bloom in many areas and collection of meaningful yields was severely disrupted by the hurricanes, we are still interested in tests to delay bloom by managing irrigation to delay initiation of flower bud growth. I have received one new positive response to putting some blocks into this protocol. If you are interested in putting one or more blocks or a few rows of grapefruit, ‘Hamlin' or ‘Valencia' trees under this protocol, please let me know albrigo@crec.ifas.ufl.edu or phone 863-956-1151).

.


11/15/2004

FLOWER BUD INDUCTION ADVISORY #3 for 2004-2005-11/15/04

Current Status: As predicted last week, accumulated cool weather has now reached 200 to 300 hr < 68 degrees F. from southern to northern citrus districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be about 80-90 additional hours below < 68 degrees F. during the next 7 days. This means that all areas will be in the low flowering potential level by next week. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN or for NOAA's 8 day forecast go to Weather Links on our CREC homepage and then 8 day forecast.

Up to this week, cool temperature accumulation has been about average compared to the last 4 years. The predicted rate of accumulation for the next 8 days is also average, but an extended warm period the last week of November or in early December would lead to an overall weak flowering wave which would have an early bloom date. Continued accumulation of cool temperatures and prevention of growth initiation during a winter warm period are important to a good start to the 2005-06 harvest season. Therefore, keep irrigation amounts low to moderate (if fruit are still present) to minimize growth potential during a warm period. Prepare to keep groves relatively dry, keep track of induction hours in your area and watch NOAA's 8-day forecast for possible warm weather that could force initiation of bud growth. Remember this protocol is advised at least until Christmas.

Please email or phone me if you have any questions (albrigo@crec.ifas.ufl.edu or phone 863-956-1151).


11/22/2004

FLOWER BUD INDUCTION ADVISORY #4 for 2004-2005-11/22/04

Current Status:  Accumulated cool weather has now reached 270 to 400 hr < 68 degrees F. from southern to northern citrus districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be about 80-90 additional hours below < 68 degrees F. during the next 7 days. This means that all areas will be in the low to moderate range of flowering potential by next week. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN or for NOAA's 8 day forecast go to Weather Links on our CREC homepage and then 8 day forecast. The weather records for Lake Alfred are somewhat out of line with other areas, warmer, and need to be evaluated further to see if this central area is warmer or the weather records are incorrect.

Up to this week, cool temperature accumulation has been about average compared to the last 4 years. The predicted rate of accumulation for the next 8 days is also average, but an extended warm period in early December would lead to an overall weak flowering wave, which would have an early bloom date. The NOAA 8 day forecast is predicting slightly cooler weather the end of this week. Hopefully, this trend will continue into mid- to late December, but a warm period often occurs up in December.

Continued accumulation of cool temperatures and prevention of growth initiation during a winter warm period are important to a good start to the 2005-06 harvest season. Therefore, keep irrigation amounts low to moderate (if fruit are still present) to minimize growth potential during a warm period. Low to deficit irrigation is recommended now to prepare groves so that drought stress can be imposed quickly if a warm period is predicted. Since temperatures have been fairly high, it would be a good idea to hold off on further irrigation until the cool period starts later this week. Keep track of induction hours in your area and watch NOAA's 8-day forecast for possible warm weather that could force initiation of bud growth. Remember this irrigation protocol is advised until Christmas. We need at least another 4 weeks of cool

Please email or phone me if you have any questions albrigo@crec.ifas.ufl.edu or phone 863-956-1151)


11/29/2004

FLOWER BUD INDUCTION ADVISORY #5 for 2004-2005-11/29/04

Accumulated cool weather has now reached 320 to 465 hr < 68 degrees F. from southern to northern citrus districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be about 60-80 additional hours below < 68 degrees F. during the next 7 days. This means that all areas will still be in the low to moderate range of flowering potential through this week, but the accumulated hours will be past the midway point in that category for all citrus areas and some northern areas should be near the break point of 600 hours. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN or for NOAA's 8 day forecast go to Weather Links on our CREC homepage and then 8 day forecast. The cool weather accumulation for Lake Alfred is still below that of Immokalee.

Up to now, cool temperature accumulation has been about average compared to the last 4 years. It is lower than in 2002 but higher than last year. The predicted rate of accumulation for the next 8 days is lower than it has been the previous 2 weeks. Many areas had enough rain over the long weekend to provide adequate soil moisture for bud growth if an extended warm period occurs in early December. Hopefully, the root zone will dry down enough by next week to prevent growth if temperatures warm up by then. The NOAA 8 day forecast is predicting slightly cooler weather the end of this week. Hopefully, this trend will continue into mid- to late December, but remember that a warm period often occurs in December.

Continued accumulation of cool temperatures and prevention of growth initiation during a winter warm period are important to a good start to the 2005-06 harvest season. Therefore, keep irrigation amounts low to moderate (if fruit are still present) to minimize growth potential during a warm period. Low to deficit irrigation is recommended now to prepare groves so that drought stress can be imposed quickly if a warm period is predicted. Since temperatures have been fairly high and some rainfall occurred this past weekend in many areas, it would be a good idea to hold off on further irrigation this week and wait to see what next week will bring. Keep track of induction hours in your area and watch NOAA's 8-day forecast for possible warm weather that could force initiation of bud growth. Remember this irrigation protocol is advised until Christmas. We need at least another 3 to 4 weeks of cool weather to be in a good position regarding flower bud induction (+ 800 hours). Try not to let a warm period break the process.

For trees not affected by the hurricanes and producing a good crop for the second year in a row, it may take near 900 hours < 68 degrees F. to provide adequate flower bud induction. Since temperature highs on most days the past two months have been near 80 degrees F. or higher, trees with fall flush due to leaf loss from one or more hurricanes have had time to mature much of the fall flush. This means that these trees should have adequate flower buds if the cool weather continues. It is particularly important for these trees that cool temperature accumulation continues to a high level (approaching 900 hours < 68 degrees F.). Therefore, this winter in Florida all trees would do better if higher levels of flower bud induction occurred than are normally required.

Please email or phone me if you have any questions albrigo@crec.ifas.ufl.edu or phone 863-836-1151.


12/6/2004

FLOWER BUD INDUCTION ADVISORY #6 for 2004-2005-12/6/04

Current Status:  Accumulated cool weather has now reached 400 to nearly 600 hr < 68 degrees F. from southern to northern citrus districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be about 80-83 additional hours below < 68 degrees F. during the next 7 days. This means that all areas will be in the upper part of the low to moderate range of flowering potential by next week, and the cooler districts should reach the first stage of the moderate to high range, exceeding 600 hours. The NOAA forecast for the coming week is a continued increase in cool hours with the first 3 to 4 days having daytime highs in the lower 80s, followed by 3 days with highs in the lower 70s. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN, or for NOAA's 8 day forecast go to Weather Links on our CREC homepage and then 8 day forecast.

Up to now, cool temperature accumulation is still about average compared to the last 4 years. It is lower than in 2002 but higher than last year. The predicted rate of accumulation for the next 8 days is higher than it has been the previous 2 weeks. Rain is predicted towards the end of this week, followed by cooler weather. Don't irrigate this week until you see how much rain you get and if the cool period materializes. We need the NOAA predicted cooler weather the end of this week to continue into mid- to late December. Remember that a warm period often occurs in December and the terminal buds on spring and summer shoots are now easily stimulated to initiate growth by a warm period (probably 5 to 7 days in the mid-80s) if soil moisture is adequate for flower buds to initiate growth.

Continued accumulation of cool temperatures and prevention of growth initiation during a winter warm period are important, therefore, keep irrigation amounts low to moderate (if fruit are still present) to minimize growth potential during a warm period. Soil moisture below 50 to 60 % depletion is probably necessary to prevent bud growth. Low to deficit irrigation is recommended now to keep groves near drought stress if a warm period is predicted. Since temperatures have been fairly high and some rainfall occurred this past week in many areas, it would be a good idea to hold off on further irrigation this week and wait to see what the end of the week will bring. Keep track of induction hours in your area and watch NOAA's 8-day forecast for possible warm weather that could force initiation of bud growth. Check the NOAA forecast at least every other day so that you don't get surprised by a warm period. Remember this irrigation protocol is advised until Christmas. We need at least another 3 to 4 weeks of cool weather to be in a good position regarding flower bud induction (+ 800 hours). Try not to let a warm period break the process.

For trees not affected by the hurricanes and producing a good crop for the second year in a row, it may take near 900 hours < 68 degrees F. to provide adequate flower bud induction. Since temperature highs on most days the past two months have been near 80 degrees F. or higher, trees with fall flush due to leaf loss from one or more hurricanes have had time to mature much of the fall flush, perhaps excepting flush after Hurricane Jeanne. This means that these trees should have adequate flower buds if the cool weather continues. It is particularly important for these trees that cool temperature accumulation continues to a high level (also approaching 900 hours < 68 degrees F.). Therefore, this winter in Florida all trees would do better if higher levels of flower bud induction occurred than are normally required.

It is time to start thinking about flower induction enhancing sprays (urea or phosphorous acid (PO3)). They will be most useful if a warm period is predicted from near to shortly after Christmas and the total hours < 68 degrees F. has not reach 850 hours. Trees with severe defoliation from hurricanes this summer may not be good candidates for these sprays this winter since there will not be as much surface area available to catch the spray. If direct contact with the buds is sufficient, it will not matter if few leaves are present. Unfortunately I don't know the answer to the question, ‘Which tissue needs to be present to absorb the spray material?' (another hurricane puzzle). Anyway, if you are anticipating spraying one of these products, be sure you have material on hand. For urea, you need 53 to 60 lbs of urea available per acre you plan to treat. For a PO3 product you need 3 pints to 2 quarts per acre depending on which product you use (60 % P (3pts) or if 26 % P (2 qts) product)

Next weeks advisory may not be out until late Monday or Tuesday morning. Please email or phone me if you have any questions (albrigo@crec.ifas.ufl.edu or phone 863-956-1151)


12/13/2004

FLOWER BUD INDUCTION ADVISORY #7 for 2004-2005-12/13/04

Accumulated cool weather has now reached 470 to nearly 700 hr < 68 degrees F. from southern to northern citrus districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be about 120 to 168 additional hours below < 68 degrees F. during the next 7 days. This means that all areas will be in the moderate to high range of flowering potential by next week, and the cooler districts should reach the mid-point of this range. The NOAA forecast for the coming week is generally for all temperatures to be in the inductive range, although some northern areas will have a few hours below the effective range (<40 degrees F.) and the Gulf region may have a few hours above the effective 68 degrees F. A freeze is not predicted, but citrus areas from Central to Northern Districts may have temperatures near 32 degrees F. Wednesday morning according to NOAA. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN, or for NOAA's 8 day forecast go to Weather Links on our CREC homepage and then 8 day forecast.

Up to now, cool temperature accumulation has been about average compared to the last 4 years. The predicted rate of accumulation for the next 7 days is higher than normal for this time of year. Most areas received some rainfall this past week, but if not, light irrigation this week is safe as buds will be held in check by the cool weather. If this week's predicted weather continues for the following week, central to northern areas will be near 900 hours < 68 degrees F. Southern areas will need another week after that to reach that goal. If a warm period occurs before then and soil moisture is adequate, the terminal buds on spring and summer shoots are now easily stimulated to initiate growth. As of today, the model does not indicate that a wave of buds has started to initiate growth after the warm days that just ended. The Immokalee area had a 6-day period with daily highs from 82-85 in November and 5 days of 81 to 85 in December, but these periods were separated by a cooler period. Other areas had cooler daytime highs.

Low to deficit irrigation is still recommended now to keep groves near drought stress if a warm period does occur before three more weeks of cool temperature accumulation. Keep track of induction hours in your area and watch NOAA's 8-day forecast for possible warm weather that could force initiation of bud growth. Check the NOAA forecast at least every other day so that you don't get surprised by a warm period. Remember this irrigation protocol is advised until Christmas. We need at least another 2 to 3 weeks of cool weather to be in a very good position regarding flower bud induction (+ 900 hours). Try not to let a warm period break the process.

See last week's advisory about hurricane affected trees and their flowering potential. Also look at last week's advisory about planning for urea or PO3 sprays to enhance flowering. If the cool weather continues until we reach 900 hours < 68 degrees F., the need for using one of these sprays will be greatly diminished. Weak blocks might be more likely to respond. If a warm period occurs in the next 2 (northern) or 3 (southern areas) weeks, then it is the time to spray. This provides a window of about 7 days to cover the areas you decide on before bud development has advanced too far.

Please email or phone me if you have any questions albrigo@crec.ifas.ufl.edu or phone 863-956-1151.


12/20/2004

FLOWER BUD INDUCTION ADVISORY #8 for 2004-2005-12/20/04

Accumulated cool weather has now reached 620 to 850 hr < 68 degrees F. from Southern to Northern Citrus Districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be about 110 to 140 additional hours below < 68 degrees F. during the next 7 days. This means that all areas will be above the mid-point of the moderate to high range of flowering potential by next week, and the northern areas will reach the high range. The NOAA forecast for the coming week again is generally for all temperatures to be in the inductive range, although two cold fronts (Tuesday and Saturday) may produce a few hours below the effective range (<40 degrees F.). The coldest front is expected to be at or near freezing in Central to Northern Districts. Go to http://www.wunderground.com/US/Region/US/JetStream.shtml and follow the jet-stream pattern tonight. If we maintain lateral flow off the Gulf, we should avoid a hard freeze. If the north to south jet-stream flow becomes stronger than the lateral flow, watch out. As of 6 am Monday, the flow pattern looked favorable. Check it again this evening. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN, or for NOAA's 8 day forecast go to Weather Links on our CREC homepage and then 8 day forecast.

Trees are now making very good progress towards accumulating sufficient cool temperature induction. The predicted rate of accumulation for the next 7 days is higher than normal for this time of year. If this week's predicted weather continues for the following week, central to northern areas will be above 900 hours < 68 degrees F. Southern areas will reach the 900 hour goal with another week of cool weather between Christmas and New Year. If a warm period occurs that week and soil moisture is adequate, the terminal buds on spring and summer shoots will be easily stimulated to initiate growth. The model still does not indicate that a wave of buds has started to initiate growth after the warm days in early December. We are on track to have a single intense bloom in most areas and likely in all areas if the weather stays cool through New Year's day.

A warm period in late December or early January will initiate bud growth for a bloom in early March. Several growers will be trying to delay that growth by maintaining low to deficit irrigation through any warm periods until late January. This should result in a late March bloom date. Keeping groves near drought stress will prevent bud growth if a warm period does occur before then.

Keep track of induction hours in your area and watch NOAA's 8-day forecast for possible freezes or warm weather that could force initiation of bud growth. Check the NOAA forecast at least every other day for development of either condition.

See earlier advisories about hurricane affected trees and their flowering potential (return bloom now looks promising). Also look at earlier advisories about planning for urea or PO3 sprays to enhance flowering. The need for using one of these sprays is greatly diminished. Weak blocks might be more likely to respond, particularly in southern areas. If used, these sprays should be applied as the weather warms up at the first warm period, and you can have effective results until 3 or 4 days into the warm period. Usually, this provides a 7 day spray window for these applications. If cool temperatures last through the first week of January, it is not likely that these sprays will be beneficial since a very good level of natural flower bud induction will have been reached..

I plan to post a short advisory next Monday. Please email or phone me if you have any questions albrigo@crec.ifas.ufl.edu or phone 863-956-1151).


12/27/2004

FLOWER BUD INDUCTION ADVISORY #9 for 2004-2005-12/27/04

Please review the background information in the first advisory if you have not already done so.

Accumulated cool weather has now reached 733 to 1015 hr < 68 degrees F. from Southern to Northern Citrus Districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be an additional 83-100 hours below < 68 degrees F. during the next 7 days. This means that all areas, except the Indian River District, will be in the high range of flowering potential by next week. The NOAA forecast for the coming week is generally for daytime temperatures to be in the upper 70s by Thursday or Friday. To view specific FAWN data for a location near you in the citrus growing areas, use ( www.crec.ifas.ufl.edu ) and click on FAWN, or for NOAA's 8-day forecast go to Weather Links on our CREC homepage and then the 8-day forecast.

It now appears that all districts will accumulate at least 900 hours < 68 degrees F. before a sufficient warm period occurs to initiate flower bud growth. This should be a good level for flowering under our current situation. Look at previous advisories for discussion of tree conditions this year. All areas received some rainfall over the Christmas weekend with Central to Northern Districts getting 1 to 2 inches. According to the FAWN system, most Southern areas received .5 to 1 inch. In general, soil moisture currently is sufficient for bud growth. If the predicted warming trend the end of this week occurs and continues into next week, bud growth will likely be initiated sometime next week. Blocks that received no more than .5 inches of rain may dry out enough to be in enough drought stress next week to avoid initiation of bud growth. If the weather stays cool enough into next week, all areas may avoid initiation of bud growth next week. At the current high level of induction, five or six days near 80 degrees should initiate flower bud growth. If the warming trend does persist, only areas with low rainfall this past weekend are good candidates for delayed bloom by continuing to withhold irrigation.

For blocks that you wish to supplement bud induction with a urea or PO3 spray, the projected warmer weather may be the time to apply these sprays. Temperature for good spray uptake should be in the 70s. Unfortunately, these temperatures are projected for Thursday or Friday (Could ruin your New Year's weekend if you need to spray large acreages). If by Thursday, the 8-day forecast or your local weather news (5 or 6 day forecast) projects temperatures continuing above 75 degrees each day, then initiation of bud growth is likely. All sprays should then have been applied by the middle of next week.

The Citrus Research and Education Center will be closed this week. If you have any questions about spraying or if a block may dry out enough to avoid bud growth initiation next week, you can email me this week albrigo@crec.ifas.ufl.edu


1/3/2005

FLOWER BUD INDUCTION ADVISORY #10 for 2004-2005-1/3/05

It has happened! The flowering model indicates that initiation of flower bud differentiation has started in most areas, probably all. Accumulated induction hours were at 820 to 830 hours < 68 degrees F. from South to North when the process started on December 22 or 23 (about 9 days ago).

Two areas, Ft. Pierce and Lake Alfred don't show initiation to have started, but this may be due to incorrectly monitored low induction hours indicated by FAWN, particularly for Lake Alfred. These two areas currently have 840 and 973 hr < 68 degrees F., respectively. Accumulated cool weather to date has reached 840 to 1150 hr < 68 degrees F. from Southern to Northern Citrus Districts, respectively. Also, the National Weather Service (NOAA) predicts that there will be an additional 80 hours below < 68 degrees F. during the next 7 days. These hours may affect some additional buds during the transition period or add to the potential for a second wave of flowering. However the prolonged warm period is still on us and is likely to push most buds into flowering or vegetative shoot growth. The NOAA forecast for the coming week is for daytime temperatures to be in the upper 70s to low 80s. To view specific FAWN data for a location near you, use ( www.crec.ifas.ufl.edu ) and click on FAWN, or for NOAA's 8-day forecast go to Weather Links on our CREC homepage and then the 8-day forecast.

I was hoping we would reach 900 hrs < 68 degrees F. before the initiation of flower bud growth, but many areas did not achieve this. Most Central to Northern Districts received 1 to 2 inches of rainfall over the Christmas weekend, while most Southern areas received < .5 to 1 inch. Soil moisture is sufficient for bud growth in most citrus areas so the indicated initiation has occurred where the root zone is wet. For Central to Southern areas, blocks that had or still have a good current crop may benefit from a urea or PO3 spray to enhance bud induction. Three to 4 days remain in which these sprays may be effective. Daytime temperatures, in the 70s, will be good for spray uptake.

Blocks that received less than .5 inches of rain may be dry enough now to have drought stress, which will prevent the current initiation of bud growth. These potential blocks for delayed bloom can be evaluated by looking for leaf wilting by 11 am to noon. With the continuing warming trend, only areas with low rainfall over Christmas are good candidates for delayed bloom by continuing to withhold irrigation. Examine the first two buds from the apex of summer shoots by hand lens to see if they are swollen compared to buds 6 or 7 leaves down. If no buds are swollen, initiation has not started and drought stress will continue to prevent it.

If you have any questions about spraying or if a block is dried out enough to avoid bud growth initiation, you can contact me by phone (863-956-1151) or email (albrigo@crec.ifas.ufl.edu ).


1/10/2005

FLOWER BUD INDUCTION ADVISORY #11 for 2004-2005-1/10/05

Its still happening! The flowering model indicates that initiation of flower bud differentiation has started in all areas. Accumulated induction hours were at 830 to 1130 hours < 68 degrees F. from South to North when the process started on December 30 th (Ft. Pierce, December 22 nd or 23 rd in southwestern areas, December 25 th in central areas and December 30 th in northern areas. Swell of shoot apex buds has been confirmed in Ft. Pierce and Lake Alfred.

Two locations for which the model did not show initiation of differentiation last week, Ft. Pierce and Tavares, were probably behind because of lower induction hours at Ft. Pierce and lower daytime temperatures at Tavares. Lake Alfred might have been delayed due to both conditions. Bud swell was not detected in Lake Alfred until the middle of last week, somewhat confirming the model results. Since the start of flower bud differentiation, another 100 to 250 hours of induction conditions have accumulated. The program further predicts, using National Weather Service (NOAA) data, that there will be an additional 60 to 120 hours below < 68 degrees F. during the next 7 days. These hours may cause enough additional buds to be induced to flower for a second wave of flowering. However, the level of induction for the first wave of buds was fairly high (839-1100), and I expect most available buds to be in the first wave of flowering. To view specific weather data for a location near you, use ( www.crec.ifas.ufl.edu ) and click on FAWN, or for NOAA's 8-day forecast go to Weather Links on our CREC homepage and then the 8-day forecast. Additional weather data links are also listed.

From available rainfall data, it appears that only the area around Clewiston, LaBelle and Immokalee had low enough rainfall (< .5 inches) during the Christmas weekend for trees to have been in drought stress, and therefore for initiation of flower buds not to have started during the prolonged warm period that is currently visiting us. Any trees in that general area that were well irrigated did start the initiation of flowering. Examine the first two buds from the apex of summer shoots by hand lens to see if they are swollen compared to buds 6 or 7 leaves down. If no buds are swollen, initiation has not started and drought stress will continue to prevent it until the trees are irrigated or a rain rewets the soil. These blocks for potential delay of bloom should be showing leaf wilting by 11 am to noon. The NOAA forecast for the coming week has daytime temperatures still in the upper 70s to low 80s through Friday and then a cool front with potential for rain will drop daytime highs into the 60s (northern half of citrus areas) to low 70s (southern half). The cooler weather may last for at least the following week.

With the long warming trend, only trees in areas with low rainfall over Christmas are good candidates for delayed bloom by continuing to withhold irrigation. If sufficient rain occurs this coming weekend in the southern area, flower bud differentiation may start when temperatures again are in the mid to high 70s. If the cool period next week is mostly below 70 degrees F and long enough for soil moisture to again be depleted, then bud growth may again be prevented during the next warm period. In order to produce later maturing, higher solids fruit as a response to later flowering, I think it will be desirable for the flower bud growth process not to start until after January 20th.

Currently general bloom dates are projected from late February through March 4 th . In some cases this is one to two days earlier than projected one week ago. The continued warm weather this week may further shorten the time to the estimated bloom date.

Many people are reporting very hard looking trees in the hurricane path, particularly the fall flush stimulated by leaf loss. Flowering on this flush may be reduced because of low carbohydrate and nutrient levels. Fruit set may also be impacted. It will be very important to start this year's nutritional program on these impacted trees early in order to have good nutritional levels in the tree at least 2 weeks before the projected late February, early March bloom date.

While nutritional programs are becoming very important for next years crop, I think it is now too late to get any benefit by enhanced flowering from foliar sprays of urea or PO3.

If you have any questions about bud growth initiation and flowering, you can contact me by phone (863-836-1151) or email (albrigo@crec.ifas.ufl.edu ).


1/17/2005

FLOWER BUD INDUCTION ADVISORY #12 for 2004-2005-1/17/05

Some interesting things are happening according to the flowering monitoring system! The model indicates that initiation of flower bud differentiation has started for 2 waves of flowering in lower central areas from Sebring through Ona, but not in the Ft. Pierce or Immokalee areas nor from Lake Alfred north. The second wave of flowering for the central areas is based on accumulated induction hours of only about 200 additional hours since the first wave started. This appears to be a small change that should not result in a significant second wave of flowers. Further, the bloom date difference is only 2 weeks, which will not be noticeable. The total accumulated hours < 68 degrees F were at 989 to 1376 hours < 68 degrees F. from South to North as of today. Considering that this week will be very cool an additional 300 to 400 hours will have accumulated by next Monday since the first wave of flower bud differentiation started. These hours will contribute to a second flowering wave for the southern and northern areas. Because of either heavy crops or hurricane leaf loss induced fall flush, trees are likely to respond with a second flowering wave when temperatures warm up after this cool period.

To view specific weather data for a location near you, use ( www.crec.ifas.ufl.edu ) and click on FAWN, or for NOAA's 8-day forecast go to Weather Links on our CREC homepage and then the 8-day forecast. Additional weather data links are also listed.

From available rainfall data, it appears that only the area around Clewiston, LaBelle and Immokalee had low enough rainfall (< .5 inches) this past weekend for trees to have remained in drought stress, and therefore for initiation of flower buds not to have started during the prolonged warm period that occurred until this weekend. Any trees in that general area that were well irrigated did start the initiation of flowering and are projected to be in full bloom on February 28 th . For those in this southern area that have been maintaining drought stress by withholding irrigation, trees should start to receive water when the weather warms up after this cool period. Trees will then probably bloom in late March rather than late February. To be sure that trees have not started initiation of flower bud differentiation, check apex lateral buds for swelling compared to basal buds on summer shoots.

Currently general bloom dates are still projected from late February through March 4 th . The second wave of flowering projected by the flowering monitoring system should be at full bloom on March 14th.

Heavy crops the last two years and hurricane induced leaf loss have left many trees low in carbohydrates and nutrients. Soil applied nutritional programs should be started by early February to have nutrients in the tree at least 2 weeks before the projected early March bloom date. While good nutritional programs are especially important for next years crop, I think it is now too late to get any benefit of enhanced flowering in the first initiation wave of flower buds from foliar sprays of urea or PO3. The projected second wave of flowering in southern citrus production areas could be enhanced by a foliar spray of urea or PO 3 applied at the end of this current cool period. This is a hard decision to make as there may be enough flowers in the first wave for an economic crop. For anyone choosing to do either of these sprays, the timing rules discussed in previous advisories apply regarding early in the next warming period. At the same time, navel blocks may have too many flowers if this second flowering wave occurs. A spray of 10 ppm GA 3 applied at the beginning or up to 5 days into the next warming period can diminish the flowering level (see EDIS report HS-799, listed and quick-linked at the top of this page).

If you have any questions about bud growth initiation and flowering, you can contact me by phone (863-836-1151) or email albrigo@crec.ifas.ufl.edu .

 


1/24/2005

FLOWER BUD INDUCTION ADVISORY #13 for 2004-2005-1/24/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 
The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

All citrus areas now appear to have a second wave of flowering based on the ‘Citrus Flowering Monitoring System'. However by District, the second wave is presumably occurring after only an additional 120 to 230 hours of accumulated hours < 68 degrees F., and the bloom date difference between the first and second wave is only 2 weeks, which will not be noticeable. As of today the total accumulated hours < 68 degrees F are now from 1140 to 1530 hours from South to North. Also the cool temperatures this week will add an additional 80-100 hours resulting in a total of 400 to 500 induction hours since the first wave of buds started differentiation.

When warmer temperatures occur from Wednesday to Thursday this week, this could start another wave of flower bud differentiation. Because of either heavy crops or late fall flush induced by leaf loss during the hurricanes, trees may respond with another flowering wave that would bloom in late March or early April. The buds on the late fall flush needed at least 2 months of warm weather to mature so that the buds could respond to the induction temperatures. Some of the later fall flush may not have had time to accomplish that by the late December warm period.

Buds that would start to differentiate later this week would result in a late March bloom. These and buds that are already growing should have good tree water conditions from now through fruit set. Irrigation should commence as this warm period begins Wednesday or Thursday. Ideally fertilization should occur soon also, at least by early February, so that new nutrients are in the tree 2 weeks before the anticipated late February bloom.

Currently general bloom dates are still projected from February 26 th through March 12 th for the first wave of flowering from Southern to Northern locations. A second wave of flowering is projected to occur from March 16 th to March 20 th by the flowering monitoring system. There should be no additional flowering after the possible third wave mentioned earlier and projected for late March.

To view specific weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage ( www.crec.ifas.ufl.edu ). Additional weather data links are also listed.

If you have any questions about bud growth initiation and flowering, you can contact me by phone (863-836-1151) or email (albrigo@crec.ifas.ufl.edu ).


1/31/2005

FLOWER BUD INDUCTION ADVISORY #14 for 2004-2005-1/31/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Please review the background information in the first advisory if you have not already done so.

Will we have a third wave of flowering? A warm period started the 25 th to 26 th of January and by its end should be enough warm weather to initiate a third flowering wave if induced flower buds are still available. I think there is some possibility of this, particularly for hurricane affected trees that had a heavy fall flush. Generally, the initiation of differentiation of this wave of flower buds would come after flower bud induction from 1250 to 1450 hours of accumulated hours < 68 degrees F.. The bloom date would be around the first of April. By next week, the ‘Citrus Flowering Monitor System' should indicate if it detects the proper conditions for a third wave of initiated flower buds and the projected full bloom date.

All of you that have been looking are seeing the feather push of the new growth in the first 3 to 4 buds from the apex on summer and spring shoots. Flowers are evident, but it is too early to decide if there are enough. I have seen one example of 6 flowers with leaves. Hopefully, most buds will have 2 or 3 flowers with some associated leaves. Currently general bloom dates are still projected from February 26 th through March 12 th for the first wave of flowering from Southern to Northern locations. The second wave of flowering is projected to occur from March 14 th to the 20 th by the Citrus Flowering Monitor system. There should be no additional flowering after the possible third wave mentioned earlier and projected for late March to early April

To view specific weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage ( www.crec.ifas.ufl.edu ). Additional weather data links are also listed.

If you have any questions about bud growth initiation and flowering, you can contact me by phone (863-956-1151) or email albrigo@crec.ifas.ufl.edu .

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2/7/2005

FLOWER BUD INDUCTION ADVISORY #15 for 2004-2005-2/7/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Please review the background information in the first advisory if you have not already done so.

The ‘Citrus Flowering Monitor' system does not indicate that there will be a third wave of flowering, but only two. The two initiation of differentiation periods came after 830-1100 and 940-1250 accumulated hours < 68 degrees F. from southern to northern citrus areas. The corresponding projected bloom dates are 2/25 to 3/14 and 3/15 to 3/22, respectively for the first and second full bloom dates of each wave.

This is the first time in the past 3-4 years that there has been a 2-week spread in projected bloom dates from southern to northern citrus areas. Since the two waves are predicted to be about 18 days apart, the bloom period will appear to be prolonged and not discrete blooms.

Because of the unusual conditions this year leading to a strong fall flush, I am not at all certain that the ‘Citrus Flowering Monitor' will accurately project the behavior of flushes during that period. The difference in flowering dates predicted by the program for the various citrus districts is also something new to watch.

Since the buds are pushing and the bloom dates are soon, we will not have long to wait before seeing the accuracy of the predicted bloom behavior. There is still a good possibility that fall flush after Jeanne may respond late or not at all. Trees in the Immokalee area that were kept dry from Christmas through early January are also likely to bloom later. The ‘Citrus Flowering Monitor' was not programmed for either of these circumstances.

To view specific weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage ( www.crec.ifas.ufl.edu ). Additional weather data links are also listed.

While I am traveling on another project, the flowering advisories may be off schedule for the next two weeks. I should have email and still get out some kind of a report about weekly. If you have any questions about bud growth initiation and flowering, you can contact me by email only(albrigo@crec.ifas.ufl.edu ).

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2/14/2005

FLOWER BUD INDUCTION ADVISORY #16 for 2004-2005-2/14/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

There has been little change in the predicted bloom dates for citrus trees in the various production areas of Florida. Southern areas should still have full bloom in late February and central areas in early March. Northern areas are now projected to be a little later March 15 th ). The second wave of flowers will be out in mid March in all areas except the north, where the second wave of flowers is expected about March 23rd.

I am away for two weeks, and I don't have a report of the condition of buds on the late fall flushes that occurred after the hurricanes. I should be able to summarize observations on these late flushes in two weeks after I return.

While visiting our citrus producing neighbors to the south, I am observing that they have had their flowering problems this year also. The southern production areas of Brazil's Sao Paulo State had rains with cool temperatures last winter and a good, normal bloom. The northern areas were wet but warm and did not get any flowering at the beginning of the spring period. Flowering did not occur until after the rains stopped, 2 months of drought occurred and then rains started tree growth. This will lead to two different harvesting periods for northern and southern citrus production areas. Most of the healthy trees in the north now have a good crop..


2/21/2005

FLOWER BUD INDUCTION ADVISORY #17 for 2004-2005-2/21/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Predicted bloom dates for citrus trees in the various production areas of Florida are perhaps a day or two earlier than previously expected. For processing oranges, southern areas should have full bloom from 24 to 26 February and central areas about 4 March. Northern areas are projected to be a little later March 15 th . The second wave of flowers will be out in mid March in all areas except the north, where the second wave of flowers is expected about March 23 rd . Navels oranges should be in full bloom about 6 to 7 days earlier and small flowered mandarins about 6 days later than most round orange cultivars.

Please report any confirmations or differences of these bloom dates in your area. For locations in the southern areas where maintenance of drought stress may have been successful, please note if the early bloom date was avoided or diminished and when the major bloom occurred. Send any information or questions to albrigo@crec.ifas.ufl.edu


2/28/2005

FLOWER BUD INDUCTION ADVISORY #18 for 2004-2005-2/28/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Please review the background information in the first advisory if you have not already done so

Observations and reports from several people in the industry indicate that the first wave of flowers is occurring about on schedule, perhaps 3 or 4 days later than predicted by the ‘Citrus Flowering Monitor' system (see earlier advisories for dates in your area). However, the amount of flowers in the first wave is highly variable. Very weak, diseased, trees have a good bloom and ahead of predicted bloom dates (February 25-March 5 th ). Some blocks have a good first wave of flowers, but often flowers with few leaves, while other trees are showing almost no flowers. These differences may often relate to the crop load the past two years. Heavy cropping trees may have very low flower counts in this first wave.

Most trees have a second wave of buds pushing out that are maybe 3 to 5 mm in length. Flowering in this wave is not known at this point. Buds on fall flush are out enough to see some flowers if the flush occurred just after the first two hurricanes. Late fall flush after Hurricane Jeanne is just now pushing in the River District and flowering is not determined. By next week, the amount of flowering should be clearer. It does not look like flowering levels will be very high in some blocks unless the second wave is much better than the first. In some cases this may be due to two heavy crops and in others, the hurricanes and leaf loss also may be involved.

Flowering of trees with continuous winter drought in the southern area around LaBelle and Immokalee appear to be significantly behind for time of flowering compared to well irrigated blocks. These growers are reporting a projected bloom date after March 15 th and apparently one wave of flowers. The level of flowering and full bloom date still need to be assessed.

To view specific spring weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage www.crec.ifas.ufl.edu . Additional weather data links are also listed.

If you have any questions about bud growth initiation and flowering, you can contact me by email (albrigo@crec.ifas.ufl.edu ) or call 863-956-1151.


3/7/2005

FLOWER BUD INDUCTION ADVISORY #19 for 2004-2005-3/7/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Please review the background information in the first advisory if you have not already done so.

The first wave of flowers has occurred about on schedule as predicted by the ‘Citrus Flowering Monitor' system (see earlier advisories for dates in your area). The full bloom date might be 3 or 4 days later than predicted. This has occurred the last 3 years.

After traveling to several groves this past week, it is even more obvious that the amount of flowers in the first wave is highly variable. Very weak, diseased, trees have a good bloom that opened ahead of predicted bloom dates (February 25-March 5 th ). Some other blocks have a good first wave of flowers, but often flowers with few leaves, while other trees or whole blocks of trees are showing almost no open or popcorn stage flowers.

Most trees have a second wave of buds pushing out that may now be an inch or more in length. In most groves and blocks visited, there are a number of flowers in this wave. This wave should be in full bloom about mid-March. Buds on fall flush are out enough to see flowering when the flush occurred just after the first two hurricanes. Late fall flush after Hurricane Jeanne is now pushing in the River District and some flowering is reported on this flush as well. Trees that had heavy leaf loss are flushing from adventitious buds on older wood (2 or 3 year old and up to thumb diameter). Flowers are present in some of this flush. Flowering in hurricane affected, structurally sound grapefruit trees looks good. It remains to be seen if these flowers will set well on trees without a full canopy of mature leaves.

Heavy cropping and hurricane leaf loss may be responsible for very low flower counts with few leaves in the first wave and heavier flowering in the second wave. The 3 to 4 day delay in full bloom compared to the model this year and the previous 2 years also may be due to heavy crop loads, which are known to delay bloom. Adjustments for crop load effects on intensity and date of flowering are now planned for the ‘Citrus Flowering Monitor' system.

Flowering of trees with continuous winter drought in the southern area around LaBelle and Immokalee appear to be significantly behind for time of flowering compared to well irrigated citrus. A projected bloom date is late in March with one wave of flowers. Further evaluation of these conditions is needed.

To view specific spring weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage ( www.crec.ifas.ufl.edu ). Additional weather data links are also listed. If you have any questions about bud growth initiation and flowering, you can contact me by email (albrigo@crec.ifas.ufl.edu ) or call 863-956-1151.

.


 

3/17/2005

 

FLOWER BUD INDUCTION ADVISORY #20 for 2004-2005-3/17/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Please review the background information in the first advisory if you have not already done so.

Bloom dates of the different waves of developing flower buds are almost on schedule with the ‘Citrus Flowering Monitor' model. The unexpected difference is that for most blocks of trees the first wave had few flowers compared to the second wave, which will be the large bloom. For the past 5 or 6 years of careful evaluation, the first wave of flowers has always been the heaviest, if not the only bloom (2 years). Although no data was taken previously, I don't recall a similar situation ever occurring. The actual bloom dates are about 5 or 6 days behind the prediction, maybe partly due to cool weather and partly due to either a heavy previous crop or leaf loss from the hurricanes. Trees in south Florida that were drought stress during the winter will bloom the end of March as predicted in an earlier advisory.

Prior to 10 years ago, the average bloom date was 15 to 20 March. The past few years it has been 1 March or earlier for the first wave. This year would not have been that much different if the first wave had been strong. It appears that late winter through spring temperatures have been warmer in recent years, but the weather data has not been analyzed to see if there has been a significant difference for the 1960s and 70s compared to the past 10 years.

I expect that this year's bloom dates will put us on a more favorable maturation schedule with processing Hamlins not reaching 14-16 ratios until mid-December or later and Valencias holding on later also. Of course fresh fruit harvests should be later also, but with less chance of early section drying. The weather for the rest of the spring and fall will of course affect rate of maturation, but the starting date is important.

To view specific spring weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage www.crec.ifas.ufl.edu . Additional weather data links are also listed. If you have any questions about bud growth initiation and flowering, you can contact me by email albrigo@crec.ifas.ufl.edu or call 863-836-1151.

.


 

3/22/2005

 

FLOWER BUD INDUCTION ADVISORY #21 for 2004-2005-3/22/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Please review the background information in the first advisory if you have not already done so.

Bloom dates of the different waves of developing flower buds are as confusing as I can remember. Locally, we had a first wave and now have a lot of flowers ready to pop and some to many open depending on the tree, but there are a lot of flowers dragging behind that will not be open before next week. I think it is as much the cool weather as anything else, but the hurricanes and two years of heavy fruit set may be contributing.

I thought the weather might have been warm enough in southern areas to push the bloom out and provide a more concise second wave of flowers. Two reports from that area suggest it is just like here. At least three waves of flowering are being seen. Use of prolonged low irrigation did not result in one late bloom, but rather a delay of the three waves. Perhaps the drought stress level was insufficient to actually stop early bud development. It looks like everyone will still have flowers opening next week. In Desoto County they haven't had enough open flowers to be able to smell the typical orange bloom period. A week of warm weather should really push the pin head flowers along to full bloom. The 8-day forecasts have mid- to high 80s predicted for the latter part of this week as far north as Central Florida. Northern areas may only reach the high 70s. Second wave peak looks like it will be at least 1 to 1 ½ weeks later than the model predicted, which was March 15th.

Dr. Timmer thinks most blocks are ok from PFD if you haven't seen any to speak of yet. However if rains continue this week as predicted and occur again next week, there could be problems if a little PFD is showing this week. You should follow his website and the PFD model recommendations (www.crec.ifas.ufl.edu/timmer).

To view specific spring weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage www.crec.ifas.ufl.edu . Additional weather data links are also listed.

I will be in California until the middle of next week, but If you have any questions about bud growth and flowering, you can contact me by email albrigo@crec.ifas.ufl.edu .

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4/4/2005

FLOWER BUD INDUCTION ADVISORY #22 for 2004-2005-4/4/05

Please review the background information in the first advisory if you have not already done so.

The bloom period is almost over. Locally, mandarin trees still have some popcorn stage flowers, but most are open. Only a few closed flowers remain on Valencias and grapefruit. Many flowers have passed petal fall. The overall flowering level in this last flowering wave is excellent and the supporting flush in this area looks good. The ‘Citrus Flowering Monitor' has not updated its prediction of two waves of flowers in early and mid March. The computer program clearly does not adjust for cooler weather from the last stages of flower development through bloom. Overall, it appears the second wave was 2 weeks later than predicted, but it appeared to be only one week late around the 15 th of March (predicted bloom date). Reports I have gotten from other areas indicate that their citrus was behaving similarly with a last full bloom dates reported at 3/28 and 3/30 in Ft. Meade and Immokalee, respectively, with large tree to tree variation in full-bloom dates. But was this the second or third wave of flowers to occur this spring?

I did not clearly detect a third wave in the Lake Alfred area and none was mentioned in the Ft. Meade report. In Immokalee, they did see three, but they were able to maintain a prolonged period of drought stress, which may have led to three waves rather than stopping the first two. Further work on drought stress intensity required to stop growth is needed.

Mid-bloom for this season may be about 25 March, which is significantly later than in recent years. The cooler than normal weather is also delaying fruitlet drop. Currently, fruitlet numbers on trees I have looked at are very high. We can expect a heavier than usual May-June drop this year. It should start in June with the late bloom. As of now, trees in good condition look like they will set a good crop. Next week we will talk a little about fruit set prospects on hurricane affected trees.

To view specific spring weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage www.crec.ifas.ufl.edu . Additional weather data links are also listed.

If you have any questions about bud growth and flowering, you can contact me by email albrigo@crec.ifas.ufl.edu or phone 863-956-1151.


 

5/6/2005

FLOWER BUD INDUCTION ADVISORY #23 for 2004-2005-5/6/05

NOTICE FOR CITRUS EXTENSION AGENTS & SPECIALISTS AND GROWER NEWSLETTERS 

The following information has been developed as part of the Decision Information System for Citrus. 
L. Gene Albrigo, Horticulturist 
Citrus Research & Education Center, Lake Alfred, FL

Summary of 2004-05 flowering season with initial evaluation of fruit set potential.

This past winter, flower bud induction appeared to be fairly good with accumulation of 830 to over 1000 hours below 68 degrees F before the first wave of buds initiated growth and from 940 to over 1200 hours before the second wave of buds initiated growth. Initiation of growth dates were also about normal (late December and after the 1st week of January).

In spite of this, the first wave (cohort) of flowers this spring was surprisingly small on mature trees, but the overall flowering level in the second wave of flowers was strong. In the previous 5 or 6 years, the first flowering wave has always been the strongest. Perhaps 2 heavy crops (before hurricane reduction this year) reduced carbohydrate levels to the point that much more induction was need for most buds. Before the second wave of flowering, the supporting spring flush was developing strongly. Because of the cool weather, which delayed the bloom date of the second cohort of flowers, the spring leaf flush was more developed when the second flowering wave occurred. Since the leaves are more developed, they should provide more carbohydrates to the developing fruit thereby minimizing fruitlet drop.

Only the South Florida area around Immokalee and La Belle had dry enough conditions in the winter to alter bloom dates by allowing water stress to develop and prevent early flowering. But the bloom date of the second cohort of flowers in this growing area was not different even though soil moisture records indicated that sufficient drought occurred to prevent early flowering. All regions of the state experienced the weak first wave and delayed but strong second wave of flowering. For the southern area, perhaps the weak first wave plus the late second wave masked any influence of drought stress.

The second flowering wave reached full bloom about 10 days later than the ‘Citrus Flowering Monitor System” predicted. The cool weather during the last stages of flower development apparently stopped development, but the flowering model was not sensitive to this effect. Additional programming will be needed this year to make the last stages of development more responsive to cool temperature delays.

Initial fruitlet numbers on many trees look good. Some fruitlet drop is occurring but the first drop wave has been less than usual because of the cooler than normal weather and good soil moisture. Temperature in both Immokalee and Lake Alfred were usually less than 80 degrees F for highs (only 13 and 7 days in 80s in March, respectively) and April was similarly cool with only 2 days reaching near 90 degrees F in Immokalee. Effective rains have occurred almost every week (6/9 and 7/9 weeks, respectively, with more than 1/3 inch of rain and over half the weeks with an inch or more). Since fewer fruit dropped in the bloom period, we can expect a heavier than usual May-June drop this year. It should start in June, rather than May because of the later major bloom. This is to be expected. There is no reason to panic and think all of the fruit are falling off. As of now, trees generally are in good condition and look like they will set a good crop.

On hurricane affected trees that lost many old leaves, strong fall flushes were stimulated that raised many questions about their ability to flower. Also the losses of buds to flushing that otherwise would have flowered caused concern. Most of the fall flush on hurricane affected trees was able to flower, although post Jeanne flush flowered poorly. As for all trees, temperatures and rainfall have favored fruit set and good spring flush development. Most reports from hurricane affected areas indicate trees are rapidly recovery canopy. Since most trees were not pushed over or lost many limbs, it is likely that most trees, even in zone 1s on the West and East Coasts will have a reasonable recovery crop. Although hurricane affected trees will not be back to normal this year, I expect that they will carry a larger crop than many expected. If not too many orange trees are lost to citrus canker this season (about 6,000 acres so far), we may be able to do as well as in 2002-03 when flowering was very poor. Hurricane tree losses are probably less than 2 %. Grapefruit trees, although they had the most severe leaf losses from the hurricanes, should make considerable recovery this year. Flowering and flush recovery reports are fairly good.

Will fruit be smaller this year? A lighter crop could help fruit size, but the cool spring temperatures do not favor better fruit growth and the later bloom may also minimize fruit size if temperatures stay cooler than normal for much longer. The past two years of heavy crops before the hurricanes and leaf losses in the hurricane paths probably reduced available carbohydrates early in fruit growth, when they are most needed. Overall on mature trees, fruit size could likely be smaller again this year as it was last year.

To view specific spring weather data for a location near you, go to FAWN or to NOAA's 8-day forecast in the Weather Links on this CREC homepage www.crec.ifas.ufl.edu . Additional weather data links are also listed. This will be the last advisory for this year.

If you have any questions about flowering and fruit growth, you can contact me by email albrigo@crec.ifas.ufl.edu . Don't phone until after 17 May. If you want to learn more about regulation of vegetative and reproductive growth of citrus consider the classes offered on Monday nights this coming Fall and Spring Term ( 2005-06), at CREC in Lake Alfred and simultaneously by video conferencing at other University of Florida REC locations in the other citrus production areas and in Gainesville.