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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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11/12/2009

FLOWER BUD INDUCTION ADVISORY #1 for 2009-2010-11/12/09

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 

This is a weekly or biweekly service to our citrus growers posted on the CREC website.  The indicated Expert System on intensity and time of bloom can be accessed at the designated Web Site.

Overview of flower bud induction in Florida – Citrus flower bud induction starts in the fall and usually is completed by early January. Low temperatures first stop growth and then promote induction of flower buds as more hours of low temperatures accumulate (below 68 degrees F).  A period 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 an ENSO-El Niño year, below average temperatures and higher than average rainfall.  Under these conditions, more than enough hours of low temperatures below 68 degrees F. usually accumulate to induce a high level of flower buds.  Conditions that can interfere with good flower bud induction include: 1) several warm periods interrupting the induction process or 2) the previous crop was exceptionally high or 3) leaf loss from hurricanes, freezes or other causes (canker) were excessive and tree recovery was not complete.  Excessive leaf loss leads to low carbohydrate levels in developing buds which reduces their ability to become flower buds.  Except for a few trees with freeze damage, none of these adverse conditions appear to be in play for the coming season’s flower bud induction.

Under normal Florida weather conditions but with a moderate to heavy previous crop, sufficient flower bud induction should be achieved when total accumulated hours of low temperatures exceed 800 hours below 68 degrees F.  If the crop load is light, sufficient flower bud induction may occur after 700-750 hours of accumulated low temperatures.  A warm period of 7 to 12 days, with maximum temperatures > 80 to 85 degrees F., can trigger growth (bud swelling) if a minimum total hours of low temperatures have accumulated (300-400 hours below 68 degrees F).  Later in the winter when the accumulated cool temperature induction hours are high, fewer days and lower daytime highs (75 degrees F.) are required in a warm period to stimulate growth of buds.  Weather information relative to Florida citrus flower bud development for the current and several previous years (back to 1998) can be obtained from the Florida Automated Weather System (fawn.ifas.ufl.edu) for locations near you.  An 8 day forecast from the National Weather Service predicts Florida weather for several sites around the citrus belt for the next week. Find this information at:  http://www.nws.noaa.gov/mdl/forecast/text/state/FL.MRF.shtml.  This is an easy way to see if a warm period, which could trigger flower bud growth, is predicted for your specific area in Florida.

Some flower buds will be induced in the range of 300 to 450 accumulated hrs < 68 degrees F.  Warm events just after these levels of induction result in weak flowering intensity, and therefore many buds remain that can be induced by later cool periods, or these buds may sprout as vegetative shoots if warm weather continues and the trees are well watered.  The first situation results in multiple cohorts of flower buds developing to different bloom dates.  The second condition leads to low flowering-fruit set and excessive spring vegetative growth.  During the years from 1963 to 2003, multiple blooms occurred in over half of the years.  Historically, the time period in which an early warm period (7-12 day) can lead to an initial low number of buds growing and flowering is roughly mid-November to mid-December.  Then additional flower buds developing later results in multiple blooms.  Presently, the only management tool available to eliminate or reduce the chance of multiple blooms is sufficient drought stress to stop growth.   This water stress may be provided by stopping irrigation well before these predicted warm periods occur.  If the warm periods(s) are of the typical 7 to 10 day duration, a coincident short period of drought stress will have little impact on current crop development or quality.  Sufficient drought 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 drought stress condition in citrus trees, buds will not grow in response to high temperatures.   If a warm period has passed, trees again can be irrigated to minimize current crop stress.  Although no weather prediction is guaranteed, rains in the winter usually come on the fronts for cool periods.  Sufficiently cool temperatures after a cold front rain will usually prevent growth even though soil moisture is adequate for growth.  Since winter rains usually occur just before cool temperatures, the chances that drought stress will prevent an early flower bud differentiation event are reasonably good for many warm periods.  Even so, growers in some growing districts have often found it difficult to maintain winter drought stress. 

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 to 8 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.  Soil moisture monitoring can help to achieve these goals.  Prolonged late-fall, early-winter drought may be risky for ‘Hamlin’ or other early maturing cultivars not yet harvested that tend to drop fruit near harvest.  In recent studies, Valencia trees in Central Florida have had good flowering and no apparent impact on current crop when irrigation was stoped in early December and resumed in the Spring.  Much of what has been stated above has now been incorporated into a ‘Flowering Expert System for Florida Citrus’.   Figure 1 represents the different aspects of flower induction as depicted by the software program.  The program gives an average bloom situation represented by the shades of green to white, vegetative to heavy flowering, respectively.   If the current crop is very heavy, then the greener shaded bands should be broader (require more hours for the same level of flowering).  If the current crop is lighter or tree condition better, then the colored bands should be narrower as the level of flowering will be as large with fewer total cool temperature hours. 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.  The system will be available on-line again this year, but a new server location is being set-up.  I will announce its location on our Website when it is available:

1999-2000_bloom 
Bi-weekly advisories will follow this preliminary one and update the reader on accumulating hours of related cool or warm temperatures and other weather effects on flower bud induction.  Methods for enhancing (urea or PO3 sprays) or reducing (GA3 sprays) flowering intensity as conditions and cultivars dictate will be discussed in later advisories.  Read the archived advisories from previous years (link at top of this page) for more background.

Previous responses --  In the winter of 2001-2002 following a good crop, cool temperature accumulation was very slow and few hours accumulated (640 hours), warm temperatures persisted and most buds started to grow by 20 December, particularly in well irrigated blocks, leading to excessive vegetative buds.  This resulted in few buds remaining for a second flowering wave and a small crop occurred in the 2002-03 season.  By late December in the winter of 2002-2003, we had 850 hours of uninterrupted cool inductive temperatures with a low current crop on the trees. The subsequent 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, an excellent fruit set occurred in all round oranges resulting in the highest Florida citrus crop forecast by the Florida Agric. Statistical Service (2003-04 crop).  In the winter of 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.  Even though fruit size was small, it looked like we were headed for a 220 million box orange yield before the 2004 hurricanes significantly reduced the 2004-05 crop.  Since then, we have had Hurricane Wilma in 2005 and a long period of tree recovery from the 2004 and 2005 hurricanes.  Since the hurricanes, flowering levels have been lower and even this past spring peak bloom required more hours and the main bloom occurred later (late March), probably because of continued tree recovery after the multiple hurricanes.  For the 2008-2009 crop season, accumulated hours below 68 degrees F were more than acceptable by the second warm period (over 1000 hours) but flowering and crop per tree was still low resulting in an estimate of only 134 million boxes of oranges.  This low yield probably indicates that the trees still were not fully recovered from hurricane effects.  Some details of the hurricane effects can be reviewed in the 11/01/2006 summary-introduction for the previous year’s flower induction cycle.

Current status for 2009-10 Fall-Winter -- The light to medium crops and general tree recovery without a hurricane should lead to a more typical flowering response next spring in Florida.  This is supposed to be an ENSO-El Niño winter with above average cool temperature accumulation.  Warm periods can interrupt the accumulation process and higher than average rainfall could make it more difficult to impose drought stress to prevent an early flowering wave.  Currently, citrus locations have accumulated low temperatures < 68 degrees F of 75 to 300 hours from southern to northern areas, respectively.  The next 8 days will be good for cool temperature accumulation with another 70 to 90 hours.  Continued accumulation of cool temperatures and prevention of growth during a winter warm spell are important for good 2009-10 citrus production.  Therefore, start to monitor irrigation amounts so drought stress can occur if a warm period occurs between November 20 and Christmas or occurs before reaching an acceptable level of over 750-800 hours.  Prepare to make groves relatively dry by withholding irrigation if a warm period is predicted.  Keep track of induction hours in your area and watch for the next advisory.

If you have any questions, please contact me (albrigo@ufl.edu or phone 863-956-1151)


11/24/2009

FLOWER BUD INDUCTION ADVISORY #2 for 2009-2010-11/24/09

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 Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data

Current Status for 2009-10 fall-winter --  Improved tree condition of non-HLB affected trees since the 2004-05 hurricanes should be promising for good flowering next spring if sufficient cool weather accumulation occurs.  Through November 22nd, citrus locations had accumulated low temperatures (< 68 degrees F) of 180 to 440 hours from southern to most northern areas, respectively.  The next 8 day forecast from NOAA calls for moderately cool temperatures, particularly Friday and Saturday with another 85 to 120 hours below 68 degrees F accumulating.  By next week, the most northern FAWN site for citrus should have about 560 hours. The warmer southern areas will have about 300 hours. These values are 160 to 200 hours below last year, but similar to the previous year.

After the two cooler days at the end of the week, the trees will be fairly susceptible to growth stimulation during a warm period if soil moisture is adequate.  The southern, central and northern citrus areas will take another 5, 4 and 3 weeks of moderately cool weather, respectively, to reach a minimum adequate flower bud induction level.  Until that time, prevention of growth during a winter warm spell is very important to prevent initiation of early bud growth.  Therefore, continue to monitor and reduce irrigation amounts so drought stress can easily and rapidly occur if a warm period occurs between now and Christmas.  Maintenance of water stress during this period also is an alternative to having sufficient cool temperatures for flower bud induction.  In recent studies, field trees held under some water stress had more flowers than trees irrigated during the winter.

At the very least, prepare to make groves relatively dry by withholding irrigation if a warm period is predicted.  Keep track of induction hours in your area and watch for the next advisory. See last week’s background advisory for additional irrigation details.

The other side of winter conditions is concern for a freeze.  In this El Niño ENSO winter, freezes are less likely.  As long as the Jet Stream flow is mostly from West to East across the southern half of the US, no rapid Arctic Express cold air movement into Florida is likely.  Check the Weather Underground on the CREC Weather links for easy access to Jet Stream patterns.

There are several useful Websites to follow weather forecasts.  The Florida Agricultural Weather Network (FAWN) now has an easy access function to the NOAA 4 day forecast, just type location and click.  Alternative, an 8 day forecast can be viewed by going to www.crec.ifas.ufl.edu and click on resources> weather> 8-day forecast.  Additionally, 10 day forecasts by city or zip code can be obtained from the Weather Channel, also in the CREC weather links.  Remember during this critical period to view FAWN, use the on-line monitor site, when available, and the NOAA 8 day forecast.  In the meantime, I will post weekly advisories.  In order to prevent bud growth, trees should be slightly stressed if a warm period (7-10 days with maximum temperatures above 85 degrees F.) is predicted.

If you have any questions, please contact me (albrigo@ufl.edu or phone 863-956-1151).


12/03/2009

FLOWER BUD INDUCTION ADVISORY #3 for 2009-2010-12/03/09

Please review Advisory #1 for this year if you have not done so.  Besides background, it provides web site links for weather data.  See below for website for the Flower Monitoring Program (FMP)

Current StatusCool weather accumulation has continued and now it would be easy to stimulate flower bud growth and differentiation if a warm period were to occur.  Fortunately, warm weather is not predicted for the next 7 to 10 days.  The (FMP) indicates that 300 to 370 hours of cool temperatures have accumulated in southern citrus areas, 400 to 460 hours in central areas and 500 to 600 hours have accumulated in low, colder western areas (ONA) to the more northern locations.  The next 8 day forecast from NOAA calls for moderately cool temperatures and another 70 to 140 hours below 68 degrees F should accumulate from south to north.  This will leave the East Coast and Immokalee locations with a little less than have the minimum requirement or at about 350hours.  The Central areas will have about 60 % of a good induction level (good equals 800 hours), while in another 7 days, the northern areas should have a minimal acceptable level of cool temperature accumulation or 700 hours.  The cool fronts Thursday and this weekend will keep soil moisture high, but the cool weather will prevent any likelihood of a warm period for the next 10 days.

The Flowering Monitor Program is now on-line for those who wish to use it.  Go to: http://orb.at.ufl.edu/DISC/bloom .  The number of current hours below 68 degree F is correct, but it is not translating the NOAA 8 day forecast correctly and is estimating too many cool hours over the next week

I will continue to provide advisories weekly until this critical period until Christmas ends and we have sufficient flower bud induction or are faced with an early warm period that will initiate early flower bud development. If you have been spraying urea or PO3 at the beginning of the first warm period, particularly when total hours are marginally low, you should have product on hand.

In this El Nino ENSO winter, freezes are less likely.  The Jet Stream flow should remain mostly horizontal from West to East across the southern two-thirds of the US so that rapid Arctic Express cold air movement into Florida is not likely.  Check the Weather Underground on the CREC Weather links for easy access to Jet Stream patterns and watch it carefully over the next month for any significant change to a southern dip that can easily lead to freezing temperatures in Florida.  I will report my assessment of this as we approach Christmas and the most likely freeze-hazard period. 

There are two useful Websites to follow weather forecasts.  The Florida Agricultural Weather Network (FAWN) now has an easy access function to the NOAA 4 day forecast, just type location and click.  Alternative, an 8 day forecast can be viewed by going to www.crec.ifas.ufl.edu and click on resources> weather> 8-day forecast. 

If you have any suggestions or questions, please contact me (albrigo@ufl.edu or phone 863-956-1151)


12/14/2009

FLOWER BUD INDUCTION ADVISORY #4 for 2009-2010-12/14/09

Please review Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data

Current status for 2008-09 fall-winter – Cool weather accumulation continued at a slow pace this pass week with the more northern locations now at 721 hours (Avalon) and 760 hours (Umatilla), with 600 hours in Central Florida and 475 and 340 hours in Immokalee and Ft. Pierce, respectively.  The southern areas are still at half or less of the desired hours for induction of flower buds.  An additional 60 to 100 hours will be accumulated in the next 7 days.  This will bring the northern areas into the acceptable level induction, but the Central areas will need another two weeks of suitable temperatures and the Southern areas will need longer than that to reach suitable levels.  At least the next 10 days appear to be ok with a cool front coming to lower temperatures into next week.

Regarding freeze risk, the Jet Stream pattern is favorable for minimal risk.  All air flow is west to east with a slight upward movement in the southern area so that the Jet Stream is pulling moist air out of the Gulf into Florida.  This may account for the extended period of humid, wet conditions  (http://www.wunderground.com/US/Region/US/JetStream.shtml).  It has been impossible to dry out the soil so we need to hope for continued moderate temperatures until we can accumulate enough cool weather for good flower bud induction.

There are two useful Websites to follow weather forecasts.  The Florida Agricultural Weather Network (FAWN) now has an easy access function to the NOAA 4 day forecast, just type location and click.  Alternative, an 8 day forecast can be viewed by going to www.crec.ifas.ufl.edu and click on resources> weather> 8-day forecast.  Remember during the critical freeze period to view FAWN, use the on-line monitor site provided in the first advisory and the NOAA 8 day forecast and watch the Jet Stream pattern. 

In order to prevent or delay bud growth now that trees are at a moderate level of induction, trees should be slightly stressed if a warm period (5-7 days with maximum temperatures above 80 degrees F.) is predicted.  Hopefully, we will dry out after the next front so that soil moisture can be controlled through the Christmas-New Year’s Holiday period. 

If you have any questions, please contact me (albrigo@ufl.edu or phone 863-956-1151)


12/24/2009

FLOWER BUD INDUCTION ADVISORY #5 for 2009-2010-12/24/09

Please review Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  This advisory will be the last until after New Year’s weekend as our Center will be closed over the holidays.  I can be reached by email (see below) if you have an important question.

Current status for 2008-09 Fall-Winter – Finally air temperatures expected in an El Niño year have arrived.  It appears that the next 9 days will also be favorable.  Currently, citrus areas have from 460 to 950 hours of cool temperatures (below 68 degrees F).  Through New Year’s Day these numbers should increase to 600 to 1130 from southern to northern citrus areas. Only the Indian River District will be short of a minimum acceptable number of cool hours after next week.  This year the east coast district has had many fewer hours than Immokalee.  In previous years these two areas have behaved similarly regarding cool hours for flower bud induction.  The southern areas would be better off if they received another 200 hours after New Year’s Day.

Finally, a third wave of flowering was projected for Immokalee and the Central Florida area with growth initiated after 1000 to 1150 hours of cool inductive temperatures.  The bloom from this flower bud initiation should peak about March 10th to 14th according to the original Flowering Monitor System prediction.  The model has moved the full bloom date up, but I don’t see it on the trees.  On some trees this third wave is nearly equal in intensity to the second.

Since there will be no update of this advisory until the week of January 4th, you should monitor the temperature forecast next week to be sure that cool temperatures will continue the first week of January.  If warm temperatures are predicted (mid-80s or higher) for the southern areas (Sebring south), you should consider applying urea or PO3 within the first 3 to 4 days of the warm weather to groves in this area.  These products are recommended at 25-28 lbs N as urea or 1½ -2½ quarts (high to low % product) of a phosphite salt per acre.  Other citrus areas appear to be on their way to having adequate cool temperature induction.

Freeze potential– Although El Niño years generally do not produce freezes in Florida there is a deep North to South jet stream trough over the western US.  Currently, the trough reaches Mexico before turning East so that southern air movement is coming across the Gulf of Mexico bring us moderated temperatures.  If that trough moves eastward to the mid-west, we could get freezing temperatures.  You should keep an eye on this development until after mid-January, when freeze probability diminishes. 

Have a Merry Christmas and a Happy New Year.

If you have any questions, please contact me (albrigo@ufl.edu)


1/6/2010

FLOWER BUD INDUCTION ADVISORY #6 for 2009-2010-1/6/10

Please review Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  This advisory will be the last until after New Year’s weekend as our Center will be closed over the holidays.  I can be reached by email (see below) if you have an important question.

Freeze potential– Although freezes have not occurred in Florida’s citrus areas during El Niño years, it appears that string of good luck is broken.  However, the deep North to South jet stream trough over the western US is still turning East over the Midwest or our temperatures would be much lower.  The Jet Stream upper air movement is still coming across the Gulf of Mexico and moderating temperatures.  The trough has moved eastward and the moderation is fairly weak. You should watch this development very closely over the weekend as it will influence how cold it gets with the next front.  You can easily follow the Jet Stream pattern at http://www.wunderground.com/

Current status for 2009-10 Fall-Winter – Cool weather has been continuous for an unprecedented period of time.  Currently, citrus areas have from 691 to 1200 hours of cool temperatures (below 68 degrees F).  The next 7 to 10 days are forecast to stay cold and one week from now even the southern areas will be above 850 hours of cool temperature induction.  This should be very satisfactory for good commercial flowering levels. As of now it appears that we should have one major bloom, but its predicted date is not yet determined.

As soon as warm weather returns the buds will initiate growth very easily.  We have detected a few buds on some trees with bud swell, but the flower monitoring model does not indicate that a significant flowering flush has started to develop.

By the time temperatures get warm enough to push bud growth there probably will be no need to apply flowering enhancement sprays of urea or phosphite salts. 

If you have any questions, please contact me (albrigo@ufl.edu)



1/13/2010

FLOWER BUD INDUCTION ADVISORY #7 for 2009-2010-1/13/10

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 Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  I can be reached by email (see below) if you have an important question.

Freeze damage and flowering– Ok, El Niños have lost their grip on holding off winter freezes in Florida citrus.  However, considerable cold weather occurred the two weeks before the freezes, thus increasing tree cold hardiness.  In Lake Alfred, there does not appear to be too much immediate leaf injury.  Remember as a general rule, if leaves are injured and stick on the tree, there is usually twig damage behind those leaves.  If damaged leaves easily abscise from the shoot, there is a minimum of wood damage.  You can evaluate this within 7 to 10 days.  If damaged leaves stick or abscise at the blade, it takes weeks to determine wood-cambial damage.  The trees should have withstood the temperatures and durations reported (see FAWN station reports). Flowering will not be altered, even if many leaves fall off, unless there was twig and bud damage. 

Freezing temperatures could have been more severe, but the Jet Stream upper air movement is still coming across the Gulf of Mexico and most likely moderated temperatures.  The troughs are now over California and the East Coast with very weak upper air movement over the Midwest.  This may allow for some rapid changes, so continue monitoring upper air movement.  You can easily follow the Jet Stream pattern at http://www.wunderground.com/.  Usually, the freeze hazard is past by January 25th , another 2 weeks. 

Current status for 2009-10 Fall-Winter – Cool weather has been continuous for an unprecedented period of time.  Currently, citrus areas have from 850 to 1400 hours of cool temperatures (below 68 degrees F) from southern to northern citrus growing areas.  The next 7 days are forecast to stay cool and one week from now even the southern areas will be above 975 hours of cool temperature induction.  This should be very satisfactory for good commercial flowering levels. The flowering monitor system has not indicated that flower buds have initiated growth, but it is likely they will start differentiation during the next 7 to 10 days of warmer weather from Sebring south.  Temperature may remain too cool this coming week to initiate bud growth from Lake Alfred north.  As of now it appears that we should have one major bloom.  If bud growth does start in the next week, the earliest bloom date is probably March 10th.  If temperatures are cooler than normal during the next 60 days, the bloom date should be later than mid-March. 

Since 2004, citrus trees in Florida have not been responding well to cool temperature accumulations that were adequate in the past. After a slow start this year, flower bud induction temperature accumulation has been very good and normally flower enhancement sprays would not be called for, as I advised last week.  But if you have experienced weak flowering the past two or three years and were planning on using a flowering enhancement spray of urea or phosphite salts, this next 7 days will be the time to apply it if you have citrus from Sebring south.  Citrus trees in more northern areas are going to have exceptionally high flower bud induction levels, will not initiate bud growth until more than a week goes by and should not need a flowering enhancement spray.

If you have any questions, please contact me (albrigo@ufl.edu).


1/21/2010

FLOWER BUD INDUCTION ADVISORY #8 for 2009-2010-1/21/10

Please review Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  I can be reached by email (see below) if you have an important question.

Freeze damage and flowering - In Lake Alfred, there still does not appear to be very much immediate leaf injury.  Remember as a general rule, if leaves are injured and stick on the tree, there is usually twig damage behind those leaves.  If damaged leaves easily abscise from the shoot, there is a minimum of wood damage.  You can evaluate this within 7 to 10 days.  If damaged leaves stick or abscise at the blade, it takes weeks to determine the extent of cambial damage.  The trees should have withstood the temperatures and durations reported (see FAWN station reports). Flowering will not be altered, even if many leaves fall off, unless there was twig and bud damage.

Current status for 2009-10 Fall-Winter – Yes, according to the ‘flower monitoring system’ we have initiation of differentiation, but the model reports this event from Sebring north, not in the Immokalee or Ft. Pierce areas.  Last we I guessed that ‘temperature may remain too cool this coming week to initiate bud growth from Lake Alfred north’, so what do I know.  I still believe ‘we should have one major bloom’ and the model predicts the full bloom date will be March 20 to 22, depending on the location.  Again, I think that in 1 to 3 days, the model will say that bud growth has started in the southern areas.  Initiation of differentiation started with 1150 (Sebring) to 1450 (Umatilla) hours of inductive temperatures, very good levels of flower induction.  Ft. Pierce and Immokalee are now at 964 and 1136 hours, which are also good.

Next week, we should see that flower bud growth has started in all areas and have predicted bloom dates for the southern areas. 

If you have any questions, please contact me (albrigo@ufl.edu).



1/28/2010

FLOWER BUD INDUCTION ADVISORY #8 for 2009-2010-1/28/10

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 Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  I can be reached by email (see below) if you have an important question.

Current status for 2009-10 Fall-Winter –According to the ‘flower monitoring system’ citrus trees in all growing areas in Florida have initiated differentiation of flower buds. This initiation occurred after 890 (Ft. Pierce) to 1450 (Umatilla) hours of cool induction.  The predicted full bloom dates are March 18 to 20, a 2 day advancement from last week.

About 150 to 200 additional cool hours have accumulated since the initiation of this first flowering wave.  With another 100 hours and then a warm period, the model will predict a second wave.  I don’t believe a second wave will happen because the first wave should account for most of the available buds.  This first wave could be as strong as the 2003 bloom if the trees have fully recovered from their poor flowering responses since the 2004-05 hurricanes.  The buds should be advanced enough to see how the bloom is developing by early March.  As mentioned a couple of weeks ago, at least a few buds should develop earlier than the main wave, but how many is only a guess based on observations that some trees had a few shoots with bud swell.

If you have any questions, please contact me (albrigo@ufl.edu).


2/16/2010

FLOWER BUD INDUCTION ADVISORY #10 for 2009-2010-2/16/10

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 Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  I can be reached by email (see below) if you have an important question.

Current status for 2009-10 Fall-Winter –Due to the cool weather, full bloom dates have been pushed back a little.  The predicted full bloom dates are 16-18 March in southern areas, 20 to 22 March in central areas and 23 to 24 March in northern areas.  These dates may be pushed back a little more if cool weather continues.  If however, the weather finally turned warm, the bud growth is advanced enough that full bloom could come very quickly.

In Central Florida, pinhead flowers can be seen with several leaves in most inflorescences.  Only a few flower-only buds were observed.  Weak trees may be at the popcorn stage.  A scattering of inflorescences were observed that were near full bloom.  These probably relate to the early bud swelling observed and reported on January 6th, report 6.  Although most new growth appears to have a single flower surrounded by leaves, it is too early to tell whether additional flowers are present or not without dissecting the inflorescences.  With the induction levels experienced this year, I would expect the most buds would produce more than one flower.

Unless unusual weather occurs, I will update these reports in two weeks, about March 2.

If you have any questions, please contact me (albrigo@ufl.edu).


3/5/2010

FLOWER BUD INDUCTION ADVISORY #11 for 2009-2010-3/5/10

Please review Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  I can be reached by email (see below) if you have an important question.

Current status for 2009-10 Bloom –Due to the cool weather, predicted full bloom dates have been pushed back about one week in central and northern areas and 3 or 4 days later in southern areas.  The predicted full bloom dates are 19-21 March in southern areas, 25 to 27 March in central areas and 29 to 30 March in northern areas.  These dates may be pushed back one or two more days from the cold weather predicted into this weekend.  The warmer weather next week should advance bud growth and full bloom will come quickly if warm weather continues after next week.  In central Florida daytimes highs are projected to be above 70 degrees F through Sunday, March 14th.

Although a single intense bloom should be the norm, some blocks have little bud push while others have buds out 2 cm with the flowers clearly visible.  This situation exists in Valencia blocks from Lake Alfred to Lake Placid and perhaps in all districts.  A scattering of inflorescences have been observed that were near full bloom, but no healthy trees were seen with a general full bloom.  With the induction levels experienced this year, I expect that most buds will produce more than one flower.  Most buds appear to have leaves as well as flowers, necessary for good fruit set.

Unless unusual weather occurs, I will update these reports in two weeks, about March 19th.

IIf you have any questions, please contact me (albrigo@ufl.edu)


 

4/2/2010

FLOWER BUD INDUCTION ADVISORY #12 for 2009-2010-4/2/10

Please review Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.  I can be reached by email (see below) if you have an important question.

Summary of the 2009-10 Bloom –After excellent flower bud induction levels, flower buds began to develop around January 12-14, 2010.  Initial bloom dates were predicted to be about mid-March, but cooler than normal temperatures, particularly in February and early March, delayed flower bud development.  The final predicted full bloom dates were 17-23 March in southern areas, 25 to 30 March in central areas and 29 March in northern areas.  The actual full bloom dates vary from block to block for a given cultivar in the same area and in general were or are 4 to 8 days later than predicted.  I received a report from Ft. Pierce yesterday that 3 cultivars of mandarin hybrids were at full bloom or 1 or 2 days from that stage.  This is about the same bloom stage as in Lake Alfred and several days after the predicted date of full bloom for Ft. Pierce.  In Immokalee flowers were at the popcorn stage on March 16th on weak trees, and these probably were in full bloom on the predicted date of March 20th.  But healthy trees were a little later.  In the case of Lake Alfred bloom dates appear to be about 7 days later than the predicted date. One block of Valencia is 1-2 days from full bloom, while another block is 4-5 days from full bloom.  The predicted date was March 26th.  The warmer weather this week should advance growth to full bloom quickly.  Again this year, the Flowering Monitor Model did not adjust well to the abnormal temperatures near bloom. On the other hand it still is only about 1 week off the adjusted predicted date.  It did adjust well to the February cool temperatures, just not those in early to mid-March.

Although a single intense bloom should be the norm, the model predicted two bloom waves in Ft. Pierce.  Based on the report from there it appears that the first wave, predicted for March 17th did not develop many flowers and most flowering occurred at the end of March and early April.  This first wave was predicted after 894 hours, but these trees may still be stressed and required more induction than we used to consider as adequate. 

As we near full bloom, a lot of inflorescences are only generative, with no leaves.  Still many buds have leaves as well as flowers, necessary for good fruit set.  Overall this bloom is just within the normal time range, up to April 10th, is an intense bloom similar to the 2001-2002 induction season that led to the very large 2002-2003 crop.  Fortunately or unfortunately, we don’t have so many trees now.  We couldn’t market that size crop with today’s weak demand.  What trees we do have, if they are healthy, should produce a good crop.  We have been working on a method to assess mature tree equivalents to judge how much production potential we have.  We will present that data at the Florida State Horticultural Society meeting this year in Crystal River (http://www.fshs.org/) .

One downside this year was that the winter was cold and photosynthesis was less than for a normal Florida winter, so the new fruit will not start with as high of carbohydrate reserves this spring compared to past years.  The current Valencia crop may be a little short on soluble solids because of this also.  If your trees lost most of their leaves this winter due to freeze damage or because they are in poor health, do not expect them to set a good crop even though they have a heavy bloom.

Unless unusual weather occurs, I will only update this report one more time in June, after the May-June drop.  At that time we should know if the trees are carrying a good crop as predicted.

If you have any questions, please contact me (albrigo@ufl.edu)


6/10/2010

FLOWER BUD INDUCTION ADVISORY #13 for 2009-2010-6/10/10

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 Advisory #1 for this year if you have not done so.  Besides background, it provides web sites to run the Flowering Monitor System on-line and other related links for weather data.

Summary of the 2009-10 Bloom and Fruit set–We had excellent flower bud induction levels with flower buds beginning development in mid-January after about 1250 hours of inductive temperatures in central Florida.  This is 400 more hours than in the 2002-2003 flowering for the 2003-2004 bumper crop.  Other production areas also had proportionately more induction.

Bloom was later than usual for recent years and generally intense as predicted from the inductive levels.  Leafy bloom, which supports good fruit set, was reasonable for the intense flowering.  During bloom and the fruit set period there were frequent rains and temperatures were cooler than normal, both helping fruit set.  We should be in the mid to upper range of fruit numbers per mature tree equivalent.

Fortunately or unfortunately, we don’t have so many trees now.  If you accurately know how many trees we have, you can make a prediction of what the crop will be.

Unless unusual weather occurs this Fall (hurricanes) or Winter (freezes), we should produce more fruit than last year’s prediction.

One last note:  I am retiring on June 30th after 42 years at CREC.  I am not going away and will help someone make the transition next year to providing the basic Flower Bud Induction Advisories on this CREC Website.  My research program will continue with no substantial changes for at least another year.

If you have any questions, please contact me (albrigo@ufl.edu).