Flower Bud Induction Header

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

Flower Bud Induction

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2/4/2019

FLOWER BUD INDUCTION ADVISORY #7 for 2018-2019-2/4/19

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

This is a 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: http://disc.ifas.ufl.edu/bloom

If you are not familiar with the website and flower bud induction in citrus you should read the overview section in the first advisory this year.

Induction and flowering status : The Citrus Flowering Monitor System indicates that all Florida citrus areas may have up to two waves of flowers during the normal bloom period.  The model projects a February 27th to March 5th  first wave full bloom with about 680 to 870 inductive hours depending on location, followed by a second wave around March 14th to 23rd with 818 to 990 inductive hours. Generally, the earliest full bloom dates are for the southern areas of Indian River-Immokalee and Umatilla in the north, but the spread for each wave is only about one week.  The second flowering wave is not likely to occur and should be the lighter wave of flowers if it does occur.  Remember that mandarin cultivars bloom about 7 to 10 days later than Valencia.

An estimate of when 10% open flowers will occur is February 15th . This is when psyllid sprays should stop and when bees may be moved into or placed near citrus blocks. Each beekeeper should coordinate this timing with their local citrus growers.

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


  

1/14/2019

FLOWER BUD INDUCTION ADVISORY #6 for 2018-2019-1/14/19

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

This is a 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: http://disc.ifas.ufl.edu/bloom

If you are not familiar with the website and flower bud induction in citrus you should read the overview section in the first advisory this year.

Current status: We’ve had good induction, but continuing cold temperature conditions have slowed down flower bud development slightly. Initiation of growth of the first flowering wave (cohort) occurred with about 680 to 850 hours of inductive temperatures from south to north and a second cohort may occur at least in the south where lower inductive hours have occurred. The predicted full bloom date is now March 1 to 3 for most areas except Umatilla which is still late February (24th).

For psyllid control: In groves in Central Florida we are seeing some bud break, maybe 20 % of trees. If you want to get maximum psyllid control you need to apply an adult psyllid spray as soon as possible, before feather flush is present.

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


 

1/7/2019

FLOWER BUD INDUCTION ADVISORY #5 for 2018-2019-1/7/19

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

This is a 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: http://disc.ifas.ufl.edu/bloom

If you are not familiar with the website and flower bud induction in citrus you should read the overview section in the first advisory this year.

Current status:  We now have December flower bud growth initiation indicated for north, south and western FAWN sites but not Sebring to Lake Alfred. The first wave or cohort of flower buds initiated growth from 20 December in Umatilla to about Christmas in most other areas with 680 to 840 hours of induction, respectively, from south to north citrus areas. The projected bloom dates for this cohort of flowers are now from February 23 in Umatilla to at or near March 1st for most other areas according to the ‘Citrus Flowering Monitor System’. The weather services predict cooler weather this coming week, which should delay flowering a bit pushing the full bloom date to March 1st as of now.

Since the first flowering wave was initiated with only 680 to 750 hours of induction in the south, a second wave of flowering is very likely in the Indian River and Immokalee areas.

If you didn’t apply a flowering enhancement spray of urea or PO3 at the beginning of initiation of the current flowering wave, it is now too late.I don’t advise applying a spray at the beginning of a second wave since over 800 hours of induction will have been accumulated, sufficient for a good two-part spring bloom.

For spring psyllid control:The small amount of flush associated with a little flowering has passed the egg and nymph stage and adult stage psyllids predominate. Bud break of the new spring flush should be about 15 to 20 January so watch carefully and get an adult spray on before feather flush is present. If you wait until you see flush it is too late and the adults have started laying eggs.

For bee keepers. I think the bloom will be delayed until early March and earliest 10 % open flowers will likely be no sooner than mid-February. I will keep you posted on a weekly basis.

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


1/2/2019

FLOWER BUD INDUCTION ADVISORY #4 for 2018-2019-1/2/19

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

FLOWER BUD INDUCTION ADVISORY #4 for 2018-2019-1/2/19

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

This is a 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: http://disc.ifas.ufl.edu/bloom

If you are not familiar with the website and flower bud induction in citrus you should read the overview section in the first advisory this year.

Current status: We’ve had fairly cool weather until late December and currently 750 to 950 hours of inductive(hours <68° F) weather have accumulated from southern to northern citrus areas in Florida. Unlike 2017-18 only the most northern area, Umatilla, has initiation of flower bud growth, whereas the initial cohort of flower buds started development at 630 to 815 hours of inductive hours south to north the past year by this time. The full bloom date for Umatilla is Feb 25th with a projected accumulated hours of 838 according to the ‘Citrus Flowering Monitor System’. The Weather Channel predicts 3 more days in the mid-80s, thru Friday. It is likely that most other citrus locations will have initiation of flower bud growth by Saturday if not sooner.

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


1/3/2018

FLOWER BUD INDUCTION ADVISORY #4 for 2017-2018-1/3/18

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

FLOWER BUD INDUCTION ADVISORY #4 for 2018-2019-1/2/19

This is a 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: http://disc.ifas.ufl.edu/bloom

If you are not familiar with the website and flower bud induction in citrus you should read the overview section in the first advisory this year.

Current Status: We’ve had fairly cool weather until late December and currently 750 to 950 hours of inductive(hours <68° F) weather have accumulated from southern to northern citrus areas in Florida. Unlike 2017-18 only the most northern area, Umatilla, has initiation of flower bud growth, whereas the initial cohort of flower buds started development at 630 to 815 hours of inductive hours south to north the past year by this time. The full bloom date for Umatilla is Feb 25th with a projected accumulated hours of 838 according to the ‘Citrus Flowering Monitor System’. The Weather Channel predicts 3 more days in the mid-80s, thru Friday. It is likely that most other citrus locations will have initiation of flower bud growth by Saturday if not sooner.

The first initiation of growth (first cohort of flowers) was before sufficient induction had occurred to produce a level of flowering for an economic crop except for the northern-most tier of groves. However we now have from 850 to over 1000 hour of induction from south to north plus an additional 130 to 150 hours projected for the following week. There may be enough warmer weather in the southern tier of groves for a second cohort of flower buds to initiate growth after another week, but the Ridge groves probably will be further delayed unless temperatures rise above current predictions. In all cases enough time is occurring between the flower cohorts that they should be visibly distinct on the trees.

I’ll probably provide another update next week if initiation of flower bud growth is indicated by the model for most citrus areas. Important coming dates will be when to spray for adult psyllids before feather flush is present and when the last psyllid spray can be applied before there is danger of harm to bees because of 10 % open flowers. More next week.

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


12/21/2018

FLOWER BUD INDUCTION ADVISORY #3 for 2018-2019-12/21/18

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

FLOWER BUD INDUCTION ADVISORY #3 for 2017-2018-12/20/17

This is a 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: http://disc.ifas.ufl.edu/bloom

If you are not familiar with the website and flower bud induction in citrus you should read the overview section in the first advisory this year.

Due to the holidays this will be the last flower bud development advisory until after the new year.

Current status: Currently there are 570 to 790 hours of inductive hours (<68° F) from south to north. Over the next seven days an additional 90 to 130 inductive hours should accumulate for totals of 660 to 920 from south to north by December 27th. This would leave South Florida groves slightly below an ideal minimum of 700 hours of inductive temperatures but more northern groves should be above to well above this level by midweek.

The weather center temperature forecast for Immokalee indicates there is likely to be 8 days with daytime highs in the 80s starting about midweek next week. These temperatures are likely to initiate flower bud growth of a first cohort of flowers. At 650 total hours there would likely be a later, second, cohort in the South Florida citrus area. In the mid-Florida area only 4 days in the low 80s are predicted which may not be enough warmer weather to initiate growth. The northern tier of citrus should not respond since cooler weather should continue there

The above scenario is fairly typical and generally looks ok for a good bloom this spring. A problem with HLB affected trees is the amount of off-season, winter bloom, that 1) provides new leaves for continued psyllid population maintenance and 2) takes buds away from the normal productive spring bloom. In the Central area where we are monitoring flush and psyllid populations, there is a mix of off-season conditions from block to block. Many blocks have a scattered flush of flowering buds but many blocks have almost none. There are also blocks in which few flowers are showing, but there are still some vegetative only flush with not more than 4 or 5 flowering shoots on the tree. This is not typical of what we have been seeing the past few years where most of the winter flush is with flowers. I have no idea why things are different except that in citrus, in Florida, things are different every year. These conditions, where flush is occurring, are still taking buds away from the spring flowering.

Everyone have a Happy Holiday season; I’ll be communicating with you in the new year..

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


12/11/2018

FLOWER BUD INDUCTION ADVISORY #2 for 2018-2019-12/11/18

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

FLOWER BUD INDUCTION ADVISORY #2 for 2018-2019-12/11/18


This is a 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: http://disc.ifas.ufl.edu/bloom. If you are not familiar with the website and flower bud induction in citrus you should read the overview section in the first advisory this year.

Flower bud induction status in 2017-18 for the 2018-2019 crop In this El Niño winter, cool temperatures are accumulating and rainfall is occurring on the cold fronts as expected. Citrus locations currently have accumulated moderate inductive temperature hours, < 68 degrees F, of 430 to 600 hours from southern to northern areas, respectively. The next 7 days will have low cool temperature accumulation of 100 to 150 hours, south to north. The totals of 530 to 750 hours after this week should be 2/3rd to 3/4th of the total we would like to have for a good economic flower induction level. The following week (10 days out) still looks to be moderately cool with little chance of warm enough temperatures to stimulate bud growth.

Accumulation of cool temperatures and prevention of growth during a fall or winter warm spell is very important for good 2018-19 citrus production. The weather needs to continue to stay cool to prevent early initiation of bud growth, which can occur with daytime temperatures in the mid-80s for 7 to 10 days after accumulated cool inductive temperatures have reached 450 to 500 hours. Fortunately, we have had few continuous days of 80 degree daytime highs and 10 more days of cool weather are predicted by the weather service. Ten cool days will get us to Christmas which is a common date for a warm period to initiate flower bud growth. Continued cool weather until New Year’s day would be even better.

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


11/27/2018

FLOWER BUD INDUCTION ADVISORY #1 for 2018-2019-11/27/18

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

FLOWER BUD INDUCTION ADVISORY #1 for 2018-2019-11/27/18
This is a 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: http://disc.ifas.ufl.edu/bloom

If you are not familiar with the website and flower bud induction in citrus you should read the overview section below the current status paragraphs.

In the on-line version you can shift from one FAWN weather site as soon as the results from your previous query is displayed. All citrus area FAWN sites are in the menu.  The total accumulated hours is now listed as is the forecast (projected) hours to be accumulated the following week.  We now have an estimate procedure for the number of days before full bloom for the start of vegetative flush and 5-10 % open flowers to aid in managing psyllid sprays for the bloom period and the most active bee period.  See the last section for more details on this information. The last section evolved from a Citrus Research and  Development Foundation supported effort.

Flowering related to the current 2018 -19 Crop Estimate– During an El Niño neutral winter, cool temperatures (less than 68 o F) followed a normal development pattern with adequate flower bud inductive hours, about 800 in Central Florida. A December warm period initiated growth of the first set of flowers that bloomed in late-February to March 1st as a fairly uniform bloom with a light earlier flowering due to HLB stress conditions producing this stress bloom. Almost no second cohort of a later bloom occurred. Most growers were anticipating a better crop than in the previous two years which was supported by the NASS crop estimate in October of 79 million boxes of round oranges.

Flower bud induction status 2017-18 for 2018-2019 crop- This is going to be a La Niña winter with lower than average cool temperature accumulation and lower rainfall.  Currently, citrus locations have accumulated low inductive temperatures, < 68 degrees F, of 140 to 188 hours from southern to northern areas, respectively. The next 7 days will have low cool temperature accumulation with less than 20 to 65 hours, south to north. This is a slow start as would be expected for a La Nina year, but rainfall has been higher than expected. Accumulation of more cool temperatures and hopefully a quick turn to cooler temperatures is needed to prevent early flushing, off-season flowering and good spring flowering for 2018-19 citrus production.  

Current flower bud induction status for 2019-2020 crop – This is going to be an El Niño winter with higher than average cool temperature accumulation and more rainfall. Currently, citrus locations have accumulated low inductive temperatures, < 68 degrees F, of 230 to 370 hours from southern to northern areas, respectively. The next 7 days will have cool temperature accumulation of 60 to 80 hours, south to north. This is a reasonable start.

The current level of induction, at least 250 hours, is about 1/3 of the desired minimum low temperature accumulation. When we reach 450 to 500 hours, a warm temperature period can stimulate terminal buds to initiate growth with the risk of 1) early spring flowering and 2) multiple cohorts of flowers during the spring flowering period. We will monitor for this eventuality, but due to heavy preharvest fruit drop associated with HLB infection, growers have few options to prevent early flowering, see background section.

During the previous 6 years with chronic HLB, Florida citrus trees have had early to late winter flowering due to water stress induced flowering because of poor root systems and infrequent irrigation in the fall. Several IFAS faculty, notably Drs. Davie Kadyampakeni, Kelley Morgan and myself, are advocating daily, lower volume, irrigations to minimize fall water stress. Fewer off-season flowers results in more buds available for normal winter cool temperature induction and spring season flowering. Reduced off-season flowering also reduces off-season leaves for psyllid development. Growers should be diligent with their practices of frequent irrigation at least until cooler winter temperatures prevail on a consistent basis.

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, 19 o C). Periods of high temperatures in winter can then initiate bud differentiation which after sufficient days of warm winter-springtime temperatures leads to bloom. The meteorologists predict that this winter in Florida probably will be a ENSO-El Niño year, below average temperatures and higher than average rainfall. Under these conditions, enough hours of low temperatures < 68 degrees F. will usually accumulate to induce an economic level of flower buds, but intermediate warm periods during the winter lead to multiple flower cohorts and a very prolonged bloom. Other conditions that can interfere with good flower bud induction include: 1) exceptionally high previous crop or 2) excessive leaf loss from hurricanes, freezes or other causes (canker, HLB) where tree recovery is not complete. Excessive leaf loss leads to low carbohydrate levels in developing buds which reduces their ability to become flower buds and/or to set fruit. Hurricane Irma resulted in some leaf loss that adversely depleted carbohydrate levels. Further, continual warm weather after leaf loss stimulates new shoot growth. These new shoots would otherwise be potential flower buds in the spring thus reducing the next years crop potential. Another concern in some years is the greater possibility of a freeze. Freezes are more likely in La Nina or neutral weather years. The biggest current concern will be reduced available carbohydrates in weaker trees because of HLB.

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 800-850 hours below 68 degrees F. If the crop load is light and trees are healthy, 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 from 80 to 85 degrees F., can trigger growth (bud swelling) if a minimum total hours of low temperatures have accumulated (350-450 hours < 68 degrees F). Later in the winter when the accumulated cool temperature induction hours are higher, fewer days and lower daytime highs (5-7 days, 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 and evaluated with the Citrus Flowering Monitor System using data 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.htm. The Weather Channel has a 10 day forecast available also. These are easy ways to see if a warm period, which could trigger flower bud growth, is predicted for your specific area in Florida.

Some terminal flower buds will be induced in the range of 350 to 450 accumulated hrs < 68 degrees F. Warm events after these levels of induction are met 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 irrigated. 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 early spring, late winter 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 early December. Then after more cool temperatures additional flower buds are induced and a later warm period starts their growth and repeats of this temperature cycle result in multiple blooms, usually two to three, but all in the mid-February to early April normal spring flowering period.

Presently, the only management tools available to eliminate or reduce the chance of multiple blooms are sufficient drought stress to stop growth or a timely gibberellin (GA) spray near but before the initiation of the first wave of bud growth. 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 in healthy trees. 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 water 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 of cool periods. Sufficiently cool temperatures (< 68 o F maximums) 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. (See water stress from HLB and mature fruit retention issues in next paragraph.)

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 pre-HLB studies, Valencia trees in Central Florida had good flowering and no apparent impact on current crop when irrigation was stopped in early December and resumed in the spring. Unfortunately, with poorer root systems associated with HLB, trees are likely to be under some water stress much of the dry fall, even with normal irrigation practices.  This has led to unwanted early flowering (late December to early February) due to water stress induction of flower buds.  For this reason plus associated preharvest fruit drop, drought stress management of flowering is not a good option for HLB infected trees, essentially all citrus trees in Florida.

That leaves application of a gibberellic acid (GA) spray as an alternative.  GA will reverse induction and knock out a weak first flower initiation, but it has to be applied just before or as the warm period starts.  If induction level is above 600 or 650 hours the spray will not completely stop all of the flowering, but a more concentrated flowering should occur after the second warm period.  Discussion of results from fall GA sprays to reduce off-season winter flowering associated with HLB will be in the next advisory.

Much of what has been stated above has now been incorporated into the ‘Citrus Flowering Monitor Expert System for Florida’.  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. The left side line tracks low temperature accumulation. If the current crop is very heavy, then more cool induction is needed to compensate for the crop load effect. If the current crop is lighter or tree condition better, then fewer total cool temperature hours are needed for an equal level of flowering. The right side line(s) track flower bud initiation and development to full bloom. Recommendations (text below graph) consider the current crop level in assessing when action should be taken to try to reduce or to enhance initiation in the flower bud development process. The system is available on-line: http://disc.ifas.ufl.edu/bloom . The on-line version can be used to evaluate any previous year back to 1998-99 by putting in a March or April date for a FAWN location of your choice in the menu. This program does not work if May through September dates are entered.

1999-2000_bloom

Additional advisories will follow this preliminary one, roughly bi-weekly, 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.
Additional uses of the ‘Citrus Flowering Monitor System-

  1. Timing initial spring psyllid spray – Initial bud growth in the spring is indicated by the ‘Citrus Flowering Monitor System’. Until the leaves in those buds are visible (begin to unfold) there is no available plant material for adult psyllids to lay eggs and begin the cycle of a new population.  An adult psyllid spray at this time is an effective way to disrupt the new psyllid population cycle and this timing provides much longer control.  Bud break usually occurs about 2 to 3 weeks after initiation of bud growth (beginning of differentiation). You can follow this with the ‘Citrus Flowering Monitor System’.  Most growers cannot cover all of their citrus blocks quick enough with their ground equipment to get all blocks covered before feather flush is available for adult psyllids to lay eggs.  An aerial application is more likely to meet the required timing even though canopy coverage is not as efficient.  As this time approaches in December-January  further details will be posted.
  2. Appropriate time for bee movement into and out of citrus blocks – The ‘Citrus Flowering Monitor System’ can also be used to judge when 10 % open flowers is likely to occur.  In 2015 and 2016, early and late flowering years, respectively, 54 to 53 days occurred from initiation of bud growth until 10 % open flowers.  Further, when 17 years of flowering data were evaluated it was determined that the weeks until bloom from initiation of bud growth varied by 3 weeks  and mean weekly temperatures for the first 4 weeks determined the length of the flower development period.  Based on the data available, it appears that the time until 10 % open flowers should increase about 7 days per each 5 o F above 60 o F.  We will evaluate these timing predictions for growers to stop spraying more effective, harsher, pesticides for psyllid control and for beekeepers to move bees into citrus this coming spring.  Bee removal timing appears to be about 11 to 15 days after full bloom.  Again we will visit this issue as the model indicates that growth of the first wave of spring flowers has been initiated.

See a previous background introduction for previous important yield responses to cool temperatures: FLOWER BUD INDUCTION ADVISORY #1 for 2012-2013.
If you have any questions, please contact me (albrigo@ufl.edu).