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

Select date

 

2/1/2018

FLOWER BUD INDUCTION ADVISORY #6 for 2017-2018-2/1/18

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 have excellent induction, but continuing cold temperature conditions have slowed down flower bud development.  One warm event occurred around December 14 to 23 and another generally about January 9 to 19 depending on location.  Initiation of growth of the first flowering wave (cohort) occurred with about 630 to 800 hours of inductive temperatures and the second cohort occurred with about 800 to 1400 hours of induction depending on location.  The River had only the second timing of flowers initiated according to the Citrus Flowering Monitor System.  Overall citrus groves have very good levels of induction and most areas should have at least two waves of slightly overlapping flowering cohorts. 

Full bloom dates are now projected to be from February 18 to March 1 and a second from March 13 to 29 depending on the area.    In two severely declining Valencia groves near Lake Alfred the first wave is scattered over the trees, and this wave is mostly at the pinhead stage.  Valencia groves examined near Ft. Meade were in better condition but still showed a scattering of new flush with pinhead flowers.  A few popcorn to open flowers were observed from earlier off-season flower buds.

Off-season flowering: Open flowers and popcorn stages were observed on earlier visits to blocks from Lake Alfred to Frostproof and additional flowers are still showing up.  Valencia trees appeared to have more of this than Hamlin, but numbers were low and scattered in all cases.  I have not detected a light flush of these growing flower buds this winter that we have seen in previous winters.  Perhaps the hurricane, uneven leaf loss and uneven stresses on the trees are contributing to the less even patterns for both off-season and the first spring cohort flowering.

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


1/17/2018

FLOWER BUD INDUCTION ADVISORY #5 for 2017-2018-1/17/18

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 #5 for 2017-2018-1/17/18

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.

The on-line version has been updated so that you can shift from one FAWN weather site to another without back tracking. More FAWN sites have been added to the menu. Another added feature is that the total accumulated hours is now listed as is the projected hours to be accumulated the following week. The Immokalee site is not working properly. Computer technical people are trying to fix the problem.

Current status: We now have December flower bud growth initiation indicated for all sites except the Indian River. The first wave or cohort of flower buds initiated growth about mid-December with 630 to 780 hours of induction, respectively, from south to north citrus areas. Palmdale and perhaps Immokalee initiated growth a little later. The projected bloom dates for this cohort of flowers are now from February 21 to 24, except for March 4 and 16 for Lake Alfred and Palmdale, respectively, according to the Citrus Flowering Monitor System. Again this year, the bloom dates do not follow a sequential date pattern from south to north. There have been an additional 500 inductive hours since the first flowering wave was initiated. The weather service predicts an additional 140 hours of inductive temperatures this coming week, with most areas having 3 days of cooler temperatures, one at or near freezing.

Since the first flowering wave was initiated with only 630 to 750 hours of induction, a second wave of flowering is very likely. A second flower bud cohort is indicated for Arcadia and Mayo (I have an interested grower there). It is likely that all areas will have two cohorts of flowers. It is also likely that the full bloom dates will be a little later than now indicated because of the consistent cool weather through January. The model has probably not caught up yet and the next three cold days should also slow down bud development.

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 has been accumulated, sufficient for a good two-part spring bloom. I know some of you sprayed. Tell me if I'm wrong about it probably not helping.

Last week we saw a little bud swell for the coming spring bloom and a small amount of flush and bloom from earlier off-season growth.

For spring psyllid control: The small amount of flush associated with a little flowering had a few nymphs and eggs.

For bee keepers. I think the bloom will be delayed until March and earliest 10 % open flowers will likely be late February. I will keep you posted on a weekly basis.

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 2017-2018-1/3/18

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.

Current Status: We finally got cool weather in late December, but the initial cohort of flower buds started development at 630 to 815 hours of inductive hours south to north. In general this bud development started around Dec 16 to 18 with Lake Alfred being a little later. The full bloom date is projected to be about February 20 to 23, but the colder weather we are experiencing will probably delay the full bloom date. This week i'll try to determine how much delay will occur and report on the probable delay next week.

The FAWN weather data for Immokalee has not been in-sync with the flowering program website. Hopefully, that problem can be fixed this week.

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.

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


12/20/2017

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

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.

Current induction status: The cool weather predicted until Christmas is not materializing. We have accumulated minimum levels of induction temperatures, accumulated 570 to 855 hours of cool, inductive temperatures (< 68° F) from south to north, and an additional 90 to `100 hours may accumulate in the next week.  However, this week is expected to have highs in the 80s, which may trigger the initiation of development of the first wave of flower buds for the spring bloom. 

What can you do? 

You should follow the Citrus Flowering Monitor Model on line through this weekend and Christmas day to see if it indicates that a cohort of flower buds has started differentiation.  We will have inductive temperatures after Christmas and at worse we will just have two identifiable cohorts of flower buds that extend the bloom period longer than desirable.

If the first cohort of flowers does begin to develop this week, then ideal first spray for psyllids could be early in January (8th to 10th maybe) and 10 % own flowers could be about 55 days after initiation of bud growth. University of Florida will be closed during holidays so watch on-line expert system (it works on holidays) and expect an advisory first week of January.

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


12/1/2017

FLOWER BUD INDUCTION ADVISORY #2 for 2017-2018-12/01/17

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 2017-2018-12/01/17

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 2017-2018-12/1/17

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.
The on-line version has been updated so that you can shift from one FAWN weather site to another without back tracking. More FAWN sites have been added to the menu. Another added feature is that the total accumulated hours is now listed as is the projected hours to be accumulated the following week. Additionally estimates of the start of bud break for psyllid spray timing and 5-10 % open flowers to aid in managing psyllid sprays and bee movement for the bloom period will occur with the first initiation of flower bud growth.

Flower bud induction status in 2016-17 for the 2017-2018 crop- In this La Niña winter, with less cool temperature accumulation and rainfall expected, citrus locations currently have accumulated moderate inductive temperature hours, < 68 degrees F, of 300 to 500 hours from southern to northern areas, respectively. The next 7 days will have low cool temperature accumulation of 30 to 70 hours, south to north. The totals of 350 to 550 hours after another week would be 1/3 to ½ of the total we would like to have for a good economic flower induction level.

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. Unfortunately, we have had several days of 80 degree daytime highs and seven more days are predicted by the weather service. Lows are expected to be at near 60. With the low level of induction so far in southern and central areas, we must hope that an initial set of buds do not start growth. It is too bad we cannot apply drought stress to stop initiation of growth at this time. See the first advisory for why this is dangerous with HLB affected trees.

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


11/08/2017

FLOWER BUD INDUCTION ADVISORY #1 for 2017-2018-11/8/17

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 2017-2018-11/8/17
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 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 2017 -18 Crop Estimate– During a weak La Niña winter, cool temperatures (less than 68 o F) followed a normal development pattern with very adequate flower bud inductive hours, about 1000 in Central Florida. A mid-December warm period initiated growth of the first set of flowers that bloomed in mid-February and subsequent normal inductive temperatures and two warm periods led to two more sets of flowers into early March. Most growers were anticipating a better crop than in the previous two years before Hurricane Irma resulted in heavy drop that reduced the crop to below the previous year.

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.  

During the previous 5 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, including me, 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 population development.  The higher fall rainfall may have helped to reduce tree water stress, but growers should be diligent with their practices of frequent irrigation at least until, hopefully, the current high temperature period ends.

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 Niña year, above average temperatures and lower 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. Hurricane Irma has resulted in some leaf loss that may adversely deplete 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 next year’s crop potential.  Another concern for this and next year is the greater possibility of a freeze as coming season’s freezes are more likely in La Nina or neutral weather years. The biggest 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 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).