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EXTENSION Beiy Times
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VoluIe 11, Isse1Dc
Se d Anr I
Spotlight on Diagnosis Jim Mertely and Teresa
It has been a busy month at the UF Strawberry
Diagnostic Lab. Over 30 samples have been received since
the beginning of November. Twenty of these have been
diagnosed with various anthracnose diseases. The
anthracnose fungus Colletotrichum acutatum was identified
on 10 samples early in November. These stunted transplants
were only a few weeks old and failed to establish properly
due to infections in the roots, crowns, or buds. C. acutatum
is particularly aggressive towards young plants that are
infected in the nursery and stressed in the field by hot
weather and transplant shock. More robust plants that had
suddenly wilted or collapsed began arriving later in
November. The crowns of these plants were extensively
rotted or discolored internally. While several different
pathogens can cause such symptoms, Colletotrichum
gloeosporioides was isolated from the majority of these
plants. Surprisingly, C. fragariae was also identified from a
few specimens. Both are anthracnose fungi commonly
associated with crown rot disease in strawberry.
Several cases of sting nematode (Belonolaimus
longicaudatus) damage were unexpectedly diagnosed in
November (sting nematode damage is more typically found
in the spring). The sting nematode is a large and damaging
nematode that feeds near the root tips, causing stubby root
symptoms below, and stunting above. Infested plants are
often clustered in fairly well defined patches in the field.
Stubby root symptoms
are a sign of sting
Wind and Humidity as Factors in Freeze Protection
with Sprinkler Irrigation Craig Chandler
The following article was adapted from a scholarly
paper written by Dr. Paul Lyrene, Professor of Horticultural
Sciences at the University of Florida, and published in the
1996 Proceedings of the Florida State Horticultural Society
(Vol. 109; pgs. 215-220).
Through several processes, wind greatly reduces the
effectiveness of overhead irrigation in freeze protection. It
reduces the uniformity of water application. It moves the
warmed air out of the field and replaces it with colder, drier
For many years blueberry growers in Florida
have used information provided by UF/IFAS to predict
the water application rate required for cold protection
under different wind and temperature conditions. This
information indicates, for example, that 0.12 inch of water
per hour will prevent freezing of flowers if the air is 22 F
and there is no wind, whereas 0.5 inch per hour would be
needed at the same air temperature if the wind is 5 to 8
miles per hour.
Twenty years of experience with freeze protection
of blueberries in Florida under various wind and
temperature conditions have proved the utility of the
information provided by UF/IFAS, but have also revealed
that protection on windy nights is sometimes far better or
worse than expected. The principal reason for these
discrepancies is believed to be variations in humidity.
Growers need accurate temperature, wind speed,
and relative humidity or dew point information in order to
make the best decisions as to whether water should be used
on a particular night. A standard index for comparing the
moisture content of the air during various freezes is
needed. Moisture indexing would help growers predict the
effect of using their irrigation systems during an
impending freeze based on how the systems performed
during previous freezes they have experienced. The dew
point is probably the most useful index. Dew-point
readings for stations throughout Florida are available from
the Florida Automated Weather Network (FAWN) at
FAWN provides useful weather information throughout
the state including dew-point readings.
If there is little wind, the dew point will probably
change little between noon and the following sunrise,
except in frost pockets, where frost formation may reduce
the dew point by several degrees after dew and frost begin
to form during the night. If there is significant wind from
a direction between west and north, drier air may be
moving in, and the dew point may fall substantially during
the night. This is particularly true within 48 hours after
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passage of a cold front. If the dew point is above freezing and
drier air is not moving in, a damaging freeze is unlikely the
following night, except possibly in the worst frost pockets. If
the dew point is below 10 oF and the forecast minimum
temperature is below 26 OF, freeze protection with water will be
difficult if there is significant wind.
Evidence of freeze
The relative humidity at the time the temperature falls
to 32 OF is important because it indicates how much
evaporation will occur when the irrigation system is turned on.
If the humidity is predicted to be quite low at the time the
temperature reaches 32 OF, then water should be turned on (if at
all) before the temperature falls to freezing. On the other hand,
if the humidity is above 90%, it is probably safe to let the
temperature fall to 32 OF before turning on the water.
Normally on a radiation-freeze night, the temperature
falls rapidly until it is within several degrees of the dew point.
When the relative humidity reaches 96%, further temperature
fall is likely to be slow, because of the heat released as water
vapor condenses into dew or frost.
Another consideration makes dew point temperature
important in protecting strawberry flowers from a radiation
freeze. On clear nights with no wind, exposed flowers, berries,
and leaves that are not hidden inside the bush or shaded by
other leaves become colder than the air. If the humidity is 90%
or greater, frost or dew keeps plant parts from becoming more
than 3 OF colder than the air. However, if there is no sign of
wind, dew, or frost, flowers and berries can become as much as
9 OF colder than the air. If the dew point is below 26 OF on a
calm night when a radiation freeze is expected, sprinklers
should be turned on before shelter temperatures fall below 34
Air masses, which, in Canada, had temperatures as
low as -40 OF and dew points even lower can arrive in Florida
within 3 or 4 days. Although their temperatures rise rapidly as
they move south, their dew points rise less rapidly, since little
water is available for evaporation between Canada and Florida
during the winter, transpiration from dormant plants is
minimal, and the coldness of the air reduces evaporation.
Thus, Canadian air is normally very dry when it arrives in
Florida. Exactly how dry is a matter of great importance to
growers who are trying to protect flowers and fruit on a clear or
For a discussion of 1) terms relating to atmospheric
moisture content and 2) the effects of sprinkler irrigation on air
temperature (also adapted from Dr. Lyrene's paper) please visit
our web site http://strawberry.ifas.ufl.edu.
Reduced Risk Insecticides/Miticides Jim Price
The Reduced Risk Initiative was created by the
US Environmental Protection Agency (EPA) to enhance
the development, registration and use of conventional
pesticides that may be more favorable relative to human
health and to the environment than existing pesticides.
Two of these, Acramite miticidee) and Spintor
(insecticide), are now available for strawberry
production and an additional reduced risk miticide,
Mesa, is expected soon. Oddly, the reduced risk
designation is never indicated on the product label. The
designation is available only to new pesticides, leaving
older but perhaps favorable conventional pesticides
without the designation.
To obtain the reduced risk status, a new pesticide
must possess at least one of the following
1. Low risk to human health
2. Low toxicity to non-target organisms
3. Low potential to contaminate the environment
4. Enhance the use and reliability of integrated
pest management (IPM)
Acramite and Spintor conformed to the
requirements for designation and were treated with a
high priority by the EPA during the registration process.
Even though they possess this designation, each is toxic
and must be handled according to the product label.
The strawberry industry benefits from the Reduced
Risk Initiative in that so designated pesticides can be
registered more quickly than others and because less
hazardous pesticides become available.
Strawberry Culture under Protective Structures
Part II. Biological Control of Pests Dr. Daniel
Cantliffe, Dr. Silvia I. Rondon, and Ashwin
Strawberry is an intensively cultivated high
value crop that requires large inputs of pesticides. The
Biological Control Laboratory of the Protected
Agriculture Project has conducted a series of
experiments, in cooperation with Dr. Jim Price of the
Gulf Coast Research and Education Center, to determine
if the commercial production of strawberries using
biological control agents and minimal pesticides is
possible. Through early detection of arthropod pests and
the release of beneficial insects we intend to minimize
the use of insecticides on strawberries. Reduction in
chemical dependency will provide for safer human and
environmental health and could reduce the production
costs for the grower.
Three predators, the lady beetle, Coleomegilla
maculatafuscilabris DeGeer, the big-eyed bug,
Geocoris punctipes Say, and the minute pirate bug,
Orius insidiosus L. are being evaluated as potential
biological control agents against pests such as the melon
aphid, Aphis gossypii Glover, the two spotted spider
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mite, Tetranychus urticae Koch, thrips, white flies, and sap
beetles. All beneficial are being provided by a commercial
beneficial supplier, Entomos LLC (Gainesville, FL).
Geocorispunctipes, the "big -eyed bug"
(Picture courtesy P. Blanchart).
Feeding behavior, effectiveness, choice, and
functional response studies are being conducted to obtain
basic information regarding the use of predators in order to
determine the application rate of beneficial insects needed for
greenhouse and field situations. Ongoing and future research
will determine the effectiveness of these predators to control
pests on strawberries grown commercially in greenhouses as
well as open fields. Farmers will benefit from the adoption
of this integrated approach because of potential reduction in
cost of production and increase in returns, especially if the
fruit can be sold under a 'reduced pesticide' or 'pesticide
free' label. With the information which we have obtained so
far from our laboratory and greenhouse experiments, we will
be able to establish trials on growers' fields in the 2003-04
season and test our findings. For more information contact:
Dr. Cantliffe djc@.mail.ifas.ufl.edu; Dr. Rondon
firstname.lastname@example.org; or Ashwin Paranjpe
2002-2003 Field Research Projects
Plant Pathology Program Jim Mertely, Steve
MacKenzie, and Teresa Seijo
The Plant Pathology Program conducts standard
fungicide trials and specific research experiments. Each of
the three major diseases of strawberry in Florida
anthracnosee, Botrytis fruit rot, and powdery mildew) is
targeted by a separate fungicide trial. The object of these
trials is to evaluate standard and experimental fungicides for
efficacy, and to develop spray programs that maximize
disease control and minimize chemical use. The following
research experiments are programmed for 2002-03:
* Pre-plant dip. Strawberry runner plants from an
anthracnose-infected nursery field were treated with
fungicides and other products before transplanting to
evaluate their ability to protect plants from poor
establishment caused by Colletotrichum acutatum.
* Anthracnose ontogeny. 'Camarosa' flowers and fruit
will be inoculated with Colletotrichum acutatum in
February to determine which stages) of fruit
development are most susceptible to anthracnose fruit
* Plant colonization. Colletotrichum spp.
colonizing the petioles of'Camarosa' will be
monitored at regular intervals over the season in
plants sprayed with Captan or Thiram at weekly
intervals, and in untreated plants.
* Cultivar-Isolate. In early November, selected
strawberry cultivars were inoculated with isolates
of Colletotrichum gloeosporioides to investigate
cultivar-isolate interactions in Colletotrichum
anthracnosee) crown rot disease.
* Cultivar trials. Florida cultivars and advanced
breeding lines are being evaluated for resistance to
anthracnose fruit rot and Botrytis fruit rot in two
* Botrytis post-harvest. The effect of late season
fungicide applications on the post harvest
incidence of Botrytis fruit rot will be investigated.
Breeding & Genetics Trials Craig Chandler
and Jim Sumler
This season we are continuing an active breeding
program aimed at identifying strawberry genotypes that
produce high yields of firm, attractive, and flavorful
fruit. Here are the specifics:
* 4,000 seedlings (stage 1) are being screened for
desirable fruit quality traits.
* 300 selections (stage 2) are being evaluated for
consistency of fruit quality.
* 12 advanced selections (stage 3) are being
evaluated for ease of harvest, production pattern, fruit
size, post-harvest fruit quality, and resistance to
powdery mildew and fruit rots.
* A planting-date trial includes Carmine, Earlibrite,
Strawberry Festival, Sweet Charlie, and FL 97-39
planted on Oct. 2, 9, 17, and 25.
? Trials to evaluate Aromas, Camarosa, Carmine,
Earlibrite, Strawberry Festival, Gaviota, Sweet Charlie,
Treasure, FL 97-39, and FL 99-56 for resistance to
Botrytis fruit rot and anthracnose fruit rot.
Experimentation of the Plant Physiology
Program -John Duval and Elizabeth Golden
This is an exciting time for the plant
physiology program. The legislative appropriation for
improvements at GCREC-Dover greatly increased our
research capabilities. The addition of three growth
chambers is allowing us to investigate the effect of
temperature on water consumption, nitrate and mic ro-
nutrient uptake, and plant growth and yield under very
controlled conditions. This information should help us
to develop fertilization and irrigation recommendations
that are based on seasonal weather forecasts (e.g.
specific recommendations for El Niiio and La Nifia
seasons, may be possible). In addition, fieldwork is
being conducted to determine the differences in
fertilization and irrigation requirements between
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varieties. This should help us to better optimize varietal performance. Calcium and sulfur nutrition is being examined to detect
any yield or post-harvest quality response of strawberry. Studies aimed at reducing the amount of water needed for
establishment and increasing early season yields are continuing. These studies, which include the evaluation of transplants that
have been mowed or treated with a promising new chemical growth regulator in the nursery, are in their third and final year.
The impact of mowing appears to be cultivar-specific, and the timing of both mowing and growth regulator applications is
critical to success, but these cultural practices appear to have the potential to provide substantial reductions in establishment
time without significantly increasing costs or compromising yields. A study to determine the effect of planting date on growth
and yielding patterns of advanced selections has been initiated in conjunction with Dr. Craig Chandler's strawberry breeding
program. The long-term goal of this study is to develop planting date recommendations that can be communicated to growers
at the time a selection is named and released. Finally, the on-farm demonstration of gravimetric soil water sensors is continuing
this year. Soil water monitoring can help growers use water more efficiently, thus potentially increasing their fruit yields while
reducing their water usage. If you wish to participate in this study, please contact Dr. John Duval at (813) 744-6630 Ext. 75 or
drop by our research center.
Entomology Program James Price and Curtis Nagle
The Entomology Program is continuing to do research at GCREC-Dover for the 2002-2003 strawberry season and the
following trials have been initiated:
* Biological control of spider mites. Observations will be made on a miticides/predator hybrid plan for spider mite control
where miticides are used early-season and predators are used in time for the spring build-up of spider mites.
* Chemical control of spider mites. Evaluations of new miticide chemistries will be completed.
* Sap beetle control. Innovative methods of introducing chemicals for sap beetle control will be tested.
Other Center News Christine Manley
GCREC-Dover's Drip Irrigation School held November 13th proved to be very successful with nearly 40 participants
attending. We would like to thank the following individuals who made this event a great success: Mitch Flinchum, Univ. of
Florida; Eric Simonne, Univ. of Florida; David Studstill, Univ. of Florida; Ron Cohen, SWFWMD; Kenneth Parker, Chemical
Dynamics; Jerry Nance, Dow Chemical Corp.; and Eric Waldo, Helena Chemicals.
Dr. Craig Chandler was recently awarded the Classic Award
by the Florida Strawberry Grower's Association at their annual
awards banquet, "Florida Strawberry Jam 20". With the
presentation of this award, which is one of the top honors
presented by FGSA, the industry recognized Dr. Chandler's
many accomplishments. During his acceptance speech, Dr.
Chandler made a point of thanking Jim Sumler, a biological
scientist at GCREC-Dover, for all the time and effort he has
contributed to the breeding program, as well as his wife,
Lynda. Congratulations, Dr. Chandler!
The use oftrade names in this publication is solely for the purpose ofproviding
specific information. It is not a guarantee or warranty of the products named, and
does not signify that they are approved to the exclusion of others ofsuitable
composition. Us2 pesticides safely. Read and follow directions on the manufacturer's
The Institute of Food and Agricultural Sciences is an equal
opportunity/affirmative action employer authorized to provide research,
educational information and other services ody to individuals and institutions
that function without regard to race, color, sex, age, handicap, or national origin
California Dreaming... Faculty and staff gave a
fond farewell to Dr. Dan Legard of the GCREC-
Dover Plant ,iil, i ..- Program. Dr. Legard will
be moving to California and starting a new
position with the California Strawberry
Commission as their Director of Research and
Education. If you wish to contact Dr. Legard,
please call Christine at GCREC-Dover.
Good luck and best wishes, Dan!
A monthly newsletter of the University of Florida Institute of Food and
Agricultural Sciences, Gulf Coast Research and Education Center, and
Florida Cooperative Extension Service
Gulf Coast Research and Education Center
13138 Lewis Gallagher Road, Dover, FL 33527
(813) 7446630 SC512-1160
Website http//strawberry ifas ufl edu
Editor Craig Chandler (ckc. ufl edu), Design, Layout & Distribution
Christine Manley (cmanlevyauf I edu), Director Jack Rechcigl