Dover AREC Rese
AGRICULTURAL RESEARCH AND EDUCATION CENTER
IFAS, UNIVERSITY, OF FLQRIDA: .
13138 LEWIS GALL GHER ROADt; "'
DOVER, FL 33527
'arch Report DOV-1991-2 i Febr
HIGHLIGHTS OF SIGNIFICANT STRAWBERRY RESEARCH:AND
DEVELOPMENTS FROM AREC DOVER FOR 1i989 AND 1990
Edited by Will E. Waters
INTRODUCTION: Outlined below is a brief summary of most of the significant
research accomplishments from the AREC Dover for 1989 and 1990 for
strawberries. Each entry is listed under one project leader by research
thrust; however, many of the studies involve several scientists. If more
information is desired on any of these projects, please contact the first
research leader listed under each heading.
I. BREEDING, GENETICS, CULTIVAR EVALUATION C. K. Chandler
1. It was determined that the strawberry selection FL 79-1126 could
be an alternative to 'Selva' or 'Dover' (depending on where it is
propagated), and that selection FL 83-37 and FL 84-1932 could be
alternatives to 'Pajaro' and 'Chandler'.
2. Significant interactions were
(nursery location) and genotype
yield and average fruit weight.
detected between propagation site
for total marketable strawberry
3. Several new strawberry clones were identified that produce firm,
attractive and flavorful fruit on relatively small plants that are
easy to harvest. These clones appear to have field resistance to
4. In a variety trial, 11 advanced selections were evaluated along
with 4 standard cultivars. FL 83-37 compared most favorably to
the standards. It had a higher total fruit yield than 'Selva',
'Pajaro', and 'Chandler', and produced fruit of relatively uniform
size and shape, but of only medium firmness. (in cooperation with
Dr. E. E. Albregts).
1. In a 2-year study, Canadian propagated plants started producing
ripe fruit 2 to 3 weeks before Florida propagated plants.
2. A system was implemented to improve the propagation efficiency of
selected clones from the breeding program.
3. A large scale commercial field trial of FL 83-37 was established. d
FL 83-37 is an anthracnose resistant selection that produces
attractive, easy to harvest fruit.
4. The yield and fruit size stability of 'Selva', 'Pajaro', and 3
University of Florida selections were analyzed using data
collected over 5 seasons (1985-90). The analysis showed that none
of the clones, including the named cultivars., had consistently
high marketable yield, and only one clone, FL 81-1350, had
relatively large and stable fruit size.
5. A new field study was established to determine the influence of
planting date on the vegetative and fruiting response of standard
cultivars, new cultivars, and promising selections.
6. A study was conducted (1987-90) to derive estimates.of genetic and
environmental variability for fruit yield, size, and firmness.
Results from this study will be used to design a more efficient
system for selecting desirable genotypes.
7. In a variety trial, 8 advanced selections were evaluated along
with 5 standard cultivars. FL 85-4925 compared most favorably to
the standards. It had a higher total fruit yield than 'Pajaro',
and a total fruit yield not significantly different than 'Selva'
and 'Chandler'. Plants of FL- 85-4925 were easy to harvest and
produced firm, attractive, and flavorful fruit. (In cooperation
with Dr. E. E. Albregts).
II. Biological, Chemical and Mechanical Pest.Management
A. Plant Pathology C. M. Howard
1. It was determined that when injured or noninjured roots of potted
strawberry plants are inoculated with spores or infected root
pieces of Colletotrichum fragariae or Glomerella cingulata (the
fungi that cause anthracnose) no crown rot develops in the plants.
This indicates that crown rot disease does not result from root
infection from infested soil.
2. Spores of Colletotrichum acutatum, Colletotrichum fragariae, and
Glomerella cingulata were injected into crowns of plants in the
fruiting field and it was determined that:
a. C. acutatum does not kill plants but C. fragariae and G.
ETngulata do kill plants.
b. Crown rot caused by C. fragariae and G. cingulata may spread
to a slight degree within the bed.
3. In a comparison of Captan and Bravo fungicides for control of leaf
blight and anthracnose in the summer nursery, it was determined
a. Captan applied 3 times per week gave better control of leaf
blight than Bravo at 1.5 pts/A applied 2 or-3 times per week
or Bravo at 2 or 2.5 pts/A applied twice per week.
b. Bravo at 1.5 pts/A applied 2 or 3 times per week tended to
give better control of anthracnose than Bravo at 2 or 2.5
pts/A applied twice per week or Captan applied 2 or 3 times
per week but there were no statistical differences in control
among the treatments.
c. Bravo applied twice per week at rates of 1.5 pts, 2 pts, or
2.5 pts per acre caused slight phytotoxicity after 11
applications. Bravo applied three times per week at 1.5
pts/A caused phytotoxicity after 16 applications.
Phytotoxicity in all the Bravo plots occurred at the same
time in mid August and did not increase with subsequent
4. The following treatments were compared for control of gray mold of
strawberries: Captan, Bravo, Ronilan, Tersan SP, Aliette, and
Rovral each applied alone twice per week all season, and Captan
applied twice per week until gray mold occurred in late Feb., then
Captan applied each week on Friday and Ronilan, Rovral, or Aliette
applied on Tuesday each week for the remainder of the season. The
treatment of Captan until gray mold occurred followed by Captan
and Ronilan each week gave the highest marketable yield but this
was not statistically greater than marketable yields from several
of the other treatments.
5. The following treatments were compared for control of fruit
anthracnose; 1) Bravo twice/wk until harvest began followed by
Captan twice/wk for the remainder of the season, 2) Captan
twice/wk, 3) Bravo twice/wk, 4) Tersan SP on Tuesday and Captan on
Friday each week. 5) Tersan SP 2 Ibs/A twice/wk, and 6) Tersan SP
1 Ib/A once/wk. Treatments 1 and 2 gave the highest yields of
marketable fruit. Treatments 1 through 4 gave significatnly
better control of anthracnose on fruit and flowers than treatments
5 and 6.
1. Determined that when healthy strawberry plants are set in pots in
contact with crowns infected with Colletotrichum fragariae and
Glomerella cingulata, the fungi that cause anthracnose crown rot,
the healthy crowns do not become infected.
2. Determined that none of 10 isolates of C. acutatum killed plants
when injected into the crowns.
3. Determined that when crowns of potted plants are injected with
spores of C. fragariae or G. cingulata, neither species spreads to
noninjected-plants 2 inches-distant, that C. fragariae did not
spread to noninoculated crowns touching injected crowns, but that
there was some spread of G. cingulata to noninoculated crowns
touching injected crowns.
4. For the first time in Florida a strawberry field was discovered in
which it appeared that crown infection by a Colletotrichum species
(probably fragariae) occurred after plants were set in the
fruiting field. Colletotrichum was isolated from wild grapes
growing at the end of the field where severe infection occurred.
The isolates will be tested for pathogenicity to strawberry.
5. Isolated Phytophthora cactorum, the cause of vascular collapse
disease, from dying strawberry plants for the first time in
6. It was determined that for control of fruit anthracnose of Pajaro,
and for control of graymold and fruit anthracnose of Chandler,
treatments of Captan twice per week or Bravo twice per week until
fruiting began followed by Captan twice per week for the remainder
of the season resulted in higher marketable yields of both
cultivars than Captan once per week or Thiram or Bravo twice per
week all season.
B. Entomology J. F. Price and Marinus Van De Vrie
1. Performed experiments to determine the impact of the newly
introduced Asian cockroach on strawberry fruit. Found this insect
to be a potential threat to production.
2. Performed experiments to find registered and not-yet-registered
miticides useful to manage spider mites infesting strawberries.
3. Developed new IFAS recommendations on managing arthropods in
strawberry crops based on newly developed information and changes
in alternatives available to the industry.
4. Developed and provided current research data to the Florida
strawberry industry, FDACS and EPA to provide a basis for the new
registration of abamectin (bacterial fermentation product) to
provide relief for an emergency spider mite problem.
1. A comparison was made of Phytoseiulus persimilis (available from
commercial insectaries) and Phytoseiulus macropilis (naturally
occurring in Florida) predatory mites for control of twospotted
spider mite. Both of these species provided good control.
2. One, two and three releases of the above predators were compared
for effectiveness of control for the twospotted spider mite.
There was no additional advantage to performing multiple releases.
3. It was determined that adults of the Phytosiulus persimilis
predator of twospotted spider mite can disperse at least 75 feet
from points of release during one week.
4. The longevity and reproduction of and host effects of the
twospotted spider mite were compared on eight strawberry
cultivars. No difference in spider mite reproduction or longevity
was found, but 'Selva' leaf quality decreased rapidly with spider
C. Nematology A. J. Overman
1. Micro-irrigation: Procedures have been developed for controlling
soil pests in established full-bed mulch culture using micro-
irrigation systems for injecting nematicides, soil fumigants, or
bio-control agents. Vapam is now commercially used in
microsystems to prepare beds for double-cropping. Methyl bromide
is promising as a hot gas applied via the drip tube for double
cropping when the tube is buried at least 3 inches mid-bed and the
plastic mulch is intact over at least 95% of the bed surface.
2. Liquid Wheel: Where microsystems are not in use, a liquid
injection wheel has been used to sidedress nematode infested crops
with liquid nematicides or with a soil fumigant to kill the
initial crop in preparation for a double crop.
D. Weed Science J. P. Gilreath
1. Post-emergence control of broadleaf weeds in strawberry can
usually be obtained legally with Enquik and Paraquat.
2. Field trials were run to develop supportive data for registration
of Poast and Fusilade through the IR-4 program.
III. PRODUCTION, CULTURE MANAGEMENT AND ENVIRONMENTAL STRESS E. E. Albregts
1. Containerized strawberry transplants were produced which held root
balls together and required little irrigation to establish in the
2. It was shown that California developed strawberry cultivars give
little to no response to K fertilization when grown on previously
cropped land, whereas Florida developed cultivars respond to
moderate K fertilization.
3. Three slow release nitrogen fertilizer sources were evaluated
under two irrigation systems. Under microirrigation, total fruit
yields were not different because of nitrogen source (IBDU, sulfur
coated urea, and osmocote). With overhead sprinkler irrigation
total yields from IBDU were lower than those from the other 2
sources. With overhead irrigation, maximum total yields occurred
at 200 Ibs nitrogen/acre, but with microirrigation, maximum yields
occurred at 180 Ibs nitrogen/acre.
4. Calcium nitrate at 4.4 and 8.8 Ibs/acre and calcium chloride at 3
and 6 Ibs/acre were applied biweekly to fruiting strawberry as a
foliar spray. The higher calcium rates reduced marketable fruit
yields compared to the control treatment receiving only water.
Slightly more light colored fruit were produced by the calcium
chloride treatment than with the control. Average fruit weight
was not affected by treatments.
1. Four slow release nitrogen fertilizer sources were evaluated,
under 2 irrigation systems. Under overhead irrigation, fruit
yields were not affected by nitrogen source. With drip irrigation
one of two clones had reduced yields with the sulfur coated urea
2. Field studies demonstrated that preplant fertilizer was not needed
for drip irrigated strawberry if fertilization through the
irrigation system is started within 5 to 10 days of transplanting.
(Cooperators-Dr. Gary Clark and Dr. Craig Stanley).
3. Potassium sources from potassium chloride, sulfur coated potassium
sulfate, or osmocote potassium sulfate were applied at 0 to 200
Ibs/acre to 3 strawberry clones for 2 seasons. Potassium sources
had no consistent affect on yield, and did not affect average
fruit weight. Optimum K rate was between 90 and 140 Ibs/acre.
The most persistent K source in the soil was osmocote.
4. During the Christmas freeze of 1989, the air temperature was below
freezing for 30 hours with a minimum of 22 degrees. Row covers (9
oz/yd) with overhead sprinkler irrigation (on at 28 degrees F)
gave good flower and fruit protection. Irrigation alone gave
fruit and flower losses of about 10% while row covers alone had
losses similar to plants receiving no protection, which was from
70 to 90% loss.
5. Early yield and occasionally the total fruit yield of California
developed strawberry cultivars were reduced when grown in Canadian
nurseries if foliage was removed either two weeks prior to harvest
from the nursery, at harvest, or just prior to planting.
IV. WATER MANAGEMENT AND NATURAL RESOURCE PROTECTION FOR STRAWBERRY WATER
PROGRAM G. A. Clark, E. E. Albregts, C. D. Stanley, A. G. Smajstrla, and
F. S. Zazueta
1. A completed 3-year project evaluating the use of tailwater
recovery systems for strawberry production showed more than a 60% j
reduction in deep well pumpage resulted with the system. A
computer software package was developed to simulate pond behavior
as affected by different management practices and to aid in pond
1. The second season of a three season field study of water and
fertilizer management on drip irrigated strawberries was
completed. To help schedule daily irrigation events, water
management tensiometers were used. Tensiometer thresholds of 10
to 15 cb resulted in a seasonal drip irrigation application of
about 7 inches as compared to an application of 11 inches for the
5 cb management threshold. Water management treatment did not
affect yield or quality of fruit. These results were consistent
with the 1988-89 season. The third production season of the study
was initiated in October, 1990.
2. The second season of a three season study of water requirements
and crop coefficients of strawberries was completed using the
lysimeter facility at the AREC-Dover. The 1989-90 season
evaporative demand and growth water requirements averaged 10
inches. Crop coefficients average 0.05 during Nov. and Dec.,
increased to 0.50 during Jan. and Feb., and peaked at 0.94 during
March and April. The third crop study was initiated in Oct. 1990.
The information contained in this report is a summary of experimental results
and should not be usd as recommendations for crop production. Where trade names
are used, no discrimination is intended and no endorsement is implied.
The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University