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II Volume 11, Isue
Resistance of UF strawberry cultivars to Botrytis
and anthracnose fruit rot
Craig Chandler and Jim Mertely
Two field trials were conducted last season to
evaluate the new UF/IFAS strawberry cultivars
'Earlibrite', 'Strawberry Festival', and 'Carmine' (FL 95-
256) for resistance to Botrytis fruit rot (gray mold), caused
by Botrytis cinerea, and anthracnose fruit rot (black spot),
caused by Colletotrichum acutatum. 'Sweet Charlie' was
included in these trials as a standard (we know from past
experience that 'Sweet Charlie' is very susceptible to
Botrytis fruit rot, and resistant to anthracnose fruit rot).
Fungicide spray programs were adjusted to allow Botrytis
fruit rot to develop in one trial and anthracnose fruit rot in
the other. Fruit were harvested and evaluated over a four-
week interval (Botrytis trial) or a five-week interval
anthracnosee trial), beginning on February 19, 2002.
'Strawberry Festival' and 'Carmine' were less
susceptible to Botrytis fruit rot than 'Sweet Charlie', while
'Earlibrite' was comparable to 'Sweet Charlie' in
susceptibility to this disease (Table 1). With respect to
anthracnose fruit rot, 'Strawberry Festival' was very
susceptible while 'Earlibrite' and 'Carmine' appear to be
moderately resistant (Table 1). Additional field trials will
be conducted during the 2002-03 season to confirm these
Table 1. Percentage of strawberry fruit harvested from 19
February to 15 March that expressed symptoms of Botrytis or
anthracnose fruit rot.
Cultivar incidence (%) incidence (%)
Sweet Charlie 18.7 bz 2.4 a
Earlibrite 17.0 b 13.6 b
S. Festival 9.1 a 28.9 c
Carmine 7.2 a 9.6 b
zPercentages within columns followed by different letters are
Pre-plant treatments for control of Colletotrichum
acutatum and enhancement of strawberry
Kirk D. Larson and Douglas V. Shaw, UC Davis
In the 2002 production season, significant losses
and production delays occurred in fruit production fields
due to use of planting stock infected with Colletotrichum
acutatum. However, because the pathogen may be
present at low levels and infected plants are often
asymptomatic in the nursery, identifying infected planting
stock is difficult.
Colletotrichum acutatum root and fruit rot
We conducted a field study to determine the
effectiveness of pre-plant wash/dip treatments in
suppressing C. acutatum and enhancing vegetative growth
of bare-root 'Camarosa' transplants from commercial
California high-elevation nurseries in mid-October, 2001.
High-elevation plants were field-run commercial
transplants destined for use as planting stock in fruit
production fields this past fall. Plants were trimmed to
California commercial standards (i.e. the leaves were
removed), cooled and transported to Irvine, treated and
planted in replicate plots of 12 plants each on October 23.
The four treatments were: 1) non-treated control; 2) wash
in water to remove all soil; 3) water wash followed by a
15-minute immersion in Quadris (14.2 fl oz/100 gals
water); 4) water wash followed by a 15-minute immersion
in Switch (11.0 fl oz/100 gals water). After planting,
flowers of all plants were continuously removed to
encourage vegetative growth and prevent confounding
effects of fruit load between treatments. At periodic
intervals, vegetative growth was assessed for all plants by
measuring canopy diameters. Overall, plants treated with
Wash+Quadris had greater growth than Control plants;
plants subjected to Wash alone also had improved growth
compared to Control plants (Table 2). SwitchR was
ineffective in promoting growth at the rate used, and
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actually may have been phytotoxic. However, recent dip
trials using Switch at lower rates appear effective for
control ofC. acutatum in strawberry.
C. acutatum was not detected in 'Camarosa'
plants prior to planting. Presumably, growth responses due
to use of Wash or Wash+Quadris treatment resulted from
suppression of C. acutatum, which may have been present
at undetectable, but harmful, levels in much of the
experimental plant material. Treatments also may have
controlled other harmful pathogens, or growth responses
may have been due to beneficial root hydration.
Additional pre-plant dip studies are needed.
Table 2. Vegetative growth of high elevation Camarosa
transplants treated with four different wash/dip treatments
Treatment Plant diameter. (cm)
Water wash + Quadris y 19.56 a
Water wash 16.98 b
Control (no wash) 14.30 c
Water wash + Switch z 14.25 c
Y 15 min dip in Quardis @ 14.2 oz/100 gal
z 15 min dip in Switch @ 11 oz/100 gal
Note: Switch and Quadris are NOT currently labeled
for use as a pre-plant dip in strawberry. Also, while
washing transplants may reduce incidence of certain
pathogens and enhance transplant growth, this same
treatment may spreadXanthomonasfragariae (angular leaf
spot) and other harmful pathogens.
Update on use of Quadris as a pre-plant dip for
the control of plant establishment problems
caused by Colletotrichum acutatum
We have heard that anthracnose has been
observed in some nurseries this season. Hopefully this
will not result in major problems like last season when
many growers in Florida and California had plant
establishment / root rot problems caused by Colletotrichum
acutatum in early season transplants. In Florida, these
problems were most common on plants set before October
15th. This was probably due to the greater stress and
slower establishment that transplants experience when they
are set before mid- October due to the warmer weather and
the lack of chilling in the nursery. Therefore, we
recommend that growers consider not planting cultivars
that are susceptible to anthracnose root rot, such as
'Camarosa', before October 15.
The FSGA, FFVA and Syngenta are currently
working to get a label for pre-plant dipping of
strawberry plants in Quadris u. Currently, Syngenta has
requested a supplemental Federal label for Quadris
that will include pre-plant dip applications.
Unfortunately, it looks like it will be late October or
early November before Federal approval is obtained.
Syngenta considers pre-plant dipping the best way to
use Quadris for the control of root rot caused by C.
acutatum and is not pursing a label for application
through drip tape. It is unlikely that drip applications
are effective due the large volumes of water used and
the difficulty of getting material into the root zone.
There are also concerns about the development of
resistance to Quadris in the pathogen when it is
applied through drip lines.
Plants stunted by
This is a draft of the proposed supplemental
Quadris dip label:
Products: QUADRISTM Fungicide
EPA Reg. No. 10182-415
Use: For suppression of root and crown rot
caused by Colletotrichum spp. in strawberry plants
intended for commercial strawberry fruit production.
Directions for Use
It is violation of federal law to use this product
in a manner inconsistent with its labeling.
Apply as a pre-plant dip to strawberry roots
and crowns at the rate of 5 to 8 fluid ounces per 100
gallons of water. Completely immerse planting stock in
solution. DO NOT reuse water solution. It is
recommended that transplants be washed to remove
excess soil prior to dipping. Dip or expose plants for a
minimum of 2 to 5 minutes. Dispose of dip solution
according to local restrictions.
Plant treated plants as quickly as possible. For
continued anthracnose control, follow with foliar
applications of Quadris or other labeled fungicide
beginning 2-3 weeks after transplant.
Do not use in strawberry nurseries, or on
plants intended for use in strawberry plant propagation,
lathe houses, greenhouses, or other nursery setting.
Do not mix Quadris with other pesticides in
Quadris is not currently labeled for use as
a pre-plant dip application.
The use of trade 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 exclus-on of others of stable
composition Usepesticidessafely Readandfollowdirectionsonthemanufacturers
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Spotlight on Diagnosis: The proper procedure
for collecting plant samples for examination by
the GCREC-Dover disease diagnostic lab
Jim Mertely and Dan Legard
Within the next several weeks, strawberry
plants will be in the field, and we hope the
establishment process goes well. If something goes
wrong, and the transplants grow poorly or begin to die,
the UF Strawberry Disease Clinic is available to help
diagnose the problem. It is important to collect a good
sample to help us provide an accurate diagnosis. A
good sample typically consists of 5 to 10 plants which
are still green, but representative of the problem in the
field. Dead plants are already colonized by decay
organisms, which outgrow the disease organisms and so
they do not make useful samples. Be sure to dig, rather
than pull up the plants. Root-rotting fungi such as
Colletotrichum acutatum, Clyindrocladium,
Phytophthora, Pythium, and Rhizoctonia can be
responsible for many establishment problems. The
more complete the root system is, the better the chances
of finding out which of these fungi are involved, and
what might be done to help the crop. Shake off excess
soil from the roots and place the plants in a plastic bag,
then place the sample in a cooler (if available). Do not
add excess water to the bags, or expose the plants to
excessive heat or sun.
include 5 to 10
Bring the sample to GCREC-Dover as soon as
possible. We prefer that samples arrive between 9 and
12 in the morning. Be prepared to fill out a form that
asks about the strawberry variety, planting date,
agrochemicals used, etc. Your personal observations
concerning pattern of disease in the field and what you
think might be wrong are also very helpful. For this
reason, the grower or someone familiar with the
problem should bring in the sample. After we receive
the sample, be prepared to wait 4-6 days for a
diagnosis. This allows us time to isolate and identify
the disease organisms. Usually we will respond by
phone, though it may be necessary to return to the lab
to pick up a fact sheet describing the disease and how to
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) 744-6630 SC512-1160
Website http//strawberry ifas ufl edu
Editors Dan Legard (leardi)uLfl edu) & Craig Chandler (ckc~ @ .ufl d),
Design, Layout& Distribution Christine Manley (cmanlevy ufl edu),
Director Jack Rechcial
Implement spider mite management plan now
James F. Price
The first arthropod pest we experience each
season is the twospotted spider mite and plans for
managing it must be made before the season begins.
The steps in developing a management plan include
ordering high-quality transplants as free of spider mites
as possible, assessing the pest status of the plants as
they arrive, and scouting and deciding the scheme of
remediation when spider mites become problematic.
The last two steps are important this time of the season
and will be discussed below.
infestation with 5X
As plant shipments arrive, boxes of transplants
should be selected for inspection that represent each
production site, as far as that can be determined, and
variety within that shipment. The lower surface of all
the leaves of one transplant per bundle within a selected
box should be examined with a 5X hand lens. Records
should be made of the number of transplants on which
spider mites or their eggs are found. The number of
boxes examined determines, to a large extent, the
reliability of the estimate of spider mite infestation. If
more than 1% of the transplants carry spider mites, then
growers can expect a quick emergence of spider mite
problems after the transplants are established.
There are two schemes for spider mite
remediation available in the fruiting field, biological
control with predatory mites and chemical control with
miticides. Contacts with reliable producers of predators
must be made early if the biological control option is
exercised and predators should be released at one per
transplant as soon as 5%-8% of sampled leaflets
possess a spider mite or egg, but not before the
strawberry plants have four fully expanded new leaves.
If mites exceed the treatment levels before the plants
have grown sufficiently, then one of the miticides
mentioned below can be applied to control mites
temporarily and allow for the necessary growth.
Miticidal control has become more reliable
than in the past. This is because of the availability of
Savey and Acramite in addition to Agri-Mek and
V inilc Producers of Savey advocate early use of
their product once more than 2% of transplant leaflets
possess one or more spider mites or eggs. Since
Savey is an ovicide/larvacide it is necessary to apply
an adulticidal miticide such as Agri-Mek or \~V n le.
along with it. Manufactures usually suggest that the
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other miticides also be applied when mite populations are low, or when about 5% of the samples leaflets are infested. Careful
planning in the use of miticides based on scouting is very important because seasonal applications are limited to one of Savey,
two of Acramite or V, n.c and four of Agri-Mek.
Big disasters can occur if spider mites are not detected in a timely fashion and appropriate action taken. Early
planning and scouting can avoid the loss.
Intermittent sprinkler irrigation for establishment
The application of overhead (sprinkler) irrigation is necessary to minimize desiccation and mortality of strawberry
transplants due to their limited and damaged root system and high temperatures on black plastic mulched beds in Florida With
the advent of computer controlled irrigation systems, it is now possible to apply sprinkler irrigation intermittently to minimize
the amount of water needed for establishment. Research that was done by Drs. Albregts and Howard in the 1980's on the
optimization of intermittent irrigation for establishment showed that pulsing overhead irrigation in on/off cycles for 5/15, 10/20,
5/10 and 15/15 minutes did not reduce strawberry yields as compared to continuous irrigation during the establishment period.
Through the use of computerized control systems, water usage for establishment of strawberry can be cut by up to 75%.
Humidity and wind speed need to be taken into account when determining on/off cycle durations. For example under high
wind conditions, a 5/10 minute on/off cycle should be used instead of a 10/20. While the amount of water used is the same, the
length of time when plants can become dry and bed temperature increases are reduced. The use of intermittent overhead
irrigation during establishment not only saves water but can reduce pumping costs, keep water use below permitted amounts,
and reduce leaching of fertilizer in the bed.
Drip irrigation school
John R. Duval
Do you want to make the most efficient use of your water, fertilizer, and chemical resources? Then come to the Drip
Irrigation School taking place on November 13 from 10 AM to 4 PM at the GCREC-Dover and find out how. Topics to
be covered include injection of fertilizers and chemicals, irrigation scheduling, drip system trouble shooting, soil water
monitoring, and irrigation BMPs. Lunch will be provided and CEU and CCA credits will be available. If you are interested in
attending please call Christine Manley at 813-744-6630 ext 60 or e-mail her at email@example.com.
We would like to express our appreciation to 3 Star Farm, Strawberry Ranch, and Sydney Farm for providing the
equipment and labor to fumigate and bed our field for the upcoming season; to Hendrix and Dail, Inc. for supplying the
fumigant; to ProSource One and Pliant Corp. for supplying the plastic mulch; to James Irrigation, Inc. for supplying the drip
tape; and to Gro-Mor Company for supplying the pre-plant fertilizer. Through the combined efforts of the local industry and
growers, we are able to continue our research and provide the strawberry industry with up-to-date recommendations to improve
the productivity of the industry.