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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
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Grape Field Day
Agricultural Reonarch Center
UniversIty of l'lorlda, V'AS
Thursday, August 21, 1980
9:30 a.m. to Noon
J. A. Mortensen
Dr. Tim Crocker, IFAS Deciduous Fruits Extension Specialist,
Program in Barn Breezevay
9:30 10:05 AM. Registration and muscadire fresh fruit taste
panel. All persons in attendance are Invited to rate varie-
ties for quality. Also, a separate table with juices or
other processed grape products will be available.
10:05 AM. Welcome by Dr. Gary Elmstrom, Center Director, ARC,
10:10 10:50 AM. Discussion of grape research in progress. Ques-
tions during all the discussion;, are welcome.
Dr. D. L. Hopkins, Plant Pathologist, Leesburg
Dr. W. C. Adlerz, Entomologist, Leesburg
Dr. C. P. Andrews, Assoc. Horticulturist, Monticello
Dr. R. P. Bates, Food Scientist, Gainesville
Dr. J. A. Mortensen, Geneticist, Leesburg
Guided Tour of Vineyard
10:50 AM. Guided tour of experimental grape vineyard. Included
on the tour will be a mist propagation unit, new well, pump,
and vineyard irrigation system, effect of ethephon on ease
of harvesting, a view of varieties and new selections of
muscadine grapes, and a chance to pick fruit in designated
rows for carry-home at the conclusion of the tour. Pick- -
only in designated areas'for carry-home!
roon. End of field day.
,* ( o
Leesburg ARC Research Report (WG 80-3) n
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Insect Control on Florida Bunch Grapea (W. C. Adlerz)
:lany insects can be found on Florida bunch grapes. Some can be
severely damaging if they occur in large numbers and control may
tib necessary. To keep spraying to a minimum, growers may wish
to become acquainted with insects having the greatest damage
poccntial, inspect vines frequently, and spray only when necessary.
Partial List of Florida Grape Insects
Class la Class 2a
Grape flea beetle Grapevine aphid
Grape leaf skeletonizer Sharpshooters
Seed chalcid Scale insects
Grape leafhopper Grape leaf folder (Class 1-2)
Grape root borer Achemon sphinx large caterpillars
Scarab beetles (Anomala, class 1-2).
Fruit beetles, bees, and wasps
a Class 1 insects have a greater damage potential than Class 2
Grape Flea Beetle
Damage by grape flea.beetles results mostly from adult feeding
on newly emerging buds in the spring, and adult and larval
feeding in the flowers. Spray when necessary.
Grape leafhoppers breed on grape plants. Adult and young leaf-
hoppers feed on the undersides of leaves, removing chlorophyll
and leaving pale feeding spots. Feeding spots may be so numerous
as to cause yellowed leaves and leaf drop. Excreta from these
Insects may collect on the fruit which will then be spotted and
p:si3bly covered with sooty mold. An application of insecticide
made prior to flowering and a second application two weeks later
will kill many overwintering adults and reduce the spraying
needed later in the year when the plants are larger. To keep
plants as vigorous as possible, grape leafhoppers should be
Seed chalcids will affect the following bunch grapes that are
adapted to Florida growing conditions: Blue Lake, Lake Emerald,
Stover, and Norris. It appears that Blue Lake is the most
susceptible variety. No information is available on susceptibility
of SV 12309. Where experience shows that seed chalcids are
abundant, an annual preventive spray program will be necessary.
Wasps about 1/8" long arrive, at grapes in lat6 April and continue
activity through May. Eggs are laid in the developing seed during
this period. Wasps complete their development to adult within
the need. Adults bore out through seeds, pulp, and skin just
before grapes ripdn, thereby ruining any infested grapes.
Complete crop loss is possible.
Malathion once weekly from the last of April through May (5
applications) gave good control experimentally in a location
where seed chalcids were damaging. Preventive spraying is
recommended because the wasps are hard to detect visually during
the egg laying period.
Grape Root Borer
The grape root borer is the larval form of a wasp-like moth.
Larvae tunnel into the larger roots and crcwn below the surface
of the soil. Vines show a general decline in vigor and may be
killed. Life history and control methods have not been worked
out in Florida. Control is usually considered difficult.
Insecticides For Grape Insects
Amount per Days before Insects
Spay material gallon harvest1 controlled
Malathion 50-57% EC2 1 1/2 t4 3 Malathion
Malathion 25% WP3 4 T 3 aphids
Sevin 50% WP 2 T 0 scale insects
Sevin 80% WP 4 t 0 Sevin
Sevin 23-25% flowable 4 t 0 leafhoppers
Malathion or Sevin
1 Minimum number of days between last application of the pesticide
2 EC = emulsifiable concentrate.
3'WP = wettable powder.
t = teaspoon, T = tablespoon.
1977 Leafhopper Control Test (W. C. Adlerz)
Purpose: Comparison of times and frequencies of Sevin application
to control grape leafhoppers.
Procedure: Treatments were applied to 4-plant plots replicated
5"times. The treatment schedule is listed in the table below.
Treatments were applied in 100 gallons of water per acre using
a Solo Mistblower Model 410.
Preliminary Results June 11,'
Treatments Rate/acre Loafhoppers/10 leaves
oevin, pro-bloom + 1 month 1.0 1.67
Orthene, post bloom 0.5 1.67
Sevin, post-bloom + 1 month 1.0 3.50
Sevin, pre-bloom 1.0 6.00
Sevin, post-bloom 1.0 6.33
No treatment 14.17
Evaluated 70 days after pre-bloom and 50 days after post bloom
Results 1976: Orthene and two new synthetic pyrethroid materials
gave excellent control of grape leafhoppers, but the effects of
Orthene were more persistent.
1976 Thrips Control Test: A synthetic pyrethroid material,
FMC 33297, gave excellent control of thrips. Guthion and
Orthene were very good and somewhat better than Cygon.
In a second test, Lannate was more effective than Diazinon,
Guthion, and Malathion. Guthion and Malathion gave good control.
Disease Control of Bunch Grape in Florida (D. L. Hopkins)
Disease control is an absolute necessity to successful bunch grape
production in Florida. The most severe fungal disease is an-
thracnose, which affects both foliage and fruit. There are 3
other fungal fruit rots black rot, ripe rot, and bitter rot -
that must be controlled. A number of leafspot diseases become
serious problems during late summer. These diseases must be
controlled to prevent premature defoliation in the fall, thus
assuring a stronger vine in dormancy and better yields the
A long growing season, high temperatures, abundant rainfall,-and
high humidity make grape diseases very difficult to control in
Florida. Therefore, a vigorous spray program must be started in
the spring when buds are 2-6 inches long and continued throughout
the season. Fungicides should be applied every 10-14 days until
a week before harvest, and every 3-4 weeks from harvest through
November or until dormancy.
The fungicides Manzate D, Dithane M-22 SpeptaIl, Captan, Phaltan,
and Benlate are effective in controlling grape diseases in
Florida. In recent tests, Denlate and Capt-an haV'e been especially
effective in controlling black rot, thus increasing marketable
yields. A spreader-sticker may be included in the spray. A
winter spray of lime sulfur, 2 qts. of 26-31% solution per 100
gallons of water (1 1/4 tablespoons/gal) is suggested for
Fungicide per acre gal. harvest
Manzate D 1 1/2 lb. 1 1/2 TBS2 7
Dithane M-22 Special 1 1/2 lb. 1 1/2 TBS 7
Captan 2 lb. 2 TBS 0
Phaltan 2 lb. 2 TBS 0
Benlatp 1-1 1/2 lb. 1-1 1/2 TBS 7
1 This is the recommended minimum number of days between last
application of fungicide and harvest.
2 TBS = tablespoon.
1977 Fungicide Test
Purpose: To evaluate various dormant sprays for the control of
grape foliar diseases.
Procedure: The trial area consists of 5 rows of 'F4-36' with
20-25 plants per row. Treatments were applied on February 28
in 100 gallons of water using a Solo Mistblower Model 410. The
dormant sprays were applied to thoroughly wet all wood.
Beginning March 24, Benlate at 1.0 lb/100 gal has been applied
at approximately 3-week intervals to the entire test area.
Tribasic Copper Sulfate
canes 0-5 rating
* Not registered for use on grapes.
Pierce's Disease Control (D. L. Hopkins)
Pierce's disease is the principal factor limiting the production
of grapes in Florida. The disease was long thought to be caused
by a virus but has been shown in recent years to be caused by a
small bacterium resembling a rickettsia. Whereas the only current
control of Pierce's disease is resistance, the discovery that the
causal agent is a bacterium increases the prospects for chemical
control of the disease with antibiotics.
Antibiotic tests on 'Schuyler' grapevines: On untreated 'Schuyler'
grapevines symptoms of Pierce's disease developed on 40% of the
vines in the second season, and by the fourth year all of the vines
had the disease. Weekly sprays of 500 ppm oxytetracycline delayed
Pierce's disease development until the third year. Symptoms
remained mild in this treatment throughout the four-year test as
only 8% of these vines died. A monthly 500 ppm drench treatment
delayed symptom development only 6 months. Biweekly sprays of
1000 ppm also only delayed symptoms for 6 months, but when changed
to weekly sprays 1000 ppm oxytetracycline seemed to stop further
disease development completely.
In summary foliar sprays of antibiotics appear to be more effective
than drenches. With foliar sprays, concentrations of at least
500 ppm were needed, and weekly application was best. More work is
needed on rates and timing of antibiotic sprays before any practical
control of Pierce's disease is possible.
Weed Control in Florida Vineyards (J. A. Mortensen)
One of the secrets of successful grape growing is an integrated
program of weed control involving mechanical tools, herbicides
and mulches. Weed control between vine rows is much easier to
accomplish than that under the trellis itself. Herbicides are
rarely used for weed control between rows since disking, rototilling
or mowing are more practical and less expensive both in young vine-
yards and mature vineyards. The discussion below concerns control
of weeds in the vine row where disking and mowing arc nrot nossible.
Young vineyards. Mulching with 2 to 3 inches of oak leaves
around each newly set grapevine helps control weeds and conserve
soil moisture. Hoeing of weeds in small vineyards is usually
replaced by Paraquat spraying or in-and-out rototilling, or both,
in vineyards one acre or larger. Paraquat kills all the loaf
surface it covers, including grapevine foliage. A tractor-
mounted boom with a nozzle surrounded by a cone-shaped shield
to prevent drift of spray in windy weather is effective in
directing the material to a band along each side of the row
without getting on the grape plants. Sufficient overlap of spray
bands between vines in the row is essential to avoid leaving a
green strip of weeds under the trellis wire. The in-and-out vine-
yard rototiller (Hester Plow Company, Lake City) is mounted on the
side of the tractor and operates from the power take-off. It is
very effective in controlling both broadleaf and grassy weeds in
the vine row. Dalapon herbicide controls grassy weeds. Apply in
April or May, or when the grass is green and actively growing.
Avoid spraying the grapevine foliage or on bare ground.
Mature vineyards (3 years or older). Karmex (Diuron) herbicide
is an effective pre-emergence herbicide if applied once a year,
usually in March. Weed growth occurring in the rows in mid- to
late summer can be burned down with Paraquat herbicide, hoed, or
In-and-out rototillod. Dalapon is effective on grassy weeds such
as Bermuda grass sod. Do not mix Dalapon with other herbicides
in the spray tank. Karmex and Paraquat may be mixed where both
a pre-emergence and "burn-down" of existing weeds are needed at
once. Thorough cleaning of spray tank, hose, and nozzles by
draining, flushing, and cleaning with detergent are recommended
following the use of herbicides. Roundup (Glyphosate) has'also
given excellent control of weeds but is not cleared for use on
bearing grapevines yet.
Herbicides.u~ed for grapes .
1 qt./50 gal.
5 lbs./50 gal.
100 sq. ft.
Amt. of X-77
4 oz./50 gal.
Wet above-ground portion
of weeds whenever needed
(3 to 5 times a year)
Wet leaf surface when
grass is actively growinB
(twice each year, 3
Wet surface of ground
evenly in a band on eacn
side of row (once each
year, usually March).
Vines must be 3 yrs. oldi
and 1 1/2 inches trunk
1 Caution: muscadine grapes are subject to injury by Dalapon if
the ground is bare and the material is taken up by the vinu roots.j
Irrigation of Grapes (J. A. Mortensen)
Research on irrigation of grapes in Florida has been needed for
some time in order to determine whether the improvement in vine
growth, yield, and quality is sufficient to justify the cost of
irrigating. Beginning in June 1976 we now have a one-acre
irrigation trial on muscadine grapes and a half-acre trial on
bunch grapes. The treatments are (1) Microjet irrigation plots
and (2) Non-irrigated check plots. No data are available at
this time, but the Microjet system will be demonstrated during
the vineyard tour. A marked response to irrigation in shoot
growth and yield is evident in 1977. All irrigation equipment,
including the filter, was donated by the Southern Citrus Nurseries
Corporation, Dundee, Florida, who sell Microjet systems.
*Fortilizer N-P--K Factorial Experiment (J. A. Mortensen)
A ratio of 3:1:2 or 3:1:41 was apparently superior to the 1:1:1
ratio of N:P:K presently recommended for grapes. However, ---..
differences were not statistically significant for yields or
weight of dormant pruninr. wood. Under conditions of no
irrigation, Growth and yield of Blue Lake and Norris bunch
grapes were greater where clay was 2.5 to 4 ft below surface
than where it was 5 or more feet deep.
Marketing Florida Bunch Grapes as Fresh Fruit (L. H. Stover)
Tests of marketing Florida bunch grapes through central Florida
retail outlets were conducted in 1973, 1975 and 1976. The
predominant variety in these tests has been Stover (light green
to golden color), but limited amounts of blue- and red-skinned
grapes have also been sold. Grapes have been marketed through
one large retail chain (Pantry Pride) and through several smaller
local stores. Retail price has ranged from 39 to 49 cents per
pound in packaged cartons of about one pound. Grapes were
marketed over a period of 3 weeks, usually prior to the
availability of full-ripe Thompson Seedless grapes from Arizona
and California. Grapes were sold to the stores at 31 cents per
pound in 15-pound cartons. The stores were pleased to get the
grapes as offered and had good success in selling them. Blue
and red grapes appeared to be more popular than golden ones.
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