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Copyright 2005, Board of Trustees, University
1 7- I
SUGGESTIONS FOR THM CONTROL OF DISEASES AND INSECTS
OF HYDROPONIC TOMATOES
R* S. Cox and N. C. Hayslip
The production of hydroponic tomatoes has become an
important industry in south Florida. This report is
in recognition of the uniqueness and of the intensive
nature of their disease and insect problems. It in-
corporates, where applicable, control practices used
for soil-grown tomatoes and discusses control proce-
dures for problems peculiar to the hydroponic industry.
INDIAN RIVER FIELD LABORATORY MI EPORT 7-1
INDIAN RIVER FIELD IABORATOR.1IM30 REPORT 57-1 \
Ft. Pierce, Florida
August 15, 1956
SUGGESTIONS FOR THE CONTROL OF DISEASES AND INSECTS
OF HYDROPONIC TOMATOES
R. S. Cox and N. C. Hayslip
The growing of hydroponic tomatoes has emerged as a permanent industry in
sputh Florida. Due to its intensiveness, the acreage involved does not provide a
true yardstick of its economic importance. It also follows that disease and insect
problems are multiplied because of the intensified cultural practices employed by
the growers. For example, southern bacterial wilt is sporadic on field-grown toma-
toes in south Florida; whereas, in the case of hydroponics, successful growers must
treat routinely for this disease. This report is the outgrowth of numerous requests
by the growers for information on disease and insect control.
At the present time the variety, Manalucie, is recommended for use in hy-
droponics. It produces large, firm tomatoes which are slow ripening and somewhat
resistant to cracking. Another desirable feature of this variety is its resistance
to several diseases. This simplifies considerably the disease control program.
The recommended variety, Manalucie, is highly resistant to gray leaf spot
and Fusarium wilt. It also carries moderate resistance to early blight and is a
symptomless carrier of tobacco mosaic. Still, there are at least four important di-
seases with which the successful grower must learn to cope. These are listed in
Table 1, below, with the effective chemicals for their control appearing in the
Table *1 Common diseases of hydroponic tomatoes and effective materials for
The Disease Effective Material
1. Southern bacterial wilt Formaldehyde
2. Bacterial spot Agri-strep, Agrimycin 100, Phytomycin, Tri-
basic Copper sulfate, Copper A, Bichloride
3. Late blight Parzate, Dithane Z-78, Manzate, Dithane M-22,
.. Botrytis gray mold Phygon, Fermate
The bacterium that causes southern bacterial wilt is soil borne. It in-
vades the water-conducting elements (tubes) of the plant and clogs them, thereby pro-
ducing wilt. The bacteria escape from diseased roots into the nutrient solution and,
in turn, attack the roots of healthy plants. It is readily seen that under favorable
conditions all the plants supplied by a common source of liquid nutrients soon become
diseased. The sole factor that has saved many growers from total loss is that most
of the growing season occurs during cool weather--growth of the southern bacterial
wilt organism is favored by hot weather. Routine treatment of beds, alleys and all
tools with formaldehyde is essential.
SAssociate Plant Pathologist, Everglades Station, Belle Glade, and Entomologist,
Indian River Field Laboratory, Ft. Pierce, respectively.
- 2 -
Another disease, known as bacterial spot, costs hydroponic growers thou-
sands of dollars annually. The causal bacterium is seed-borne. A combined seed
treatment bichloridee of mercury) and foliage spray (Agri-Strep, Agrimycin, Phytomy-
cin, etc.) is a must for control of this disease.
Late blight is another serious disease, but can be controlled through the
proper use of any of several materials listed in Table 1.
Botrytis gray mold is a relatively new disease. If it appears the grower
should switch to Phygon or Fermate (see below).
Suggested Control Procedure:
1. Seed Treatments The material to use is bichloride of mercury (available at any
drug store). Dissolve it in water so as to provide a 1-2000 solution (7.3
grains in one quart of water).
Place seed in a cheesecloth bag (do not fill bag over 113 full) and im-
merse in the solution for five minutes. Gentle agitation during this period is
desirable. Next, rinse the seed in running water for 15 minutes then dry them
quickly by spreading in a thin layer in the sun, Store in a cool dry place (Note:
treated seed should not be stored for more than two months).
2. Seedbed Treatment: Formaldehyde lends itself very nicely to this treatment.
The following procedure should be used for maximum performance:
1) Remove all plant material from seedbeds.
2) Add formalin (37-40 percent formaldehyde) to water in the pumping
system at the rate of 1 to 2 gallons for each 100 gallons of water.
3) Pump this solution into the beds so as to cover the gravel.
I) Cover beds with sisal craft paper or some other gas-impervious material.
5 Allow to stand for 24 to 48 hours.
6) Next, use this same solution for drenching alleys, and at the same time
drench all tools, frames, etc,
7) Cover the alleys as in number (4) above and for the same period of time,
3. Fungicide Spray Program:
(Note: Spray on a $-day schedule throughout the season).
A, August through October. Streptomycin (200 ppm,) plus a neutral cop-
per (4 Ibs/lO00 gals.), This program should be started soon after
emergence is complete,
B, After October. Parzate (2 lbs, powder/l00), Dithane Z-78 (2 Ibs,/
100), Manzate (l1- lbs./l0O), Dithane M-22 (1 lbs/10) or Phygon
(3/l lb./100). If Botrytis becomes a problem, Phygon (3/4 lb./O)
or Fermate (4 lbs./100) should be used, Note: Fermate may not give
adequate control of late blight if that disease is a problems where.
as Phygon does give adequate control.
C. The following combination sprays are suggested for experimental
trials only and are to be used after October:
(1) Maneb (Manzate or 11-22) (1 lb./lOO) plus Phygon (Q lb./lOO).
(2) Zineb (Parzate or Dithane Z-78) (11 lbs./100) plus Phygon
(3) Maneb (1 Ib./100) plus Fermate (3 lbs/100).
(I) Zinab (li lbs./lO0) plus Fermate (3 lbs./100).
The important insects of hydroponic tomatoes are shown in Table 2,
Effective chemicals are shown in the right hand columns
Table 2. Common insects of hydroponic tomatoes and effective materials
for their control.
The Insect Recommended Material
1. Serpentine leaf miner Parathion
2. Southern Armyworm DD; TIE
3. Tomato fruitworm JDTj TEE
4. Tomato hornworm Parathionj TIE
.5 Stink bugs Parathion
6. Aphids Paration
The serpentine leafminer is a persistent pest in south Florida and will
appear on almost every crop. It is especially serious when old tomato fields are
abandoned in the area, since a large number of adult flies migrate from these old
fields into the hydroponic plantings. The tiny flies puncture the leaves and with
draw sap, leaving small light dots. The female deposits eggs in some of these punc-
tures. The egg hatches into a tiny maggot which tunnels, or "mines" the leaves, and
if plentiful enough the maggots will cause the leaves to turn brown and die. The
stems of young seedlings are often mined. Host of the pre-pupae drop into the gravel
among the tomato roots.
The adult southern arnmyorm is a night flying moth which deposits masses
of eggs on the tomato leaves. These hatch into small larvae which feed for a while
near the egg mass, and then scatter about the plants feeding upon the leaves, young
stems and fruit, The full grown worm is 1 to 1- inches long, and is characterized
by a slight hump on which is a dark band or spots near the head.
The tomato fruit worm adult is a moth which deposits eggs singly in the
evening. A few moths are capable of infesting many plants due to their habit of de-
positing a large number of eggs one at a time over a wide area. The larvae feed upon
the leaves and stems, and many find their way to green tomatoes in which they feed.
The full grown worm is nearly two inches long and is often highly colored.
The adult of the tomato hornworm is a large hawk-moth whose flight habits
resemble those of the humming bird. The adult lays its eggs singly about the tomato
plants. The emerging larvae which feed and grow at a rapid rate are characterized
by a long horn-like appendage at the rear end. The full grown worm is enormous in
size, about four inches long, but is difficult to locate because its color blends in
with the tomato plant. Defoliated portions of the plant serve as the most important
indicator of the wormts presence,
Several species of stink or plant bugs damage tomatoes by puncturing
leaves, stems, and fruit and withdrawing sap. They are especially injurious to the
Although aphids are seldom a problem on tomatoes where parathion is used,
they are capable of building up in large numbers where no control measures are
Suggested Control Procedure:
Fortunately, a combination spray of parathion and DDT will control most of
the common insects of hydroponic tomatoes. These chemicals are compatible with the
recommended fungicides and bactericides, if wettable powder formulations are used.
The following spray schedule is suggested:
For young tomato seedlings One-half pound 15 percent wettable parathion
plus 1 pound 50 percent wettable DDT in 100 gallons of water on a weekly schedule.
Apply spray to dry plants, since parathion may cause injury to young plants when
they are wet with rain or dew. If large numbers of adult leafminers are migrating
into the planting it may be necessary to spray twice each week with I pound parathion
per 100 gallons spray, adding DDT once each week.
For large tomato plants (6 to 8 weeks old and older): One pound 15 per-
cent parathion wettablee powder) plus 2 pounds 50 percent DDT per 100 gallons applied
every 7 to 10 days. If leafminers are severe, apply 1 pound of parathion twice each
week until infestation subsides; add DDT every other time. If hornworms or stink
bugs appear, use 2 pounds of 15 percent parathion.
Caution: Parathion is a very useful chemical on tomatoes, but it is high-
ly poisonous to humans, especially if taken into the mouth or lungs. The precautions
on the label must be read and carefully followed. All spray applications (insecti-
cide and/or fungicide) should be made immediately after harvest in order to allow
as much time as is possible between spraying and the next harvest. Fruits must be
thoroughly washed to remove excessive residues.