Virus Diseases of Greenhouse Tomato and Their Managment
Vegetable Disease Information Note 15 (VDIN-0015)
Charles W Averre, Extension Plant Pathologist
Guy V. Gooding, Research Plant Pathologist
of greenhouse and field tomatoes in North Carolina occasionally cause serious
damage and large economic loss. The amount of loss can vary from 5% to 90%
depending on the virus disease involved, the strain of the virus, the variety
of tomato, the age of the plant at infection time, the temperature during
disease development, the presence of other diseases, and the extent that
viruses have spread in the planting. The symptoms, means of spread, hosts,
sources, and control procedures for virus diseases growers are likely to
encounter are summarized in table 1. In order to control
a virus problem it must be properly identified. Terminal shoots may be sent
to the Plant Disease and Insect Clinic at NCSU by the county agent for an
accurate diagnosis. With the exception of TMV, most viruses attacking tomatoes
survive only in living plants or briefly in insects. They are spread primarily
by aphids. Very few viruses are seed-borne. Usually the initial field distribution
of diseased plants tend to be spotty and concentrated along the edges of
the field. Some varieties are more susceptible than others. (See Vegetable
Disease Information Note No. 6).
important virus diseases on tomatoes in North Carolina is tobacco mosaic
virus (TMV), but other viruses may cause significant losses. There are
many strains of TMV and a few which occur in North Carolina are very damaging.
The common ones only cause a mild mosaic. TMV can survive many months
outside a living plant or insect, on tools, greenhouse frames, sawdust,
and in the soil; in dried leaves such as in cigarettes it can survive
for many years. It is rarely transmitted by insects. It is easily spread
by touch from diseased plants or from contaminated objects. TMV can be
seed-borne; however, the magnitude of seed with virus in contaminated
lots is usually under two percent, but with subsequent handling of plants
all plants usually become infected before picking.
Control of viruses on tomato is based on a total program all year. By
following these procedures you will reduce virus diseases and losses in
a tomato crop.
1. Summary of virus diseases and their control. Symptoms may vary
greatly depending on the type of virus, time of infection, and growing season
(those with asterisk are commonly found in North Carolina).
Obtain seed from reputable sources that have been fermented or treated
with acid or bleach by the seedsman. If seed has not been treated, proceed
as follows: Mix 2 pints of 5.25% sodium hypochlorite solution (household
bleach eg. Clorox) in 8 pints of water. Wash one pound of cleaned, fresh
or dry, tomato seed in one gallon of the mixture for 40 minutes. Provide
gentle and continuous agitation. Remove seed and spread on paper to
air dry promptly. Prepare fresh bleach solution for each batch of seed.
Caution and remarks: (1) Beginners should try this seed treatment on
inexpensive seed prior to treating large lots. (2) Seed germination
may be reduced with some lots of seed. (3) Research has shown that this
seed treatment is enhanced by prewashing the seed for 15 minutes in
a solution of trisodium phosphate (one ounce of TSP in two quarts of
water). (4) Do not recontaminate the seed by placing in used containers
early in the season to reduce initial infection and spread. It may be
a good idea to spray weeds bordering the field with an aphicide prior
to seeding or planting the field, and all annual weeds in the field
should be destroyed. Avoid planting tomatoes close to established cucumber,
squash, potato, tobacco, and pepper fields. Greenhouses containing tomatoes
should be bordered by at least 150 feet of turf or pavement.
stakes, tools, tables, etc. by: (1) heating or steaming at 300 degrees
F for 30 minutes; (2) soaking 10 minutes in 1% formaldehyde or a 1:10
dilution of a 5.25% sodium hypochlorite (10% Clorox) solution, do not
rinse; or (3) by washing (enough to clean) in detergent at the concentrations
recommended for washing clothes or dishes. Keep all solutions fresh.
Spray the plant
bed prior to pulling or handling plants (24 hours) with whole or skim
milk at the rate of 0.5 gallon per 100 square feet of beds; thorough
coverage of plants is important.
For tomato production,
seed in individual pots (peat pots, etc.) and do not touch or handle
plants prior to setting in the field or greenhouse. Discard pots with
seedlings that show leaf twisting, mosaic, or unusual growth. Do not
touch other seedlings while discarding them.
Dip hands in milk
while handling plants every 5 minutes (more often if different lots
of plants are handled). Rubber gloves will protect hands.
Remove and destroy
diseased plants early in the season. Do not touch healthy plants with
the diseased plants when removing them.
tools, and hands on a regular basis while pulling, pruning, trellising,
harvesting, and spraying plants, and when moving from one row or area
plants in the bed, field, or greenhouse as soon as possible after harvest.
crops with small grain, corn, or pasture. Avoid following tomato crops
after crops of tobacco, pepper, eggplant, or cucurbits.
Means of Spread
mosaic* (TMV, tobacco and tomato strains)
depending on strain. Leaves light green or yellow mottling, rough
edges turn down. Plant Dwarfed. Fruit small, poor set, brown streaks.
Shoestring of leaves may occur on young plants.
hands, tools, etc.
tobacco, petunia, horsenettle, jimsonweed, Jerusalem cherry, nightshade,
ground cerry, plantain, others
tobacco products, tools, seed, perennial weeds
disease-free plants, milk, bleach, detergent, steam, head, soil fumigation.
Avoid tobacco products and plants.
to TMV, upper leaf may be very narrow and twisted giving them a shoestring
appearance that may be confused with 2, 4-D type injury. Later excessive
number of lateral leaflets are produced. Plants may be dwarfed or
flowers, vegetables, milkweed, ground cherry, horsenettle, pokeweed,
jimsonweed, marigold, petunia, zinnia, cucumber, melons, celery,
no plant closer than 100 ft. from weeds or flowers. Control aphids.
streak TMV + PVX (Potato virus X or CMV)
affects large plants, dwarfed, spindly appearance, rolling and withering
of leaves. Long brown streaks on petioles and stems. Irregular ripening
of fruit, light brown sunken spots on green fruit.
as for TMV and aphids if CMV involved.
as for TMV and CMV
as for TMV and CMV Irish potato
as for TMV. Avoid potato or potato plantings near the planting. Control
aphids. Temperatures above 100 F for a few days will attenuate PVX
virus Y* (PVY)
brown dead areas between veins in leaflets near maturity, yellowing
along veins, faint mottling on leaves; petioles curved downward; stems
with purple streaking; symptoms usually become mild, but severe symptoms
develop if TMV is present.
and leguminous plants
and pepper. Usually does not overwinter in North Carolina.
not plant close to potato, tobacco or pepper fields. Do not obtain
plants from south Florida. Control aphids.
leaflets cupped, petioles bent downward. Stunting, similar to PVY
except not as severe and no stem or fruit mottling.
similar to PVY
horsenettle, ground cherry
as for PVY.
and tomato ringspot (TRSV)
or zigzag lines on foliage, occasionally on stems, petioles, and fruit.
On fruit, rings are often concentric.
nematode, thrips, mites, grasshopper, flea beetles
extensive; annuals, weeds, vegetables, ornamentals, tobacco, soybeans
not plant closer than 100 ft. from weeds or flowers. control all insects.
or bronze colored flecks on middle or lower leaves and calyx or stems
and petioles. Stunting, black depressed spots.
extensive on annuals, bulb crops, and weeds.
not plant closer than 100 ft. from weeds or flowers. Control thrips.
of terminal tips, much branching, bushy appearance of plant. Fruit
seedless, distorted, and production reduced.
plants, lettuce, spinach, weeds and many others.
not plant closer than 100 ft. from weeds or flowers. Control aphids.
Information Notes Home Page
Carolina Insect Notes
Carolina Agricultural Chemicals Manual
with a specific problem, contact your local
North Carolina Cooperative Extension Service
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of specific chemicals are based upon information on the manufacturer's
label and performance in a limited number of trials. Because environmental
conditions and methods of application by growers may vary widely, performance
of the chemical will not always conform to the safety and pest control
standards indicated by experimental data. All recommendations for pesticide
use were legal at the time of publication, but the status of registration
and use patterns are subject to change by actions of state and federal
regulatory agencies. 08/91
Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people regardless
of race, color, national origin, sex, age, or disability. North Carolina
State University at Raleigh, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating.
Reformatted Dec. 2000 by A.V.