Southeastern U.S. Vegetable Crop Handbook - 2022 - 310

DISEASE CONTROL
SEED TREATMENTS
Seed sanitation to eradicate bacterial or viral plant pathogens: When treating
vegetable seeds, it is critical to follow the directions exactly, because germination can
be reduced by the treatment and/or the pathogen may not be eliminated. The effect of
a treatment on germination should be determined on a small lot of seeds prior to
treating large amounts of seed. Treatments should not be applied to pelleted seed, 2)
previously treated seed, or 3) old or poor-quality seed. A protective fungicide treatment
(see below) can be applied to the seed following treatment for bacterial pathogens.
Seed treatments to prevent damping off diseases: Most commercially available
vegetable seeds come treated with at least one fungicide and/or insecticide. Vegetable
producers who would like to apply their own seed treatment should purchase non-treated
seed. While many fungicides are labeled for use on vegetable seed, most
fungicides are restricted to commercial treatment only and should not be applied by
producers. Labeled fungicides can be applied to seed following treatment for bacterial
pathogens. Do not use fungicide treated seed for food or feed.
HOT WATER TREATMENT
By soaking seed in hot water, seed-borne fungi and bacteria can be reduced, if not
eradicated, from the seed coat. Hot water soaking will not kill pathogens associated with
the embryo nor will it remove seed-borne plant viruses from the seed surface.
1. Place seed loosely in a weighted cheesecloth or nylon bag.
2. Warm the seed by soaking it for 10 minutes in 100°F (37°C) water.
3. Transfer the warmed seed into a water bath already heated to the temperature
recommended for the vegetable seed being treated (Table 3-47). The seeds
should be completely submerged in the water for the recommended amount of
time (Table 3-47). Agitation of the water during the treatment process will help to
maintain a uniform temperature in the water bath.
4. Transfer the hot water treated seed into a cold-water bath for five minutes to stop
the heating action.
5. Remove seed from the cheesecloth or nylon bag and spread them evenly on
clean paper towel or a sanitized drying screen to dry. Do not dry seed in areas
where fungicides, pesticides or other chemicals are located.
6. Seed can be treated with a labeled fungicide to protect against damping off
pathogens.
CHLORINE BLEACH TREATMENT
Treating seeds with a solution of chlorine bleach can effectively remove bacterial
pathogens and some viruses (i.e., Tobacco Mosaic Virus) that are borne on the surface
of seeds.
1. Add 1 quart (946 ml) of Clorox®
bleach to 5 quarts (4.7 L) of potable water.
2. Add a drop or two of liquid dish detergent or a commercial surfactant such as
Activator 90 or Silwet to the disinfectant solution. Add seed to the disinfectant
solution (1 pound of seed per 4 quarts of disinfectant solution) and agitate
for 1 minute.
3. Prepare fresh disinfectant solution for each batch of seeds to be treated.
4. Rinse the seed in a cold-water bath for 5 minutes to remove residual
disinfectant.
5. Spread seeds evenly on clean paper towel or a sanitized drying screen to
dry. Do not dry seed in area where fungicides, pesticides, or other chemicals
are located.
6. Seed can be treated with a labeled fungicide to protect against damping off
pathogens.
HYDROCHLORIC ACID TREATMENT
Tomato seed can be treated with a dilute solution of hydrochloric acid (HCl) solution
to eliminate seed-borne bacterial pathogens such as Xanthomonas spp. (Bacterial
leaf spot), Pseudomonas syringae pv. tomato (Bacterial speck) and Clavibacter
michiganensis subsp. michiganensis (Bacterial canker). Hydrochloric acid can also
be used to remove TMV from the surface of tomato seed. Do not use HCL-treated seed
for food or animal feed.
1. Prepare a 5% solution of HCl by adding one part acid to 19 parts potable
water. Prepare the acid solution in a well-ventilated area and avoid direct
skin contact with the acid.
2. Soak seeds for 6 hours with gentle agitation.
3. Carefully drain the acid off the seed and rinse seed under running potable
water for 30 minutes. Alternatively, rinse the seeds 10 to 12 times with
potable water to remove residual acid.
4. Spread seeds evenly on clean paper towel or a sanitized drying screen to
dry. Do not dry seed in area where fungicides, pesticides, or other chemicals
are located.
5. Seed can be treated with a labeled fungicide to protect against damping off
pathogens.
Brussels sprout
Cabbage
Carrot
Cauliflower
Celery
Chinese cabbage
Collard
Cucumber 1
Eggplant
Garlic
Kale, Kohlrabi
Lettuce
Mint
Mustard, Cress, Radish
Onion
Pepper
Rape, Rutabaga
Shallot
Spinach
Tomato
Turnip
TRISODIUM PHOSPHATE TREATMENT
Tomato seed can be treated with trisodium phosphate (TSP) to eradicate seed transmitted
TMV. Do not use TSP-treated seed for food or animal feed.
1. Prepare a 10% solution of TSP (1 part TSP in 9 parts potable water). Trisodium
phosphate is available at most home supply or paint stores. Avoid direct
skin contact with the TSP solution.
2. Soak seed for 15 minutes in the disinfectant solution.
3. Rinse the seed in a cold-water bath for 5 minutes to remove residual
disinfectant.
4. Spread seeds evenly on clean paper towel or a sanitized drying screen to
dry. Do not dry seed in area where fungicides, pesticides, or other chemicals
are located.
5. Seed can be treated with a labeled fungicide to protect against damping off
pathogens.
TESTING SEED GERMINATION AFTER SEED TREATMENTS
Randomly select 100 seeds from each seed lot.
1. Treat 50 seeds using one of the sanitizers described above.
2. After the treated seed has dried and before application of a protectant fungicide,
plant the treated and non-treated seed separately in flats containing
planting mix according to standard practice. Label each group as treated or
non-treated.
3. Allow the seeds to germinate and grow until the first true leaf appears (to
allow for differences in germination rates to be observed).
4. Count seedlings in each group separately.
5. Determine the percent germination for each group: # seedlings emerged ÷ #
seeds planted x 100.
6. Compare percent germination between the treated and non-treated groups.
Percent germination should be within 5% of each other.
TABLE 3-47. RECOMMENDED TEMPERATURES &
TREATMENT TIMES FOR HOT WATER DISINFESTATION
OF VEGETABLE SEED
Vegetable Crop
Broccoli
Water Temperature
(°F/°C)
122/50
122/50
122/50
122/50
122/50
122/50
122/50
122/50
122/50
122/50
120/49
122/50
118/48
112/44
122/50
115/46
125/51
122/50
115/46
122/50
122/50
122/50
Soaking Time
(Minutes)
20 to 25
25
25
15 to 20
20
25
20
20
20
25
20
20
30
10
15
60
30
20
60
25
25
20
1 Cucurbits other than cucumbers can be severely damaged by hot water treatment and
should be disinfested using chlorine bleach.
310
2022 Vegetable Crop Handbook for Southeastern United States
Southeastern U.S. Vegetable Crop Handbook - 2022

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