Hot Water Treatment of Seeds

Gordon Johnson, Extension Vegetable & Fruit Specialist;

We have had an increase in bacterial diseases of vegetables that are seed transmitted such as black rot of cole crops.

Hot water treatment of seeds is a method to eliminate certain seed borne diseases of vegetable crops. This treatment has the benefit of killing pathogens that may be found on and within the seed coat.

From the Mid Atlantic Commercial Vegetable Production Recommendations:
“Seed heat-treatment follows a strict time and temperature protocol, and is best done with thermostatically controlled water baths. Two baths are required: one for pre-heating and a second for the effective pathogen killing temperature. The initial pre-heat treatment is 10 minutes at 100ºF (38ºC). The effective temperature treatment and time in the second bath differ between crops; protocols for several important crops are listed in Table E-10. Immediately after removal from the second bath, seeds should be rinsed with cool water to stop the heating process and dried on screen or paper. Seeds may be re-dusted with fungicide if desired. Pelleted seed is not recommended for heat treatment. Heat treat only seed that will be used during the current season. See crop sections for specific seed treatment recommendations.”

List of seeds that can be treated, treatment times and temperatures, and diseases controlled can be found at

The University of Delaware Extension Vegetable program has the equipment to hot water treat seeds. Please contact Gordon Johnson or Emmalea Ernest to arrange to hot water treat seeds.