As we head into March, we begin to prepare for spring gardening once again! This includes tasks like wrapping up any necessary winter pruning and ordering seeds to plant for the upcoming year. With internet shopping of seed catalogues being more accessible than ever, many people will find that they can purchase the exact crop and cultivar they want with the push of a button. Varieties can even be filtered by yield or disease resistance.

Other people however, may wish to use heirloom seeds from their own or a neighbor’s garden, or organic seeds that aren’t pre-screened or treated for seedborne diseases. Although gardeners may have grown to anticipate some losses with these seeds due to seedborne diseases, a solution exists for many in the form of a hot water seed treatment (HWST).

What is a hot water seed treatment (HWST)?

It is exactly what you might expect: hot water is used to kill pathogens present on the surfaces of seeds before they are planted. For some types of plant diseases, this is an effective means to reduce disease incidence and give young plants the opportunity they need to become established and grow well. Seeds are “prepped” for treatment by first being submerged in a lukewarm water bath of 100 degrees Fahrenheit for 10 minutes. The seeds can then be moved to a bath set at the “treatment temperature”, which varies by crop type. After treatment, the seeds are gently, but thoroughly dried-off so they do not germinate prematurely.

Pure distilled water is pumped into the water baths.
Our equipment can precisely regulate water temperature!
An aquarium air bubbler helps move water and decrease damage to seeds that may overheat by staying still
The bubbler is kept at the base of the water bath using some removable weights (washers!)
The seeds are ready for the plunge!
Quick, gentle drying using only a fan is important so seeds are not damaged.
HWST process in photos. Photo credit: Nick Goltz, DPM

What types of seeds can undergo HWST?

Many types of seeds can undergo HWST for disease mitigation, but generally it is performed on small and hardy seeds. Large, fleshy seeds such as beans or pumpkin seeds may benefit from HWST in terms of disease reduction, but are more sensitive to damage from the hot temperatures and may have accordingly lower germination rates. Therefore, we only recommend HWST with seeds whose germination rates have been shown to be minimally impacted by the high temperatures. Additionally, seeds that have already been treated with HWST or fungicides, or those that have seed coatings (often these are a different color than uncoated seeds), should not be treated.

What diseases will HWST target?

There is ongoing research into what diseases can be successfully mitigated with HWST. Treatment efficacy varies by crop, but generally the diseases are those that will show up shortly after germination, while the plants are still seedlings. The UConn Plant Diagnostic lab and other university extension services that offer HWST will list the types of plants recommended for treatment and the diseases that can be controlled. Visit https://plant.lab.uconn.edu/hwst/ to find out more. The UConn PDL is funded, in part, by the state of Connecticut and the USDA through IPM Extension Implementation and National Plant Diagnostic Network grants.

Nick Goltz, DPM