Question
Dear Dr Laundry,
While researching ways to disinfect seeds from plants, came across a few protocols mentioning sodium hypochlorite bleach plus a non-ionic surfactant or wetting agent (like Tween 20) to help get into minute crevices and semi-hydrophobic spaces where pathogens might hide. Would you have a recommendation on what surfactant might be most compatible with Clorox bleach, or perhaps a similar feature is already built-in to a Clorox product which might be good for this particular type of disinfection?
Answer
This is such an unusual question. What types of seeds are you interested in disinfecting? Since Clorox® Disinfecting Bleach is EPA-registered as a disinfectant, recommendations for use need to be consistent with the EPA Registration for the product, which details all the approved ways to use the product.
I am curious about what seeds you are working with because there is some variation among the concentration of the bleach solutions recommended for the different seeds mentioned on the Master Label. For example, asparagus seeds should be washed for 40 minutes with continuous agitation in a 6000 ppm available chlorine solution before air drying. The recommended available chlorine solution solution for pepper and tomato seeds is 10,000 ppm. These are all bleach and water solutions; no surfactants/detergents are included in the instructions.
The Master Label also includes directions for disinfecting wheat and triticale germplasm for research or seed increase with a bleach solution made by mixing 1 part Clorox® Disinfecting Bleach with 4 parts water + 2ml/L Tween added (no item number specified). Seeds should be agitated in the bleach and water solution for 10 minutes, followed by a 15-minute rinse with clean running water, and then air dried. That’s about as close to a recommendation for a wetting agent as it gets. One other point I wanted to clarify is that these treatments are intended for seeds that will be planted or used for research — they should not be used for feed or food, and are not appropriate for growing something like bean sprouts where the seed is consumed along with the sprout.
You mentioned searching online for information. There are many great agricultural extension programs at different universities in the U.S. that issue recommendations for bleach use for disinfecting seeds. Read over the protocols carefully, paying close attention to the concentration of bleach they are using. Often, the research is older and the version of Clorox® Disinfecting Bleach that was used is at a lower concentration than what is available now. Just be sure whatever recommendation you are following takes into account the current 7.5% NaOCl concentration of our product so you don’t inadvertently work with too strong a solution.