This article is an introduction to the general processes and basic steps of how to use mustard cover crops to reduce soil borne diseases, such as Plectosporium, in pumpkin. Research using mustard plants to naturally biofumigate soil to allow for more normal yield and fruit quality, has been conducted in several states and Canada, sometimes with mixed results. The results of this trial will be released in a report later in the season.
The field intentionally selected for this trial was cropped to pumpkin in 2018 and exhibited high amounts of Plectorsporium infections on both plant and fruit. The general recommendation for a field infested with this disease would be to rotate away from cucurbits for 3-5 years. Instead of rotation, we are investigating the use of biofumigation as a means to reduce disease incidence.
In mid-April when conditions were suitable for direct seeding, Pacific Gold (6lb/A), Caliente 199 (10lb/A), and a 50/50 blend of the two were drilled into plots at the Western Ag Research Station in South Charleston. Prior to seeding, 100 lb/A of urea and 34 lb/A ammonium sulfate were broadcast and incorporated to increase the biomass and glucosinolate levels of the cover crop. Glucosinolates are the compounds responsible for the biofumigation effect and are released when the mustard plant tissue is macerated and incorporated into the soil. The production of these compounds peak during flowering.
Once peak bloom has been reached it is necessary to mow the plants, immediately followed by incorporation (such as rototilling), packing, and then sealing the soil with water. Once these steps have been performed, the glucosinolates are broken down into other compounds in the soil such as isothiocyanates, where they begin the biofumigation reactions. It is recommended to wait 7-10 days after incorporation to either direct seed or transplant. We seek to confirm the necessity of the waiting period by both seeding and transplanting pumpkins one day after incorporation; we’ll report if any negative effects are seen on the germination rate or growth of the transplants.
To hear more details about the trial and see all steps including the incorporation of mustard cover crop, watch this video posted to the OSU IPM YouTube channel: https://youtu.be/Taz-PhDphhA
If you have worked with mustard cover crops before and have any experiences positive or negative to share, please send them to me at firstname.lastname@example.org.