Soil amendments with Brassica cover crops for management of Phytophthora blight on squash

Phytophthora blight induced by Phytophthora capsici is responsible for serious yield loss in vegetable production in the United States and other countries. This study was conducted to evaluate the efficacy of Brassica cover crops used as soil amendments for managing Phytophthora blight of squash.

In greenhouse studies, disease incidence on squash plants was significantly reduced by soil amendment with mustard shoots or roots used at 1 and 2.5% (plant tissue/soil, w/w). The shoots of canola used at 1 or 2.5% also suppressed disease, while the roots of canola or other crops did not reduce disease significantly. In field studies, soil amendments with mustard and canola provided the greatest disease reduction and increased squash yield significantly compared with the non-treated control. Mustard and canola did not appear to be susceptible to P. capsici.

The results indicated that some Brassica crops, particularly mustard and canola, had the potential to significantly reduce Phytophthora blight on squash when used as soil amendments. As P. capsici has a remarkable ability to develop resistance to chemical fungicides, use of effective Brassica cover crops could be a biorational alternative to fungicides and a valuable component in developing integrated disease management programs.