Reduction of Pythium Damping-Off in Soybean by Biocontrol Seed Treatment.

spp. is one of the major groups of pathogens that cause seedling diseases on soybean, leading to both preemergence and postemergence damping-off and root rot. More than 100 species have been identified within this genus, with , , var , and being particularly important for soybean production given their aggressiveness, prevalence, and abundance in production fields. This study investigated the antagonistic activity of potential biological control agents (BCAs) native to the U.S. Midwest against spp. First, in vitro screening identified BCAs that inhibit var. growth. Scanning electron microscopy demonstrated evidence of mycoparasitism of all potential biocontrol isolates against var. and , with the formation of appressorium-like structures, short hyphal branches around host hyphae, hook-shaped structures, coiling, and parallel growth of the mycoparasite along the host hyphae. Based on these promising results, selected BCAs were tested under field conditions against six different spp. 26 used alone and a mix of 16 19 used as seed treatments protected soybean seedlings from spp. infection, as BCA-treated plots had on average 15 to 20% greater plant stand and vigor than control plots. Our results also indicate that some of these potential BCAs could be added with a fungicide seed treatment with minimum inhibition occurring, depending on the fungicide active ingredient. This research highlights the need to develop tools incorporating biological control as a facet of soybean seedling disease management programs. The harnessing of native BCAs could be integrated with other management strategies to provide efficient control of seedling diseases.