Use of Seed Treatments to Manage Fusarium Virguliforme.

Sudden death syndrome (SDS) on soybean [Glycine Max (L) Merr.] is caused by Fusarium virguliforme a disease known to cause significant yield loss. Infection can occur as early as one day after germination. Little is known about the effect of seed treatment to slow or prevent infection of this disease. The objective was to assess the effect of soybean seed treatment on SDS. Field studies were conducted at two locations in Iowa in 2008 with a history of SDS. The experimental design was a randomized complete block with four replications with a factorial combination of four cultivars within each maturity group (two resistant and two susceptible to SDS), and with and without sorghum seed infested with F. virguliforme. All cultivars were treated with a fungicide, insecticide, fungicide insecticide combination, and an experimental systemic fungicide seed treatment. Three growth chamber studies were also conducted using a randomized complete block design with eight replications with cone-tainers inoculated with F. virguliforme. In the field, foliar disease ratings started at R1 and continued until R7 on a 10 day interval. In the growth chamber, plants were rated for SDS starting at 14 days after planting and then at five day intervals. Due to the low disease incidence in the field studies no differences were observed among seed treatments or between inoculation treatments. Disease incidence averaged across both locations was only 12%. In the growth chamber, seed treatment differences were observed with the experimental fungicide seed treatment consistently reducing disease symptoms severity across all ratings by 0.50 (on a scale of 1 to 9) compared to all other treatments. Root health index ratings based were also assessed and all seed treatments were similar and did all reduced the root health index compared to the control. Studies will resume in 2009.