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POSTERS: Integrated pest management

Variety genetics and oomicide seed treatments effect on stand, health, and yield of soybeans under Phytophthora sojae disease pressure
Austin Mccoy - Michigan State University. Darcy Telenko- Purdue University, Loren Giesler- University of Nebraska-Lincoln, Adam Byrne- Michigan State University, Martin Chilvers- Michigan State University, Anne Dorrance- The Ohio State University

The causal agent of Phytophthora stem and root rot, Phytophthora sojae, is a major pathogen of soybean. Management of P. sojae consists of cultivars with effective resistance genes, partial resistance (field tolerance) and the use of seed treatments containing oomicides such as ethaboxam, mefenoxam, and/or oxathiapiprolin. In this study, soybeans were inoculated with P. sojae to investigate the interaction of variety genetics and seed treatment on soybean health and yield. Nine cultivars with different Phytophthora resistance packages were treated with three different seed treatments: 1.) non-treated, 2.) ipconazole and clothianidin, and 3.) ipconazole, clothianidin, ethaboxam and mefenoxam. Soybean stand and dry weights were recorded at VC, V2 and R4. Quantitative polymerase chain reaction (qPCR) of soybean roots was performed at V2 and R4 to assess levels of colonization by P. sojae throughout the season. Soybean stand and plant dry weights were significantly increased with treatments containing oomicides in 9 and 5 of the cultivars tested, respectively. Significant increases in yield were observed in the oomicide containing seed treatment in 2 varieties. Significantly, this study finds that oomicide seed treatments are useful in protecting seed, allowing for increased emergence under disease pressure.