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Poster: Biology & Disease Mgmt: Cultural Control


Study of the influence of winter rye on soybean seedling and root rot diseases
G. ARALDI-DA-SILVA (1), T. Kaspar (2), M. Helmers (1), D. Mueller (1), L. Leandro (1) (1) Iowa State University, U.S.A.; (2) USDA, U.S.A.

Cover crops can enhance or suppress plant diseases, but little is known about the effect of cover crops on soybean diseases. In 2015, the effect of winter rye (Secale cereale L.) cover crop on soybean seedling and root rot was studied at two experimental sites, Boyd and ISUAG-USB, in Ames, IA. Both sites were under a no-till corn-soybean rotation. Cover crop treatments were rye and no rye, at Boyd; and early termination rye, late termination rye, and no rye, at ISUAG-USB. Variables assessed were soybean stand, root rot severity, dry plant weight, healthy green leaf area (HGLA), and yield. Root rot severity was visually assessed on a percent scale, and HGLA was measured as canopy percent reflectance using a hand-held radiometer. At Boyd, soybean stand (P=0.68) and yield (P=0.61) were not affected by treatment, but healthy green leaf area (HGLA) was higher in rye plots (P<0.001) compared to plots with no rye. At ISUAG-USB, no rye plots had more soybean stand (P=0.08), greater yield (3105 ± 304 kg/ha) (P=0.07), and higher HGLA (P<0.001) compared to plots with late termination rye. Early termination rye did not differ from late termination and no rye treatments for any variables. No difference in dry plant weight and root rot severity were observed between treatments at both sites (P>0.2). Site variables, as well as cover crop treatments, can influence soybean crop response. This study is going to be repeated in 2016, and additional research is underway to quantify Fusarium and Pythium populations at both sites.