"Herbicide Impact on Fusarium spp. and Soybean Cyst Nematode in Glyphosate-Tolerant Soybean"
Abstract
R.J. Kremer, USDA-ARS
P.A. Donald
A.J. Keaster
H.C. Minor, Univ. of Missouri
American Society of Agronomy
Title Summary Number: S03-104-P
Increased and frequent use of glyphosate associated with Roundup Ready (RR) soybean production can affect activities of rhizosphere and soil microorganisms. Glyphosate influence on interactions of soybean with soybean cyst nematode (SCN; Heterodera glycines) and rhizosphere fungi may have potential implication in future management. Field experiments were conducted to determine the impact of glyphosate applied to RR soybean on root and soil colonization by Fusarium spp. and SCN. In 1997 and 1998, RR soybean receiving glyphosate at 1X and 3X recommended rate had significantly higher incidence of Fusarium on roots compared with control (no glyphosate) at one Missouri site. In 1999, glyphosate, conventional herbicide mix (pendimethalin+imazaquin), and glyphosate+conventional were evaluated on four RR soybean varieties at eight sites. Frequency of Fusarium on roots increased 0.5 - 5X at 2 or 4 wk after application of glyphosate or glyphosate+conventional herbicides compared with the conventional herbicide alone. Soil Fusarium populations varied among sites. Effects on SCN reproduction were variable. Increased Fusarium colonization of RR soybean roots with glyphosate application may influence potential disease level
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