Management strategies to improve soybean yield in high pH soybean cyst nematode infested fields

Abstract

Soybean cyst nematode (Heterodera glycines', SCN) causes the greatest yield losses of all diseases on soybean [Glycine max (L.) Merr.] in Iowa. Growing SCNresistant varieties in rotation with non-host crops and SCN-susceptible varieties is the current management recommendation for SCN in Iowa. Previous research has shown that SCN population densities are positively correlated with soil pH. The correlation may reduce the efficacy of the current SCN management recommendation in northern and central Iowa, which is located in the Des Moines lobe area, a calcareous soil area with high pH soil. The hypothesis for this research is that additional management strategies, such as the use of a nematicide (aldicarb), may need to be considered added to the current SCN management recommendations in Iowa. The objective of this study was to evaluate the effect of nematicide in combination with SCN-resistant soybean varieties on grain yield and SCN population densities in fields with different soil pH. Main plots were two planting dates (early versus late May). The sub-plots were four rates of aldicarb [2methyl-2(methylthio) propionaldehyde O-(methylcarbamoyl) oxime], applied in-furrow (0.0, 0.8, 1.7 and 2.5 kg a.i. ha1), and the sub-subplots were ten glyphosate-resistant soybean varieties with different reactions to SCN. The experiment was conducted at two northern locations, one central, and one southern location in Iowa from 2004 to 2005. Soil samples were collected from each plot at planting and at harvest to determine the initial (Pi) and final (Pf) population densities of SCN. Overall, early planting date improved yield. This improvement may be a combination of increased biomass accumulation and diapause of SCN eggs early in the spring. Grain yield and SCN population densities were not influenced by aldicarb. Differences in yield were observed among varieties. However, all