SUPPRESSION OF <I>HETERODERA GLYCINES</I> IN A SOYBEAN FIELD ARTIFICIALLY INFESTED WITH <I>PASTEURIA NISHIZAWAE</I>

Abstract

Noel, G. R., N. Atibalentja, and S. J. Bauer. 2010. Suppression of Heterodera glycines in a soybean field artificially infested with Pasteuria nishizawae. Nematropica 40:41-52. In 1999, microplot soil infested with Pasteuria nishizawae was added to an ongoing tillage and crop rotation study to determine the effectiveness of P. nishizawae in managing Heterodera glycines. Population dynamics of H. glycines was monitored each year through 2005 as numbers of eggs per 100 cm3 soil at planting (Pi) and at harvest (Pf) of soybean cultivars either resistant or susceptible to H. glycines. A reproduction factor, Pf/Pi (Pi > 0), also was calculated and soybean yield was determined. Infestation of field soil with P. nishizawae had significant effects on population dynamics of H. glycines. Overall, Pi was lower in P. nishizawae-infested plots than on non-infested plots, with means of 320 ± 80 and 580 ± 80 eggs/100 cm3, respectively. Plots infested with P. nishizawae had similar or lower Pf than the non-infested plots, and Pf/Pi was, on average, lower in P. nishizawae-infested plots than on non-infested plots, 8.0 ± 2.1 compared with 14.0 ± 1.9. With only one exception in 2000, yield of soybean grown in P. nishizawae-infested plots was similar or greater than that of non-infested plots. The resistance or susceptibility of the soybean cultivar to H. glycines also had significant effects on population densities, since Pi, Pf, and Pf/Pi were similar or lower on the resistant cultivar than on the susceptible cultivar, except in 2005 when Pf and Pf/Pi were lower on the susceptible cultivar. In five of seven years, yield of the resistant cultivar was greater than that of the susceptible cultivar except in 2002 when yields were similar and 2005 when yield of the susceptible cultivar was greater. Tillage method had no effect on population densities of H. glycines. However, yield was higher following conventional tillage than for no tillage, with means of 2740 ± 40 versus 2520 ± 40 kg/ha. In this study, P. nishizawae was successfully transferred to a soybean field, became suppressive to H. glycines, and was associated with an increase in soybean yield.