Population Response of Soybean Cyst Nematode to Long Term Corn–Soybean Cropping Sequences in Minnesota

Abstract

Soybean cyst nematode [Heterodera glycines Ichinohe] (SCN) can reduce soybean [Glycine max (L.) Merr.] yields. Rotating soybean with a nonhost crop usually reduces SCN populations. Cropping sequence experiments initiated in the early 1980s at two Minnesota locations were monitored in 1996, 1997, and 1998 for changes in SCN egg densities. Cropping sequences were: (i) 5‐yr consecutive corn (Zea mays L.) alternated with 5‐yr consecutive soybean, (ii) continuous monoculture of each crop, (iii) annual alternation of two cultivars within a continuous monoculture of each crop, and (iv) annual rotation of each crop. In 1989, SCN was detected in several of the plots at both locations. By 1996, all cropping sequences had detectable populations of SCN eggs at both locations, regardless of whether the land had been planted to continuous corn since the early 1980s. Lowest densities of SCN eggs were typically found in cropping sequences that involved continuous corn and where corn had been planted for the last three or more years, whereas highest levels of SCN eggs were found in cropping sequences that involved continuous soybean and where soybean had been planted for the last two or more years. These results suggest planting a nonhost to SCN for as long as 5 yr on infested land will not eliminate future problems with this pathogen. In addition, the results suggest that at least a portion of the crop sequence effects on yield has a soil microbiological basis involving mechanisms that are specific to a location.

The effect of the interaction of various spawn grains with different culture medium on carpophore dry weights and stipe and pileus diameters of Lentinus squarrosulus (Mont.) Singer

“…In order to test the main and interactive effects of spawn grain, media, oil type and rate of amendment, pileus and stipe diameter, stipe length and wet and dry weights of fruiting bodies were recorded and the data subjected to factorial analysis of variance (Porter, 2001). When significant differences were determined for the main effects or their interactions (p 0.05), comparisons among means were made using Duncan's multiple range test (Snedecor and Cochran, 1987;Sullivan and Sullivan, 2001).…”

Microbial Population and Community Dynamics on Plant Roots and Their Feedbacks on Plant Communities

“…Rather, as most soil pathogens are host specific, their population densities are managed by rotation with nonhost crops. The corn-soybean rotation that dominates much of agriculture in the United States, for example, is motivated by the escape of host-specific pathogens (bacterial, fungal, and oomycete) and nematodes (19, 23, 98, 112). …”

The beneficial root endophyte Piriformospora indica reduces egg density of the soybean cyst nematode

“…Various strategies have been employed to suppress the damage caused by the SCN (Porter et al, 2001). These include crop rotation and other cultural practices, resistant cultivars, and nematicides (Koenning et al, 1993;Riggs and Schuster, 1998;Schmitt, 1991;Young and Hartwig, 1992;Young, 1998a,b).…”