Interaction of soybean cyst nematode with cropping practices and winter annual weeds

Valerie Ann Mock, Purdue University

Abstract

Soybean cyst nematode (Heterodera glycines; SCN) has been found in most soybean producing region of the U.S. Six winter annual weeds and one cool-season perennial have been reported to be alternative hosts for SCN. When SCN winter weed hosts are at low densities in the field, SCN population densities have been shown not be influenced by winter weed management. Often times soybean production fields have combinations of SCN host and non-host plants in the fall. As well as the winter annual weeds, volunteer glyphosate-resistant soybean can also occur in fields after harvest. Therefore, the objectives of this research were to determine if fall winter annual weed, and soybean removal timings influence SCN population densities and if combinations of host and non-host plants influence SCN population densities. This research found that SCN cyst counts were higher with two SCN-susceptible plants than with one SCN-susceptible plant plus one SCN-resistant plant. SCN egg counts per pot and per cyst were higher with two SCN-susceptible plants than with one or no SCN-susceptible plants. In a microplot study, we found that SCN egg populations were higher in plots with Lamium spp. plus volunteer soybean than fallow plots or plots with only Lamium spp and had no winter weed removal time. Plots with October and December weed removal timings did not show a reduction in SCN egg counts until the following August. In a longterm field study we found that SCN egg counts were not influenced by fall and/or spring winter weed control timings when weed densities were approximately 111 plants m-2; however, plots with a soybean corn rotation had lower SCN counts than plots with continuous soybean in the fall. The results from these experiments suggest that crop rotation with an SCN non-host is a more valuable SCN management tactic than control of winter weeds at moderately high densities. However, it may be important to control SCN alternative hosts during the time between late summer and harvest when soil temperatures are conducive for SCN egg hatch and juvenile root penetration.

Degree

M.S.

Advisors

Johnson, Purdue University.

Subject Area

Agronomy|Plant sciences

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