IPM : Publications : 1999 Annual Report : Snapbeans, Weeds and IPM

1999 Integrated Pest Management Annual Report

Snapbeans, Weeds and IPM

Weeds do not exist in isolation — they can influence other organisms within crop environments. Putting the research spotlight on weed biology can aid development of better integrated pest management practices for snapbeans, a crop widely grown in the Midwest.

Crops can tolerate varying degrees of weed competition with- out adverse effects on crop growth and yield. Because weed–crop competition is affected by both the timing of weed emergence and weed density, these factors are part of a study to develop economic thresholds for two troublesome weeds (redroot pigweed and large crabgrass) affecting snapbean production. These weeds are prolific seed producers, emerging from May to September during the main cropping season for snapbeans. At densities greater than two plants per row foot, redroot pigweed and large crabgrass emerging with the snapbeans reduce yield. Later-emerging weeds do not significantly affect yield. Weeds also can affect insect pests. Populations of two insect pests, potato leafhopper and bean leaf beetle, are being monitored as well to determine if changes in weed density affect the potential influence of these pests on snapbean production.

Snapbeans growing in rye mulch

Snapbean plot with pigweed

Reduced tillage–high residue systems can prevent soil erosion, improve soil tilth, and suppress weeds in vegetable crops. By changing the crop environment, these alternative production systems also can affect other pests and may lower crop yields. Recent small-plot research with cereal rye cover crops has shown that these systems provide effective weed control through midseason, decrease the incidence of white mold disease on snapbean, and reduce some insect pest problems (that is, leafhoppers). Snapbean yield was reduced in reduced-tillage systems due to soil compaction and allelo-chemical release by the rye. The use of strip tillage was found to reduce much of the adverse effects of cover crop mulches on vegetable crop yields, but additional modifications are needed to reduce risk and increase snapbean yields in reduced-tillage rye mulch systems.

Snapbeans with large crabgrass

Contacts:

John Masiunas, masiunas@uiuc.edu, NRES

Cathy Eastman, ceastman@uiuc.edu, INHS

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