Insect Distribution in a Spring Pea-Winter Wheat-Spring Barley Crop Rotation System

Abstract

The effects of tillage method (conventional or conservative) and weed management level (recommended or minimum) on insect distribution in a wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and pea (Pisum sativum L.) rotation were studied. Aphids were the major insect species on winter wheat and spring barley, but were not of economic importance. Beneficial species impacted aphid population levels by maintaining their numbers below economic thresholds. Tillage method and weed management level had limited impact on aphid and beneficial insect populations. Pea leaf weevil (Sitonia lineatus [L.]) and pea weevil (Bruchus pisorum [L.]) populations reached economic injury levels in 1992; two insecticide applications were needed. Pea leaf weevil populations did not reach economic levels in 1993; however, pea weevil populations reached an economic level at flowering stage and an insecticide was applied. Pea leaf weevil populations were higher in conventional tillage plots compared with conservation tillage plots. Early-season insecticide applications suppressed beneficial insects in the pea plots.