Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/1999
Publication Date: N/A
Interpretive Summary: Insects are a major economic pest in crop production throughout the world. Most research regarding insect pests focuses on a specific insect that plagues one crop, during a single season or during multi-seasons. Normally, only one specific practice, such as tillage, would be evaluated as to its effect on insect populations. Rarely will the effect of an entire system on insect populations be investigated. Until now, there has not been any research to determine the effect of long-term rotations, tillage, and weed management levels on seasonal distribution of selected pests. In winter and spring cereals beneficial parasitic wasps and predators such as nabids and lady beetles maintained or even suppressed aphid populations below economic thresholds. Generally, tillage methods and weed management levels (herbicides applied or weeds present) had limited impact on aphid or beneficial populations. In spring dry peas, beneficial insects were not prevalent and major species (pea leaf weevil and pea weevil) were controlled chemically. Conservation practices such as reduced tillage and minimum weed management do not increase insect pest crop damage in wheat, barley and pea.
Technical Abstract: The effects of tillage method (conventional or conservation) 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.