Soybean Foliage Insects in Conservation Tillage Systems: Effects of Tillage, Previous Cropping History, and Soil Insecticide Application

Abstract

A 3-yr study was initiated to examine individual and interactive effects of tillage (conventional [moldboard plowing], reduced tillage, and no tillage); previous cropping history (corn, Zea mays L., versus soybeans, Glycine max Merrill); and soil insecticide application (phorate versus none) on insect communities inhabiting soybean foliage. Although, as expected, insect abundance varied seasonally and yearly, there were a number of cropping, tillage, and toxicant effects on herbivore and predator species. Japanese beetle, Popillia japonica Newman, populations were influenced more consistently by previous cropping history, with more beetles following corn, than they were by tillage, although highest beetle density occurred in reduced-tillage systems. Neither tillage treatment, previous cropping history, nor insecticide application significantly affected population density of green cloverworm, Plathypena scabra (F.). Potato leafhopper, Empoasca fabae (Harris), numbers were consistently greater in moldboard-plowed than in either reduced- or no-tillage treatments. Also, soil insecticide application lowered potato leafhopper density during 1 yr of the study. Grasshopper density was lower in moldboard-plowed than in reduced- and no-tillage treatments. Tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), were influenced by both tillage and previous crop treatments. Numbers of nabids (dealt with collectively), the most abundant predator collected during the study, were reduced with soil insecticide treatment and were positively affected by no-tillage practice and having soybeans as a previous crop. Results demonstrated that three management practices, tillage, previous cropping history, and soil insecticide application, can all have separate and interactive influences on foliage insect communities on soybeans, even when these practices impact most directly on the soil.