Insect Population Response to Mixed and Uniform Plantings of Resistant and Susceptible Plant Material

Abstract

This study was designed to determine how the preference of an insect for a plant line is affected by the proximity of less or more attractive lines. The test insects and their host crops were the potato leafhopper, Empoasca fabae (Harris), on potatoes; the imported cabbageworm, Pieris rapae (L.), on cabbage; and the Mexican bean beetle, Epilachna varivestis Mulsant, on lima beans. Comparisons were made between infestations in previously reported resistant and susceptible crop cultivars or lines. Field plots were planted all in a resistant cultivar or line, all in a susceptible cultivar or line, or the two cultivars or lines intermixed. The plant array did not have a significant effect on the size of the Mexican bean beetle population in the resistant or susceptible cultivars. A mixed planting of cultivars preferred and nonpreferred by the imported cabbageworm accentuated the differences between the two cultivars, although an unknown character of the preferred cultivar reduced the differences. Nonpreference was more apparent in isolated pure stands of potato lines than when the preferred and nonpreferred lines were in the same plot.