Occurrence and abundance of selected pest and beneficial arthropods in relation to peanut plant phenology, irrigation, and insecticides

Influence of plant phenology, irrigation, and insecticides on seasonal abundance of selected pest and beneficial arthropods in peanut was evaluated at Tifton, GA. Pest species included, Frankliniella fusca (Hinds), Stegasta bosqueella (Chambers), Heliothis zea (Boddie), Elasmopalpus lignosellus (Zeller), and Empoasca fabae (Harris). The seasonal abundance of beneficial arthropods, Orius insidiosus (Say), Geocoris spp., nabids, spiders, and parasitoids was also evaluated. Population estimates of these arthropods were compared during the 3-year study using whole plant, terminal, flower, and sweep net sampling methods.; The sampling efficiencies of the four methods varied with developmental stage and feeding behavior of a particular species. However, it was found that a combination of terminal examination and sweeping could yield valuable information about the seasonal abundance of most arthropods associated with peanut. Converted to quantitative values, i.e., "per plant" values, population estimates by these two sampling methods are likely to provide more reliable information than beat and shake methods presently used to sample peanut insects.; Thrips populations in terminals reached peak densities in early vegetative stages, but declined sharply at the onset of flowering. Densities of H. zea, E. lignosellus, and S. bosqueella coincided with peanut growth stages most susceptible to damage. Highest predator densities coincided with peak pest populations.; In 1986, overhead irrigation significantly reduced populations of thrips, red-necked peanutworm, and lesser cornstalk borer larvae, while increasing infestations by potato leafhopper. Irrigation had little impact on populations of corn earworm larvae or predators, with the exception of spiders whose populations were significantly higher in irrigated than in nonirrigated peanut.; Aldicarb applied at planting effectively controlled thrips and potato leafhopper infestations, but encouraged an increase in H. zea larval populations. Combined applications of aldicarb, methomyl, and chlorpyrifos controlled thrips, leafhoppers, and corn earworm. However, none of the insecticides had a significant effect on larvae of S. bosqueella or E. lignosellus. Populations of Geocoris spp., nabids, and spiders were reduced by multiple insecticidal applications. Under pest population levels encountered in this study, insecticides did not significantly increase pod yield.