Description

Abstract: Treatment timings of two insecticides with low water solubility, chlorpyrifos and fonofos, were compared as prophylactic treatments against damage to peanuts, Arachis hypogaea L., by southern corn rootworm, Diabrotica undecimpunctata howardi Barber, during 1988 and 1989 in North Carolina and Virginia. Treatments were applied at one of three dates: as a preplant broadcast or in a 41-cm band over the row at planting, in a 41-em band over the row at flowering (mid-June), or later at the more traditional pegging time (mid-July). Early planting and flowering treatments did not result in reductions in the level of control compared with later pegging applications. Peanut yield was quite variable, and few significant differences could be detected among treatments; however, several treatments significantly increased yield compared with untreated plots. Advantages to early application, if done without sacrificing late-season rootworm control, would include less vine damage during application, earlier-season control of other insect pests, and fewer problems with secondary pests. In addition, smaller plants would permit insecticide soil incorporation that would limit the exposure of granular material to birds (and potentially reduce avian risk) and decrease ultraviolet degradation.