Effect of Sweet Potato Cultivar on Efficacy and Persistence of Entomopathogenic Nematodes for Control of Cylas formicarius

Abstract

Control of the sweet potato weevil, Cylas formicarius (F.), with different biological and chemical insecticide treatments was evaluated on two cultivars of sweet potato, Ipomoea batatas (L.) Lam. cvs. Jewel and Picadito, differing in susceptibility to C. formicarius. The effectiveness of two entomopathogenic nematodes, Steinernema carpocapsae (Weiser) All strain and Heterorhabditis bacteriophora (Poinar) HP88 stram, were compared with that of two chemical insecticides made in combination. Weevil control and nematode persistence (recycling) were evaluated. Weevil counts did not differ between cultivars nor among biological and chemical insecticide treatments during the first sampling period. On the second sampling period, numbers of live and nematode-infected weevils were higher on 'Jewel than on 'Picadito. Weevil counts were lowest on plants treated with All followed in increasing order by those treated with chemical insecticides, HP88 and nontreated plants. Root damage and percentag