RESPONSES OF SOIL INSECTS TO MIXED AND CONTIGUOUS PLANTINGS OF RESISTANT AND SUSCEPTIBLE SWEET-POTATO CULTIVARS

This study was designed to determine if the preference of soil insects for sweetpotato [Ipomoea batatas (L.) Lam.] cultivars is affected by the proximity of resistant or susceptible plant cultivars at various spacings. Comparisons were made for damage caused by wireworms (Conoderus spp.), Diabrotica spp., Systena spp., sweetpotato flea beetles (Chaetocnema confinis Crotch), and grubs (Plectris aliena Chapin; Phyllophaga ephilida Say) in previously reported resistant and susceptible cultivars. Field plots were planted with a resistant cultivar, a susceptible cultivar, or the two cultivars intermixed. Large roots exhibited more insect damage than medium and small roots. When plant spacing was increased, roots were larger and insect damage more severe. Mixed plantings of resistant and susceptible cultivars significantly reduced insect damage in the susceptible plants. Planting regime did not influence insect damage for the resistant cultivars.