Cotton Water Stress, Arthropod Dynamics, and Management of Bemisia tabaci (Homoptera: Aleyrodidae)

Abstract

The effects of plant water stress on beneficial and pest insects infesting Delta pine- 50 short-staple cotton, Gossypium hirsutum L., and Puma S-7 long-staple cotton, Gossypium barbadense L., were studied in 1993 and 1994 in large replicated field plots in central Arizona. Seasonal densities of eggs, nymphs, or adults of the sweet potato whitely, Belicia tabaci (Genius), were reduced 45-69% and 22-36% in plots irrigated weekly compared with those irrigated biweekly in 1993 and 1994, respectively. In 1993, DPL-50 had more white flies of, ill stages than Puma S - 7, but crop termination dates had no effect on seasonal densities of white flies. In 1994, fenpropathrin and faceplate insecticide applications provided greater control of white flies than buprofezin, an insect growth-regulating insecticide. Application thresholds of 1 adult whitely per leaf resulted in lower whitely densities than thresholds of 5 or 10 adults per leaf. In 1994, pink boll worm larvae, Pectinophora gossypiella (Saunders), were reduced in plots treated with fenpropathrin and faceplate and in plots treated for B. tabaci. at the threshold of 1 adult per leaf. More Lyes Hesperus Knight were found in plots irrigated weekly than biweekly in both years. Leaf water potentials (-bars), measured at 3, 7, or 14 d after irrigation in 1993, indicated greater plant water stress in cotton irrigated biweekly at 7 and 14 d after irrigation than in that irrigated weekly at 7 d after irrigation. Yields of seed cotton were greater at thresholds of 1 than at 5 or 10 adult white flies per leaf. Combining reduced plant water stress of weekly irrigation with fenpropathrin and faceplate applied at a threshold of 1 adult whitely per leaf provided the best control of B. tabaci.