Date of Award

1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

Abstract

A small plot study to determine the effects of a "as-needed" and "full-season" insecticide regime on the major arthropods, growth, and yield of cotton was conducted over a three year period (1982-1984). In the "as-needed" regime, acephate (4 g/kg of seed) was applied as a seed treatment at planting and application of foliar insecticides were initiated when cotton insect pests reached the threshold level. In the "full-season" regime, aldicarb (0.05 kg/ha) was applied in-furrow at planting and application of foliar insecticides were initiated when squares reached 1/3 grown and continued on a six to seven day schedule throughout the season. Aldicarb and acephate applied at planting gave good control of thrips, primarily Frankliniella fusca Hinds, and cotton aphids, Aphis gossypii Glover, for a period of 25 and 15 days after planting, respectively, and significantly (P < 0.05) increased cotton plant height and leaf area 40 to 45 days after planting. Repeated applications of acephate (0.28 kg/ha) applied as a foliar spray significantly (P < 0.05) reduced tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), and cotton fleahopper, Pseudatomoscelis seriatus (Rueter), infestations and predaceous arthropod populations below that of the control. Heliothis (larvae) terminal and square infestations were found to develop about 13 days earlier in the "full-season" than "as-needed" regime. The use of aerial ultra-low-volume spray techniques for control of Heliothis spp. and the boll weevil, Anthonomus grandis Boheman, were investigated. During the summer of 1983 two replicated field studies were conducted to evaluate the biological performance and yield involving 0.067 kg/ha cypermethrin applied by air in three insecticide carriers: (1) 2.34 l/ha vegetable (cottonseed) oil; (2) 2.34 liters vegetable oil containing 7% wt/wt emulsifier (Triton('R) N-57) plus water to make 9.34 liters total volume/ha; and (3) 18.68 l/ha water. In 1984, one replicated field study was conducted involving 0.067 kg/ha cypermethrin applied in two insecticide carriers: (1) 2.34 l/ha vegetable oil and (2) 18.86 l/ha water. Cypermethrin gave adequate control of Heliothis spp. and boll weevil infestations when applied in the three insecticide carriers. The insecticide carriers which contained vegetable oil gave numerically, but not statistically significant (P > 0.05), better control of the Heliothis infestation than did the 18.68 l/ha water treatment. (Abstract shortened with permission of author.).

Pages

225

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