Spatial Distribution and Behavior of TBW Larvae on Treated Plants, 1989

Abstract

A greenhouse study was conducted to measure the spatial distribution and behavior of third instar larvae on amitraz (ATZ)-treated and untreated plants. TBW eggs were obtained from ICI Americas' cypermethrin-resistant (R) and -susceptible cultures. Neonate larvae were placed on pinto bean diet in plastic cups and held in an incubator at 27 ± 2°C with a 12:12 (L:D) photoperiod until they reached third instar. Squaring cotton was sprayed with aqueous dilutions of ATZ using a CO2 pressurized (40 psi) backpack sprayer calibrated to deliver 4.4 gal/acre through 2, size 3X hollow-cone nozzles per row. The third instars were placed on the third mainstem internode below the shoot terminal of each plant 1 h following application of ATZ. Treatments were placed randomly in the greenhouse. Larval location and activity were observed on each plant at 15 min intervals for 6 h or until the larva left the plant. Locations recorded were shoot terminals, squares, leaf blades and stem/petioles. Vertical migration of the larva was measured by recording the number of the mainstem internode from which the plant structure arose where the larva was located. Feeding/scraping, resting, locomotion and spin-down were the larval behaviors recorded. The 6 treatments were replicated 20 times. The percent occurrence of each larva at each location, and larval behavior at each location for the 6-h observation period was a replicate.