Abstract
Abstract Hancock variety cotton was planted Apr 23 on Grenada silt loam at the West TeTin. Expt. Sta., Jackson, TN. Four-row plots, 40 ft long were replicated 4 times in a randomized complete block design. The entire plot area was sprayed Aug 1 with methyl parathion (1. 0 lb ai/acre) to remove beneficials and encourage a bollworm outbreak. The number of bollworm eggs and larvae in terminals exceeded the recommended threshold level on Aug 8. Bollworm pressure was moderate for the subsequent 10-day period. Insecticides were applied Aug 8, 14, and 19 with a 4-row boom at the rate of 9.4 gal of mixture per acre (3 mph, 40 psi, 3 Delavan HB 4 70° nozzles per row) with a CO2-pressurized system mounted on an IH 660 high clearance sprayer. Damaged bolls were counted Aug 22 and 27 as follows: 50 bollworm susceptible bolls were counted in each of the two center rows of each plot and the number damaged recorded. The two center rows of each plot were machine harvested Sep 19 and Oct 7. Damaged boll counts and yield data were subjected to analysis of variance and means separted by Duncan’s New Multiple Range Test where appropriate.
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