Control of Pink Bollworm with Growth Regulators, 1979-80

Abstract

Abstract Field plot tests were conducted with combinations of Coax and Thompson-Hayward diflubenzuron for control of the pink bollworm in fields of short staple cotton on the Cotton Research Center, Maricopa Co, AZ. In 1979 we tested a single treatment consisting of 1.15 kg AI of diflubenzuron plus 2.30 kg of Coax at a rate of 1200 1 of water/ha. This rate of Coax was the minimum label rate and the rate of diflubenzuron was well above levels normally used for control of leaf feeding Lepidoptera. Six weekly applications were made during the period Jul 30 - Sep 4. During the 1980 season we tested 3 treatments (1) 1.15 kg AI diflubenzuron, (2) 1.15 kg AI diflubenzuron plus 11.5 kg Coax, and (3) 1.15 kg AI diflubenzuron plus 11.5 kg Coax plus 2.5% additive. All treatments were applied at a rate of 94 1 water/ha. The additive was composed of solvent extracts of cottonseed and was tested as an additional specific feeding stimulant for the pink bollworm. In this test, the rate of application of Coax was the maximum label rate and the water was reduced from the 1979 test to thicken the mixture. We made 9 weekly applications during the period Jul 14 - Aug 25. Two of these applications were repeated after heavy rain. The test plots were placed in cotton that received usual cultivation and irrigation treatments, but no insecticides were applied. The effects of the treatments on populations of the pink bollworm were determined by collecting samples of 25 firm green bolls (ca 14-20 days oldj from each plot on a 7-10 day schedule during the periods of treatment. The boll samples were incubated in the laboratory at 27°C and 30% R.H. in ventilated plastic boxes. After 2 wk the numbers of larvae, pupae, and adults were counted and recorded. We also surveyed 10 plant terminals/plot each wk for Heliothis oviposition during these tests. All tests used plots 4 rows x 7.6 m (100 row ft) and all treatments were replicated 3 times in a randomized block design. The test materials were applied using 7.5 1 pressurized hand-held sprayers with the intent of obtaining thorough coverage of all plant surfaces. Analysis of variance was used to test for significant differences (P = 0.05) in treatment means.