Timing applications of plant growth regulators and last irrigation for pink bollworm (Lepidoptera: Gelechiidae) control
Bariola, L.A. | Chu, C.C. | Henneberry, T.J.
After ethephon and thidiazuron were applied in late season to small plots of Upland cotton (Gossypium hirsutum L.) to terminate fruiting chemically, the numbers of green bolls and pink bollworm, Pectinophora gossypiella (Saunders), diapausing larval populations, and yields were determined. Tests were conducted during 1985 and 1986 on the Maricopa Agricultural Center, Maricopa, Ariz., and on the Irrigated Desert Research Station, Brawley, Calif. Also, at Brawley in both years, we determined the combined effects of early irrigation cut-off and chemical termination. Results show that rates of 1.12 kg (AI)/ha of ethephon or higher and rates of 0.056 or 0.112 kg (AI)/ha of thidiazuron were needed for effective termination of cotton fruiting as indicated by reductions in number of green bolls. These rates of each chemical also reduced the number of squares and blooms after treatment, and sequential applications resulted in greater reductions than a single application. Last irrigation in mid-July resulted in reduced yields. However, irrigation cut-off in late July or early August resulted in yields as high as when the last irrigation was in September. Yields were not reduced by chemical termination treatments except by thidiazuron at Brawley in 1986, when last irrigation was in mid-July. Diapausing pink bollworm larval populations were reduced by chemical termination treatments and early irrigation termination.
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