Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

First Advisor

Jerry B. Graves

Abstract

Growth, development and survival of pyrethroid-resistant (PY-R) and -susceptible (PY-S and FIELD-88) tobacco budworm, Heliothis virescens (F.), and bollworm (CORN-BW), Helicoverpa zea (Boddie), were compared on four cotton lines ('Deltapine 41', La. HG-660, La. HG-063 and PD-0804) and artificial diet. The FIELD-88 and CORN-BW strains had significantly higher 5 and 9 day larval weights compared to the PY-R and PY-S laboratory strains. Larvae fed squares of La. HG-660 and La. HG-063 had significantly lower larval and pupal weights, required significantly more days to pupate and had higher cumulative mortality compared to those reared on squares of a commercial cultivar, Deltapine 41. In a field trial conducted during 1988 to evaluate advanced cotton lines and insecticide treatments against tobacco budworm and bollworm, no significant interaction was observed. However, La. HG-660 reduced larval infestations and damage, matured earlier and had comparable yields to DPL 41. Lint turnout and boll weight was lower for La. HG-660 than that for Deltapine 41. No significant differences were found among treatments in fiber length, micronaire and fiber strength of cotton samples. The toxicity of insecticides to eggs of PY-R, PY-S and field (FIELD-89) tobacco budworm strains was determined in laboratory tests. LC$\sb{50}$'s for all insecticides except profenofos on eggs of the PY-R strain were significantly higher than LC$\sb{50}$'s for the same insecticide on eggs of the PY-S strain. All insecticides except profenofos and methomyl were significantly more toxic to eggs of the PY-S strain compared to their respective toxicity to eggs of the FIELD-89 strain. Eggs of the PY-R strain exhibited resistance to esfenvalerate, lambda-cyhalothrin, and chlordimeform while eggs of the FIELD-89 strain possessed resistance to lambda-cyhalothrin, chlordimeform and SN 49844. In field tests conducted during 1987-1989, all insecticide treatments except methomyl (0.0071 kg (AI) /ha) and profenofos (0.56 kg (AI) /ha) exhibited initial ovicidal activity in one or more trials. The formamidines (amitraz and SN 49844) and a carbamate (thiodicarb) at 0.28 kg (AI) /ha generally exhibited residual ovicidal activity comparable to that of chlordimeform at 0.28 kg (AI) /ha.

Pages

194

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