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" Evaluation of natural enemies associated with the millet stalk borer, Haimbachia ignefusalis (Hampson) (Lepidoptera: "
O. Youm
F. E. Gilstrap
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Latin Dissertation
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English
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| Record Number
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1112640
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TLpq303920780
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| Main Entry
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F. E. Gilstrap
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O. Youm
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| Title & Author
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Evaluation of natural enemies associated with the millet stalk borer, Haimbachia ignefusalis (Hampson) (Lepidoptera:\ O. YoumF. E. Gilstrap
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| College
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Texas A&M University
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| Date
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1990
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| student score
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1990
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| Degree
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Ph.D.
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| Page No
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160
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| Abstract
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Studies conducted from 1986 through 1988 on the millet stalk borer (MSB), Haimbachia ignefusalis (Lepidoptera: Pyralidae) included investigations on its host plants, natural enemies, oviposition behavior, effects on crop loss, survival as diapausing larvae in excised millet stalks, and population dynamics. Population dynamics were described for Sesamia calamistis Hampson and the millet head girdler (MHG), Heliocheilus albipunctella de Joannis (Lepidoptera: Noctuidae). Effects of planting dates on population densities of MSB and MHG were assessed. Life-fertility tables were described for Bracon hebetor Say (Hymenoptera: Braconidae). MSB was collected from fourteen alternate host plants and was parasitized by a complex of parasite species on millet and seven of the alternate host plants. A model describing interactions between MSB, host plants, and natural enemies is proposed. Mean numbers of surviving MSB in field cages excluding natural enemies were not significantly different from mean numbers of MSB that survived in field cages where natural enemies had access. These results suggest that natural enemies did not control MSB on millet. MSB oviposition was mostly associated with green millet stalks with leaf sheaths, leaf sheaths being the most preferred oviposition sites. Millet grain weight was negatively correlated with numbers of MSB larva holes. Numbers of diapausing MSB larvae and MSB larva holes increased from lower to upper stalk internodes. Many diapausing MSB larvae died during the dry season; however, a substantial number survived due to the stacking of millet stalks. MSB population densities were not reduced by adjusting millet planting dates, but were affected by millet growth stage. Platytelenomus sp. (Hymenoptera: Scelionidae) was the most common parasite of MSB on millet. Parasitism of MSB larvae and pupae was rare. S. calamistis was a minor pest of millet in Niger, and was rarely parasitized. MHG population densities were reduced by delaying millet planting dates. Bracon hebetor was the most common parasite of MHG. Life-fertility tables for B. hebetor developing on MHG showed that on the average, mated parasite females lived 24.7 days, oviposited for 22 days, and produced 173.7 adult progeny with a ca. 1:1 sex ratio. The estimated innate capacity of increase (usdr\sb{\rm c}usd) and net reproductive rate (Ro) were 0.26 and 86.5, respectively. The mean generation time was 17 days.
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Biological sciences
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Ecology
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Entomology
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Entomology
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