Author
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CHARLET, LAURENCE |
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Submitted to: Great Plains Sunflower Insect Workshop Proceedings
Publication Type: Proceedings Publication Acceptance Date: 9/15/2000 Publication Date: N/A Citation: N/A Interpretive Summary: The incidence, degree of infestation, and amount of damage caused by the sunflower midge has been quite sporadic since it was first reported as a pest in 1971. The history of damage by this pest is reviewed from 1971 to 1999. The sunflower midge overwinters in the soil as a mature larva, pupating in June. Adults of the overwintering generation of midge emerge from the soil in early to mid-July, mate, and live for about 2-3 days. Females oviposit in sunflower buds. The larvae are white and develop through three instars. After hatching, the newly emerged larvae move to the base of the bracts and feed, producing necrotic feeding depressions. The feeding by the larvae within the head results in head distortion or growth deformity likely from elevated levels of phytohormones. The mature larvae drop to the soil and complete development or remain as larvae and overwinter until the following year. Approximately 90% of the overwintering generation of larvae have completed development and move into the soil by early August. The life cycle of the midge that emerge the same season as first generation adults takes about a month. By late August 90% of these first generation adults have emerged from the soil. After larval development is complete they drop to the soil to overwinter with the majority exiting the sunflower heads by mid-September. The first generation midge, which attack sunflowers in the middle of the season, cause less severe damage because heads have already developed and seeds are filling and maturing. Technical Abstract: The incidence, degree of infestation, and amount of damage caused by the sunflower midge has been quite sporadic since it was first reported as a pest in 1971. The history of damage by this pest is reviewed from 1971 to 1999. The sunflower midge overwinters in the soil as a mature larva, pupating in June. Adults of the overwintering generation of midge emerge from the soil in early to mid-July, mate, and live for about 2-3 days. Females oviposit in sunflower buds. The larvae are white and develop through three instars. After hatching, the newly emerged larvae move to the base of the bracts and feed, producing necrotic feeding depressions. The feeding by the larvae within the head results in head distortion or growth deformity likely from elevated levels of phytohormones. The mature larvae drop to the soil and complete development or remain as larvae and overwinter until the following year. Approximately 90% of the overwintering generation of larvae have completed development and move into the soil by early August. The life cycle of the midge that emerge the same season as first generation adults takes about a month. By late August 90% of these first generation adults have emerged from the soil. After larval development is complete they drop to the soil to overwinter with the majority exiting the sunflower heads by mid-September. The first generation midge, which attack sunflowers in the middle of the season, cause less severe damage because heads have already developed and seeds are filling and maturing. |
