Author
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CHARLET, LAURENCE |
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Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/14/2003 Publication Date: 10/1/2002 Citation: CHARLET, L.D. SUNFLOWER BEETLE (COLEOPTERA: CHRYSOMELIDAE) OVIPOSITION, OVERWINTERING, AND IMPACT OF CULTIVATION ON ADULT SURVIVAL IN CULTIVATED SUNFLOWER. JOURNAL OF AGRICULTURAL AND URBAN ENTOMOLOGY. OCT 2002. V. 19 (4). P. 185-195. Interpretive Summary: The sunflower beetle is the most damaging defoliator of sunflower in North America. Studies were conducted from 1995 to 1997 in North Dakota, to determine beetle egg laying period, number of eggs laid, and adult longevity in the laboratory, viability of field laid eggs, with-in field location and soil depth of overwintering adults, and impact of cultivation as a management tactic to reduce beetle numbers. Females laid eggs over a period of 39 - 60 days. An average of 90, 438, and 854 eggs per female were laid in 1995, 1996, and 1997, respectively. Total production ranged from 15 - 1981 eggs per female and over 70% hatched each year. The number of eggs laid per female per day increased from 2.3 in 1995 to over 14 in 1997. Males survived 44 days in 1995 and 99 days in 1997, females 49 days in 1995 and 86 days in 1997. Percentage egg survival in the field increased from mid to late June 1995, primarily due to a reduction in shriveled eggs. In 1996, results were reversed and in 1997, viability was high and no difference was noted in collection dates. A combination of infertility, weather and predation could explain the different percentage of shriveled eggs between the intervals when eggs were recovered. Soil samples recovered in both spring and fall during 1996 and 1997, showed that adults move into the soil directly under the sunflower plants to overwinter. There was no differences among the different soil levels in which sunflower beetle adults were sampled, but there was an indication that adults move up in the soil in the spring prior to emergence. Neither fall nor spring tillage affected emergence of adults. Thus, disturbing adults by tilling the field either in the fall or spring does not have a negative impact on overwintering sunflower beetles in the soil. Technical Abstract: The sunflower beetle, Zygogramma exclamationis (Fitch) is the most damaging defoliator of sunflower in North America. Studies were conducted from 1995 to 1997 in North Dakota, to determine sunflower beetle oviposition period, fecundity, and adult longevity in the laboratory, viability of field laid eggs, with-in field location and soil depth of overwintering adults, and impact of cultivation as a management tactic to reduce beetle numbers. Females oviposited over a period of 39 - 60 days. An average of 90, 438, and 854 eggs per female were laid in 1995, 1996, and 1997, respectively. Total production ranged from 15 - 1981 eggs per female and over 70% hatched each year. The number of eggs laid per female per day increased from 2.3 in 1995 to over 14 in 1997. Males survived 44 d in 1995 and 99 d in 1997, females 49 d in 1995 and 86 d in 1997 (range 19 to 163 d for males; 14 to 167d for females). Percentage egg survival in the field increased from mid to late June 1995, primarily due to a reduction in shriveled eggs. In 1996, results were reversed and in 1997, viability was high and no difference was noted in collection dates. A combination of infertility, weather and predation could explain the different percentage of shriveled eggs between the intervals when eggs were recovered. Soil samples recovered in both spring and fall during 1996 and 1997, showed that adults move into the soil directly under the sunflower plants to overwinter. Data did not show significant differences among the different soil levels in which sunflower beetle adults were sampled, but there was an indication that adults move up in the soil in the spring prior to emergence. Neither fall nor spring tillage affected emergence of adults. Thus, disturbing adults by tilling the field either in the fall or spring does not have a negative impact on overwintering sunflower beetles in the soil. |
