Weed Control News

Improving Establishment of Flea Beetles on Leafy Spurge

Leafy spurge is a noxious perennial weed that occurs as isolated infestations covering nearly 5 million acres in the northcentral United States and Canada. Four species of flea beetle have been introduced from Europe for biological suppression of leafy spurge. Flea beetle larvae damage leafy spurge plants by feeding on roots and interfering with water and nutrient uptake. After emergence, adults congregate on leafy spurge foliage to feed and mate.

Black dot flea beetles (Aphthona nigriscutis) have become established at a leafy spurge-infested site near Pollack, South Dakota, where approximately 40,000 beetles have been collected annually for redistribution to other areas in the state. However, little was known about the reproductive viability of the beetles collected and released.

Following flea beetle emergence in 1995, adults were collected weekly over a 6 week period with sweep nets. Sex ratios, and percentage of mated females were determined to evaluate the reproductive status of black dot flea beetles. Males constituted only 4% of adults in samples. The percentage of mated females increased to 44% approximately 3 weeks following adult emergence, and then declined.

Results from the 1995 study suggest that the reproductive status of black dot flea beetles should be monitored prior to collection for redistribution. Collections taken too early or late in the summer season may contain low percentages of mated females and few males. By monitoring the reproductive status of black dot flea beetles, the potential for establishment success in new areas might be improved.

- Mark A. Brinkman and Sharon A. Clay, South Dakota State University and Jan J. Jackson, USDA-ARS, Brookings, South Dakota

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