Alfalfa weevil is a problematic pest for alfalfa hay producers. Weevil larvae feed on alfalfa foliage in the early season, causing defoliation and reducing hay yields and quality. Currently producers use insecticides or early cutting practices to control this pest. Unfortunately these control methods can be costly or are not effective.
What about biological control? There have been major efforts by the Agricultural Research Service (ARS) and Animal and Plant Health Inspection Service (APHIS) to release several species of non-native parasitoid wasps throughout the US’s alfalfa growing regions, in an effort to control alfalfa weevil. Despite these efforts, weevil outbreaks continue to be variable and sometimes severe in Wyoming.
The overall goals of this study are to determine a.) which parasitoids are present in WY and to what extent are they controlling alfalfa weevil and b.) whether parasitoid populations are responding to alternative habitats at landscape or local scales. Alternative habitats can provide parasitoids with critical resources like nectar food sources and refuge from disturbances. If parasitoids are responding positively to these alternative resources, there is the potential for growers to adopt habitat management practices to help control their pest problems.
Preliminary Results 2014
In a survey of 10 alfalfa fields in southeastern WY (Platte and Goshen counties), we found parasitism rates of alfalfa weevil ranging from 7% – 34%.
Only one species of parasitoid wasp was recovered from these fields, Bathyplectes curculionis. This wasp was first introduced to control alfalfa weevil in 1911 in Utah and has since spread throughout WY.