Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2004
Publication Date: 9/15/2004
Citation: Blodgett, S.L., Lenssen, A.W. 2004. Distribution of alfalfa weevil (coleoptera: curculionidae) larvae among post-cutting locations. Journal of Economic Entomology. 97(4):1319-1322. Interpretive Summary: Numerous cultural control methods for alfalfa weevil have been investigated, including early harvest. However, studies of early harvest have not been done with modern haying equipment. In field trials, we found that mortality of alfalfa weevil larvae in standing alfalfa was minimal due to cutting and crimping. Alfalfa weevil larvae in swathed alfalfa forage decreased as the forage became drier, and at the same time, larval populations increased in stubble under and between windrows. The effectiveness of alfalfa weevil control by early harvest can be substantially improved by conservation of swathed alfalfa forage as silage, bale silage or high moisture hay compared to baling at conventional moisture levels. Conservation of alfalfa forage at higher moisture levels allows for increased removal rates of alfalfa weevil larvae preventing damage to crop regrowth without the use of an insecticide treatment.
Technical Abstract: A field study was conducted in 1996 and 1997 to determine survival and spatial patterns of alfalfa weevil larvae (Hypera postica (Gyllenhal)) within and between windrows of swathed alfalfa (Medicago sativa L.) forage as dry matter concentration increased. Following harvest, the percentage of live weevil larvae residing in swathed forage decreased as swath dry matter percentage increased. Conversely, larval populations in stubble between windrows increased with increasing swath dry matter. Larval populations in stubble under windrowed forage increased slightly as windrowed forage dry matter increased. Applications of these results for the development of alfalfa harvest systems for improved cultural control of alfalfa weevil are discussed.