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Agronomic Crops Network

Ohio State University Extension


Some Options for Organic Producers with Alfalfa Weevil

Alfalfa Weevil
We have been getting a number of reports about alfalfa weevil damage recently.  A recent newsletter article reviewed basic scouting and management advice (  However, organic producers face a particular challenge in managing this pest due to the limited number of products available for rescue treatment.  Potential options for Ohio organic producers are Pyganic (an organic pyrethrum) at 4.5 oz – 17 oz / acre and  Entrust (a spinosad) at the higher rate of 1.25 oz/acre.  We have not tested these products, but a University of California study found Entrust at the high rate to be moderately effective for alfalfa weevil control.  There is also a Bt product called beetleGONE! Ag ( that has shown some efficacy in a USDA-ARS trial in Montana.  If the weevil infestation is above the action threshold, we recommend treatment even with a high cost product. Why? In the past we have known organic alfalfa producers who lost most of their entire year’s crop as a result of weevil feeding in the spring. If weevil pressure is heavy, the first crop will be lost (unless it is cut before severe defoliation occurs).  The weevil can then survive on the stubble and feed on the crown buds, preventing the crop from regrowing, to the point where the stand never truly recovers during the summer.  Whether organic or not, producers should be careful and attentive to weevil infestations as severe damage can happen quickly.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.