Alfalfa Snout Beetle: A Small Bug Creating a Huge Problem

Alfalfa snout beetle (Otiorhynchus ligustici) is an insect pest of perennial legumes and hops. It is a native of Europe and was first detected in New York in 1896. This pest is also highly destructive to alfalfa and clover.
( Gyorgy Csoka, Hungary Forest Research Institute )

The alfalfa snout beetle has been wreaking havoc on alfalfa crops since alfalfa was first introduced as forage for the dairy industry in the 1920s. Currently, this destructive pest infests more than 500,000 acres throughout nine Northern New York counties and into a small portion of Ontario, Canada right across the St. Lawrence River. A report done by Cornell Cooperative Extension estimates that the damage sustained to the alfalfa can cost a farmer up to $381 per acre, depending on the cut system in place and the extent of the damage. In addition, there are a number of other indirect costs that are not even accounted for in that $381 per acre, such as: increased purchases of off-farm protein sources, increased cost of milk production, the larger harvest equipment and increased acreage required to grow a quality grass forage as opposed to alfalfa, and the impact on a farm’s already in place nutrient management plan.

Unfortunately, due to the nature of the snout beetle’s life cycle and the timing of the destructive feeding behavior, infestations are not always identified. In early summer, a single snout beetle will lay up to 500 eggs in the soil. It is the resulting larvae that feed on the alfalfa roots from mid summer into late fall. Major plant injury and resultant death does not usually occur until after the final harvest of the year, allowing the damage to go unnoticed until spring and be attributed to winter kill, rather than from a pest infestation. In the past, once a field was infested with the alfalfa snout beetle, the alfalfa stand was doomed and neighboring farms could only cross their fingers and hope the beetle did not find its way to their alfalfa fields. Some growers were even forced to grow only grass hay on their fields. The use of poison baits was enlisted from the 1940s through the early 1970s and was effective in controlling the spread of the snout beetle, but was discontinued due to environmental concerns. Insecticides applied to alfalfa fields was tried and found to be ineffective. Without a chemical option to control snout beetle infestations, the only remaining management strategy was to intensively rotate alfalfa crops. However, this strategy could only be effective with a coordinated community effort that was too difficult to implement and maintain. Thus the snout beetle continued to spread and the number of infested acres continued to enlarge. With alfalfa being a staple in most dairy cow rations, it was clear that a solution was needed.

In the early 1990s, Dr. Elson Shields discovered potential biological control organisms, insectattacking microscopic worms (EPNs or nematodes), that were able to successfully reduce the amount of snout beetles present by 90-94% and reduce alfalfa stand loss to only 15%, as opposed to the 100% stand loss that was occurring before. Since then, research has continued and focused on persistence of the nematodes in the harsh northern New York climate and application techniques, including timing and dose rates, to maximize their effects on snout beetle populations while decreasing the cost to the farmer. Currently, the application of nematodes runs between $10-$20 per acre, depending on whether the nematodes are reared by the farmer or purchased from Cornell University. Although the nematodes can get expensive as the number of acres increases, they are a much more viable option than suffering the losses from a damaged alfalfa stand. With the snout beetle continuing to migrate, it might not be a bad idea to get ahead of the infestation and start looking into nematodes now.