Alfalfa Snout Beetle Update

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 )

Alfalfa snout beetle (ASB) is a major insect pest of alfalfa fields in northern New York. Arriving on ships in 1896 from Europe, ASB is thought to have entered NY through the port of Oswego. In 1933 ASB was found in multiple alfalfa fields and has since spread to all northern NY counties. Jefferson, St. Lawrence, and Lewis counties have experienced the most ASB pressure by far, however Essex, Clinton, and Franklin counties have areas where ASB is active.

ASB is a soil-dwelling insect and spends most all its time as a larva and adult underground. For this reason, insecticides are not a viable option for control. ASB also has a wide host range of plants that it can use for food other than alfalfa, including weeds and clovers.

On March 28 Cornell Cooperative Extension of Clinton County held a meeting to discuss ASB and the latest management options for minimizing damage from this pest. Dr. Elson Shields, Cornell Professor of Entomology, has spent nearly 30 years researching ASB and potential options for management. He spoke at the meeting to a small group of farmers and consultants summarizing his ASB research findings and recommendations.

ASB is costly for those dairy farms that have it. Based on estimates from agronomists and nutritionists, damage from ASB could cost $200 to $500/acre depending on how quickly it eliminates an alfalfa stand. Much of the cost comes from having to purchase soybean meal to replace the lost protein in the ration. Actual costs of ASB depend on several farm-specific factors including the amount of alfalfa grown, degree of damage, amount fed in the ration, and crude protein content of forages. Based on the amount of extra soybean meal needed and assuming a 100-cow dairy, costs could range from $4,000 to as high as $20,000/year (estimates provided by Michael Miller and Ev Thomas).

Through his many years of research, Dr. Shields has developed an effective strategy for managing ASB that involves the use of nematodes as ‘biocontrol’ agents. Nematodes are soil dwelling round worms that some consider the most numerous animal on Earth. Many nematodes are parasitic and use grubs and other insects as hosts. Entomopathogenic nematodes specifically target insects as hosts, and it is this group that is effective at controlling ASB. Dr. Shields’ work shows that biocontrol nematodes can be applied at a low cost and that populations can quickly increase (a couple of years) to the point where ASB pressure is reduced. This translates to having the chance for a 4 or 5-yr alfalfa stand instead of a 2-yr stand. The nematodes are native to northern NY and appear to maintain populations into a corn rotation and beyond. More good news is that the nematodes also appear to help control corn rootworm, white grubs, and wire worms.

Dr. Shields’ lab has reared biocontrol nematodes for their research program for decades. Now that the research has proven effective in the field, there is a greater need for commercial nematode application. Mary DeBeer (DeBeer Seeds & Spraying, Moira, NY) has worked closely with Dr. Shields over the past five years and has developed a nematode-rearing business as part of their existing seed and custom spray operation. DeBeer’s offer nematodes for application in addition to custom applying nematodes. Mary said the cost is $26/acre to purchase nematodes for application. While ASB- resistant alfalfa developed at Cornell also helps reduce risk of ASB damage, nematode application appears to be the best option available for controlling ASB. Dr. Shields recommends using biocontrol nematodes and ASBresistant alfalfa together where ASB pressure is high.

 
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