Management:
The alfalfa snout beetle was introduced into North America from Europe during the 1800’s in shipping ballast and was first introduced in the Port of Oswego, NY. When alfalfa was introduced into Oswego Co in the 1920’s, snout beetle became a significant pest almost immediately and was throughout 3000 acres. Today, this insect infests more than 500,000 acres in 9 NY counties and remains a very severe pest of alfalfa.
Management of this insect remains a challenge with alfalfa stands often being killed out in a single year. Life history and behavior of this insect limits the effectiveness of insecticides and they are not recommended under any circumstance.
Crop Rotation:
Beetle populations on a farm can be managed and kept to a reasonable level by limiting alfalfa stand life to only 3 years. Simply adding a 4th year to the stand allows the beetle population to explode to very high levels. The 3 years are considered the seeding year and 2 production years. Then the stand is plowed down and planted to a non-host (corn or soybeans) for at least 2 years. When effective rotation is used, farmers are required to plow down an economically viable alfalfa stand and few farmers are willing to do so. As a result, rotation is never been an effective management tool.
Biological Control:
During the past 15 years, research has shown that biological control with entomopathogenic (insect-attacking) nematodes has potential and is effective in reducing snout beetle populations to sub-economic levels in alfalfa fields where the native NY adapted nematodes have been established. Currently active extension programs are focused on teaching farmers to rear and apply these nematodes to their own infested fields. Farmers interested in participating in the program should contact their local Cooperative Extension Office. A continuing research effort is focused on identifying key factors to enhance nematode persistence and efficacy.
Resistant Alfalfa:
For the past 15 years, an intense effort has been focused on the identification of potential resistance in alfalfa to snout beetle larval root feeding. This research has been a collaboration between the Cornell Forage Breeding Program led by Dr. Don Viands and the alfalfa snout beetle research effort led by Dr. Elson Shields. To date, more than 235,000 seedlings have been screened for snout beetle larval resistance in the greenhouse, promising plants intercrossed and promising experimental lines tested in the field against snout beetle populations. Field results are very promising and the first variety with moderate resistance, Seedway 9558 SBR, is now available to producers. Field trials to test unselected populations against select populations in snout beetle infested land have allowed researchers to observe significant increases in yield and a reduction in root feeding damage. Results of several field experiments show progress is being accomplished in selection for alfalfa with resistance to snout beetle feeding damage. Our goal is to continue development of resistant varieties that have high resistance to alfalfa snout beetle damage. We believe that higher levels of resistance are achievable and would provide more effective control in the long term. Resistant varieties in combination with nematodes that reduce snout beetle populations is the best control option for producers.
To see results from two field trials testing unselected populations against select populations, Click Here.
Current Management Recommendations:
We believe both biological control with biocontrol nematodes and the planting of resistant alfalfa varieties will be required to effectively reduce the alfalfa snout beetle populations to sub-economic levels. Biological control nematodes are required to reduce the very large populations to a lower level and resistance alfalfa will be required to maintain the insect at the lower sub-economic level.
Alfalfa Stand Age: We recommend that bio-control nematodes should be applied on alfalfa fields in their seeding year, or 1st production year for the best economic impact. If biocontrol nematodes are focused on this age of fields each year, the entire farm will be treated within 3-5 years and the cost of treatment can be spread out over the same time period. However, if farmers chose to apply biocontrol nematodes to more established alfalfa fields, the biocontrol nematodes will establish and attack snout beetle larvae present, but will not assist with stand retention of the alfalfa stand.
Application Timing: Since the biocontrol nematodes need to be applied to the soil surface but have some shading from sunlight until they enter the soil, we recommend that the applications be made to alfalfa fields 2-3 weeks after harvest. This allows about 6″ of regrowth which shades the soils surface while allowing the stream of water from the sprayer to easily contact the soil surface. In addition, applications should be made late in the day (after 6 pm) or during cloudy and/or rainy days to minimize nematode death from intense UV sunlight. Applications need to be made before September 1st.
Nozzle Spacing: Nematodes will be applied using the “skip nozzle” method, leaving every third nozzle open and nematodes will be applied to 33% of the acreage driven over by the application equipment (based on nozzle separation of 22-24”).
For additional information on bio-control nematode application techniques go to Biological Control