Sainfoin Trial to Evaluate Solutions for Alfalfa Weevil Damage

Published: 2020
By Michael Schuldt

Cropping practices to produce alfalfa hay in Southeast Montana are promoting high populations of Alfalfa Weevils. The standard management practice is to scout the fields and utilize a broad-spectrum insecticide to prevent economic damage from this pest. Resistance by the weevil to available insecticides has been identified, and the need for an alternate management strategy is imminent. Crop rotation is a tool commonly used for insect management, and sainfoin is a potential legume rotation for alfalfa acres. Sainfoin has similar production capability with comparable forage quality to alfalfa. Weevils do not impact this crop and it has the additional benefit of being a non-bloat species for livestock grazing. To analyze the potential of sainfoin, in May 2020, three one-acre irrigated plots were seeded to three varieties of sainfoin. The goal of the trial is three-fold: demonstrate sainfoin as a legume, irrigated, rotational crop for this region; evaluate varietal differences for our conditions; and develop weed management/control recommendations. Although we have adequate stand establishment with all three varieties, weeds pressure from weed seeds introduced with T & Y irrigation water is a concern. Although sainfoin is not a Round-up Ready crop, there are reports of natural resistance to this chemistry. Trial plots were established in October to apply three rates, 12, 22 and 44 ounces of glyphosate. Evaluation for damage to sainfoin plants is on-going with plans to apply an appropriate rate in spring. Production data will be collected for forage harvest. Incorporating sainfoin as a rotational crop in just the T&Y irrigation district has a potentially large economic impact. There are 6,305 irrigated hay acres that commonly receive at least one insecticide application annually. Cost of application and product averages $16/acre. Rotation to sainfoin to reduce insecticide application in 1/3 of the acres would result in less chemical impact and cost saving of $33,500 annually for growers in the irrigation district.