By Jeff Bradshaw
Extension Entomology Specialist
As many of you know, Nebraska, and particularly western Nebraska, has had another mild dry winter and is expected to have a warm, dry spring. These conditions are conducive to the survival of some of the insects that overwinter in this region. One group of insects of particular importance are cutworms.
Although evenings are still cold, cutworms have been active during the past week. With warmer weather, cutworm activity will increase.
In western Nebraska, the most damaging cutworm is the army cutworm other cutworms such as the pale-western cutworm, dark-sided cutworm, and variegated cutworm also may cause damage. The army cutworm is the most destructive cutworm to crops including alfalfa, wheat, and sugarbeet as well as various rangeland grasses.
In late September and October, army cutworms lay 1,000 to 3,000 eggs directly on bare soil, such as in a new planting of winter wheat or heavily grazed patches of range. I
n the fall after a rain, eggs will hatch over an extended period. This results in a variety of sizes of caterpillars that will feed and develop as long as temperatures are adequate. Come April, large larvae can sometimes be abundant in winter wheat fields.
In 2011, moderate populations of the adult army cutworm moth (or “miller moth”) could be found in sheltered areas during the day.
These moths may have contributed to a larger population of larvae for 2012 and these high populations may continue for 2013. As we continue into March and April and wheat breaks dormancy, scout for cutworm activity.
Scouting and Thresholds
When scouting for army cutworms, use a treatment threshold of four or more cutworm larvae per square foot of winter wheat or alfalfa. However, for stressed, thin stands of wheat or for newly establish alfalfa stands, use a threshold of two or more larvae per square foot.
Thin, stressed stands or new stands of alfalfa require a lower threshold because they are more prone to cutworm damage.
Army cutworms only feed at night and seek out dark sheltered areas during the day so turn over clods of loose soil and residue for accurate cutworm counts.
If army cutworm counts are above threshold, you may want to consider an insecticide application. Always read pesticide instructions carefully before use.