By the time corn begins to emerge in late spring, growers may already have battled varying weather elements and difficult planting conditions, but now it may be time for them to start battling another of Mother Nature’s surprises — cutworms.
These small insects — named for their ability to cut down plants — can wreak havoc on seedlings just a few weeks after seeds sprout. While seed treatments stave off damage from fungus and insects that feed below the soil surface, cutworms feed on the foliage and stalk of corn seedlings.
Several varieties of cutworms exist, including black, bronzed, variegated, dingy, glassy and army cutworms. However, most cutworms don’t overwinter in the Midwest. Instead, in early spring, adult cutworm moths migrate north from warmer climates and lay eggs in moist areas of a field or on broadleaf plants. Those cutworm caterpillars feed off the new vegetation of emerging corn seedlings. In fact, they can begin feeding within seven days after emergence. If a field has a high population of cutworms, plant stand could be compromised as the cutworms grow large enough to eat corn stalks from the base.
Growers could have a difficult time spotting cutworms until damage is visible, but early scouting could prevent stand loss. Scouting should start as soon as plants begin to emerge and continue each week until the seedlings reach the V5 leaf stage.
Cutworm caterpillars are nocturnal and hide during the day. Growers would need to scout corn plants for signs of feeding either on the leaves, around the base of the stalk or in the soil next to cut plants. Look under soil clods or in loose soil for cutworm caterpillars about 1 inch or less in length. Unfortunately, cutworms are often the same color as soil with brownish or black bodies, so you’ll need to have a focused eye while scouting. When disturbed, the caterpillars may roll up in defense, but you can still identify them by their distinct head and three pairs of front legs. They also have fleshy, stub-like prolegs along their abdomen.
Scouting can help growers identify the presence of cutworms, but there are efforts growers can take before plants emerge. Corn seed with Bt trait packages, such as Stine Agrisure® Viptera® and Agrisure Duracade® brand corn can offer some suppression of cutworm. Although helpful in mitigating cutworm, Viptera and Duracade treated corn must be ingested by the cutworm for it to die, so it’s more of a reactive treatment to suppress the pest.
Additionally, weed control can help reduce the presence of cutworms as the larvae can develop better on some weed species. If growers till or spread pre-emergent treatments for weeds before planting, cutworms may starve before plants emerge.
If farmers are noticing cutting on three to five percent of plants, it’s time for a post-emergence insecticide treatment. Always read and follow label directions before applying an insecticide.
For more information on cutworms and how growers can prevent them from impacting yields, contact your local Stine sales agronomist.