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Cutworms

When looking for cutworm feeding in emerging sunflower early damage is usually found on south facing slopes or areas where the soil tends to warm up quickly. The difficulty with this insect is scouting due to night-time feeding. Thus, entomologists recommend an evening insecticide application. The NDSU recommended threshold level is 1 larva per square foot. For more detail see the April 2010 story on Cutworm Vigilance in The Sunflower magazine. There are many different species of cutworm. The various sunflower production guidebooks mention these species as damaging to sunflower: Army Cutworm (Euxoa auxiliaris) Manitoba Redbacked Cutworm (Euxoa ochrogaster) Manitoba and North Dakota Darksided Cutworm (Euxoa messoria) North Dakota and High Plains Dingy Cutworm (Feltia jaculifera) North Dakota and High Plains Pale Western (Agrotis orthogonia) High Plains Sandhill (Euxoa detersa) High Plains Each species has special identifiable features. See the pictures or go to the Guidebooks listed below for more information. Damage has been significant in some years and replanting has been required. Reduced tillage appears to result in greater numbers.

Life Cycle: Depending on the species, the adult lays eggs in the soil in the late summer. Eggs remain dormant until the May/June period. Damage: Cutworms usually damage the young plants by cutting them off below or above the soil surface. This generally occurs in early emergence. Cutworms feed mostly at night and rest during the day below the soil surface near recently damaged plants. Economic Thresholds: One larvae per square foot or there is a 25% to 30% stand reduction observed. Scouting Method:Check fields at least twice a week during early emergence looking for cutoff plants or digging around a damaged plant to determine if cutworms are present. One producer uses a sprayer mounted on a four wheeler. He sprays an X pattern in the field with a labeled insecticide and later counts dead cutworms. Management: Most of the commercial insecticides labeled on sunflower include cutworm as well. This works well for surface feeding cutworms. A number of producers in reduced tillage systems now calculate a cutworm insecticide treatment in their budgets. Control is done at emergence or just prior. It is important to note that insecticide seed treatments are not labeled to control cutworms in sunflower. Research: There is limited research being done on cutworm in sunflower. Photos: Visit the Photo Gallery. View the Insect section in the Archive section of The Sunflower magazine. Source: NDSU Extension Bulletin 25 Sunflower Production Handbook, NDSU Extension Service, September 2007, High Plains Production Handbook June 2005 and the Sunflower Production Guide, Manitoba.

High Plains Sunflower Production Handbook  file size: 1554 kb

NDSU Extension Bulletin 25 - Revised 9/2007 file size: 5591 kb