Now that Fall has officially begun (Sept. 22nd), it’s time to start talking about potential for damage to fall and winter crops from Noctua pronuba, the winter cutworm.
According to limited data of N. pronuba activity in this region, there seem to be two flight periods – early spring (Mar-May) and now (Aug-Oct). Adult moths are easier to detect than larvae, and we are currently working on improving sampling techniques. Based on information from flight periods of adults, we can better estimate the potential for larval damage.
The widespread winter cutworm ‘epidemic’ of 2015 could have been one of two things: an unfortunate ecological fluke brought on by a combination of mild temperatures, moisture events, natural cyclical wave of predators, etc. or (gulp..) a sign of things to come.
We have found winter cutworm moths throughout the Valley and intend to increase sampling efforts over the next few weeks. Stay tuned and in the meantime, review these tips for scouting:
- If possible, examine plants at dusk, dawn, or preferably at night, when cutworms would be actively feeding. For daytime scouting, look in the soil at base of plants, digging up to 2″ may be required.
- Look for wide swaths of damage that may occur in a ‘feeding wave’ pattern – especially on large acreages. N. pronuba behaves like an armyworm, and true armyworm also has been noted in abundance this year. Click here to help distinguish between species.
- Larvae are large, and marked with black dashes down each side of the back. The dashes occur on the posterior 2/3rds of the body. A white to cream diagonal pattern may be present on the sides of the body, depending on how old the larvae is. The ventral (belly) side of winter cutworm may be tinged with pink.
- Adult moths are relatively large-bodied and have a unique coloration (see below). The orange-yellow hindwing is most noticeable if the moth is in flight; it ‘flashes’ out to the naked eye, as seen in this video: