Other regional agencies will be initiating a trapping program for this species and other armyworms. The presence of moths reported here are considered ‘non-target by-catch’ = the large yellow underwing moths (Noctua pronuba) were caught in pheromone traps deployed for other species in another program (OSU VegNet). Nevertheless, it has proven to be at least an indicator of timing over the past few years.
N. pronuba moths are easily recognized by their large size (2-3″ wingspan) and bright yellow-orange hindwing bordered by a thick black margin (FIG. 1). Review similar posts for more information about this species. Larvae behave as armyworms and can be active throughout the fall and winter.
…Over the past 2 weeks, I have started to detect Noctua pronuba in pheromone traps. There is a commercial lure available, and I have some of those deployed currently, but honestly, have just as good of luck tracking them as non-targets in other armyworm traps.
In 2017, there were 2 apparent activity periods, which matches with published estimates from U. of Idaho, one of the only other places in the country with a documented outbreak of winter cutworm. Click here to see an interactive comparison of trap catches between years, so far.
Keep in mind, these observations are NOT, at this time, part of a full-fledged sampling program for Noctua pronuba. Rather, I am mentioning adult flight because it is an indicator that there is POTENTIAL for winter cutworm activity starting about September 10th.
** Please review the OSU Extension publication for more info about host plants, history, biology, and identification of this species **.
This week, there were Noctua pronuba moths found in traps throughout the valley. Although we are not specifically trapping for them at this time, their presence should be considered a cautionary tale. As we know from years past, where there is one, there are many.
This moth is easily recognizable by 3 main features:
Large size (± 2 inch wingspan)
Bright yellow hindwing that can only be seen in flight
Thick black border on hindwing
Adult moths are not a problem. In fact, they have been in Oregon for 15 years. However, in 2015 there was an outbreak of larval N. pronuba, common name: WINTER CUTWORM. Yes, these larvae are active (hence feeding) throughout the fall and winter months. They move in groups, like armyworms, and can be very destructive.
Scroll down for more information on winter cutworm, or comment below if you have questions or concerns. Thanks for reading.
The arrival of Spring brings with it opportunity to discuss Noctua pronuba and its potential to affect this year’s plantings.
The extremely WET winter and recent mild temperatures mean that cutworm pressure could be higher than normal this year.
As seen in the figure below, crop damage can occur throughout the winter, AND ALSO INTO SPRING.
To scout for damage, look for areas of clipped grass or missing seedlings. Dig to at least 2″ and sort through the soil. Or, investigate at night to catch cutworms in the act!
Larvae will be feeding now, and they eat truly everything, including commercial grasses, home lawns, vegetable crops, and ornamentals. Most cutworms are subterranean but some can also climb up to feed on foliage. Certain species do this in vineyards, but until recently, we did not know if N. pronuba displayed this behavior:
Happy planting, and please feel free to CONTACT me with cutworm sightings or questions.
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:
Winter cutworm is a new pest threat in this region. It has a wide host range and can be very destructive because it moves and feeds in large masses, similar to armyworms. As the name implies, cutworms are active during the winter, and therefore can affect perennial and fall-seeded crops including legume and grass cover crops, grasses grown for seed, ornamentals, vegetables, and grains.
Between November 2015 and February 2016, dozens of reports were made throughout Oregon and Washington, where there was suspected damage from winter cutworm, which is the immature, damaging stage of the large yellow underwing moth. Adult moths have been present in this region since 2001, yet there had never before been accounts of widespread damage being done by winter cutworm. In response, an OSU Extension publication was released (availablehere), and public presentations were made in Multnomah, Polk, Linn, Benton, and Douglas counties.
Adult moths have been very abundant over the past few weeks. They are easily recognizable by their large size (~2″) and hindwing, which is bright orange-yellow and bordered by a thick dark band.
We are currently researching whether winter cutworm will be a problem again in the months to come.