…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 **.
AUGUST 2018 – EDITS to the original (FEB 2018) post
Ok, now that I’ve got your attention…
The subject line is a playful way to introduce you to Apamea devastator, although the damage it can do is no laughing matter.
This species overwinters as mature larvae, and I found some south of Corvallis just last week.
Larvae live underground, and feed on roots and the base of plant stems.
Host plants include:
Grass (pasture and seed)
In outbreak years, feeding has been reported on: cabbage, lettuce, bean, beets, and radish
This pest is particularly fond of fescue, timothy, and bluegrass. Outbreaks have occurred in PNW fescue.
SCOUT IN SEPTEMBER AND OCTOBER by surveying grass fields for any sign of browning-off or slow growth. In herbaceous plants, the first sign of injury is often WILTING. Dig up the roots and search surrounding soil for translucent, large (3cm), greenish to white larvae with little to no body markings, except for the brown prothoracic shield just behind the head. Common name: glassy cutworm refers to the light, almost ‘glassy’ appearance, versus most other cutworms that have distinctive markings along the surface of the body (examples here).
It is important to realize that general predators can keep cutworms populations suppressed below damaging levels. Parasitoid pressure, however, may not be as effective for this species; a 1990 study from Oregon found that the cutworms matured almost to pupation before they were killed by parasitoids, thus feeding in the current season is not suppressed. Try to consider the impact on natural enemies before choosing to apply chemical controls.
If scouting reveals a need to make a treatment, consult the PNW Insect Management Handbook, and be sure your crop is listed on the pesticide label. Rain or irrigation may help move the product into the soil surface, which is important for this species.
TIPS FROM THE FIELD/LITERATURE:
This year (2018), I am catching A. devastator adult moths as non-targets in traps placed near cole crops. This could mean they are emerging from fields where they did early-season damage as larvae – because they feed on roots and stems, perhaps this is one of the factors contributing to the broccoli mystery. It also suggests that actual population numbers are higher than normal, because I usually do not see this species in my traps.
In fine fescue, damage from larvae tends to occur more on plants that are within 3 ft of a weedy grass.
In western Oregon, glassy cutworm (Apamea devastator) moths emerge in late June, peak in July, and larvae take 100-120 days to develop, depending on daylength
A. devastator has dangerous similarities to Noctua pronuba, the winter cutworm: both species have erratic outbreaks, and have caused damage to Oregon crops in previous years. Both overwinter as larvae, and have been documented feeding throughout the fall and winter. (E.G. THIS ORIGINAL POST – FEB 8th, 2018)
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.