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)
  • Cereals
  • Corn
  • 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).

Glassy cutworms have reddish-brown heads and a darkened plate just behind the head.

MANAGEMENT
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.
  • 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)

 

Adult moths have a busy forewing pattern and can be worn beyond recognition. Look for black triangles near the terminal edge of the forewing, and a kidney-shaped (reniform) spot outlined in white. Hindwings have a gray border and white fringe.