Order Lepidoptera: Family Noctuidae
Pest description and damage The variegated cutworm is commonly found in gardens in the PNW. The larvae are black with brown and white markings and measure 0.5 to 0.75 inch long. Damage includes leaf and shoot feeding and may include cutting plants off at the soil line. Cutworm larvae are nocturnal, and their damage easily confused with slugs, but cutworms make clean cuts, while slugs rasp from the side of the plant leaving a ragged edge. Cutworms leave pellet-shaped droppings, while slugs deposit S-shaped sludge wrapped in slime.
Biology and life cycle Cutworms are found throughout the year, but are most damaging early in the spring when overwintering larvae feed on emerging plant tissues. In the Pacific Northwest, small cutworms feed at night in mid-December and January. Larvae, or the shiny red-brown, bullet-shaped pupa case, also may be unearthed while weeding in spring and early summer. Eggs are laid in patches on plants or nearby grasses.
Pest monitoring Watch plants for fecal pellets near defoliated leaves by day or search plants for larvae at night in mid-winter in milder climates.
Several predators including ground beetles feed on cutworms and multiple wasps and flies parasitize them. Encourage natural enemies of cutworms like birds, ground beetles, and spiders. Ground scratching birds may also play a role in keeping numbers low.
Control weeds, grasses, and debris on the soil surface in the vegetable garden that provide cover for marauding larvae. Using a flashlight at night, remove cutworm larvae by hand picking. Sort through the loose soil at the base of plants to find larvae in the daytime.
See Table 2 in:
Chemical Control of Landscape Pests
For more information
Peterson, Merrill. 2012. PNW Moths (http://pnwmoths.biol.wwu.edu/browse/)
Rosetta, R. 2009. Cutworms. Oregon State University Nursery IPM (http://oregonstate.edu/dept/nurspest/cutworms.htm)