Winter Cutworm, Snow Cutworms, Large Yellow Underwing, Large Yellow Underwing, Common Yellow Underwing Moth, Cutworm, Winter Cutworms, Snow Cutworms
Noctua pronuba, or the Yellow Underwing, is named after the brightly coloured hindwings. They belong to the largest family of moths, called Noctuidae. The caterpillars are named cutworms, because they damage plants by chewing through the stems, cutting them at the base. The caterpillars of N. pronuba have been recorded on numerous herbaceous and ornamental plants, as well as vegetables like Brassicas and Alliums. In some years they can be quite destructive. The main symptoms involve chewed leaves, buds and stems. Cutworms sometimes attack the roots of plants, too. As adults, moths are important pollinators. Likewise, moths play an essential role in the food chain, preyed heavily upon by bats and birds.
Will attack plant foliage as caterpillars.
These moths can help support bird and bat populations.
Adults: Mature moths have forewings which are relatively narrow and smoothly curved at the bottom. These can vary from brown to reddy-brown with a black dot on the edge of each wing. The characteristic hindwings are yellow, with a black band at the bottom. Larvae: Cutworms are usually green, brown, grey, or yellow soft-bodied caterpillars, often with black longitudinal stripes or dashes, and semi-circles, measuring up to 2.5cm in length. Eggs: Spherical and pale yellow when freshly laid, darkening slightly with age. Laid beneath leaves of plants in large clusters in areas of overgrowth.
Defoliate plants. Stems can be 'cut', causing plants to collapse. Complete destruction of seedlings. Cutworm droppings. Leaves can be stripped. Moths are readily attracted to porch lights and lamps.
North America, Europe and some parts of North America (Colorado, Michigan)
These caterpillars have plenty of natural enemies that can keep them at bay. These include spiders, frogs, parasitic wasps and flies, small mammals like rodents, and birds. Cutworms are hosts for numerous parasitoid wasps and flies, including species of Braconidae, Ichneumonidae, Tachinidae and Eulophidae. Cutworms favour overgrown areas where there is lots of coverage, so if you have a treasured plant and vegetable patch, you should keep these tidy. This will make the area unattractive to cutworm moths. By keeping vegetable plots well-watered, you make the environment unfavourable to cutworms. When cultivating food crops, you may expose a pupa or caterpillar. These should be relocated (somewhere the birds can see them!). When infestations seem heavy, you can pick them off your plants by hand, which is best done at night. Diatomaceous earth can be used as a barrier against these pests, sprinkle over foliage and soil surrounding the stems. Fleece and insect-proof mesh placed above vegetable patches have been proven to make infestations less frequent. Likewise, plastic coverings for seedlings are encouraged. Cutworms hide beneath topsoil during the day. You can water bacteria Bacillus thuringiensis into the soil, which will kill the caterpillars. Alternatively (if suitable), beneficial nematodes can be purchased from some commercial retailers. Watering these into the soil should eliminate cutworms in the soil. Soil temperatures need to be between 12-20ºC for the treatment to be effective. Always take care to research products to make sure they are the right solution to your problem! Always read instructions prior to application.