Cutworm

Noctua pronuba

Cutworm, Large Yellow Underwing, Yellow Cutworm, Snywurm (Afr.)

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Noctua pronuba is known by the name 'Yellow Underwing' after it's striking pair of hindwings. The larvae are sometimes called cutworms because they can be plant pests. They're known to damage the plant by boring into the stems, ultimately causing the plant to be cut at the stem. Cutworms are not worms, biologically speaking, but caterpillars. The common name 'cutworm' refers to many species in the Owlet moth family. In the garden, they can be found on leaves, buds and stems, and unfortunately, can be quite destructive in some cases. As adults, the moths will feed on sugary substances like nectar from flowering plants, and can provide pollination services in the garden.
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Traits

Will attack the stems of plants, eventually cutting the plant down.
These moths can help support bird and bat populations.

Appearance

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.

Symptoms

Defoliate plants and complete destruction of seedlings, stem and entire plant. Stems can be 'cut', causing plants to collapse. Cutworm droppings. Leaves can be stripped. Moths are readily attracted to porch lights and lamps.

Activity

Nocturnal

Personality

Order

Lepidoptera

Family

Noctuidae

Metamorphosis

Complete

Distribution

North America, Europe and some parts of North America (Colorado, Michigan).

Biological treatment

These caterpillars have plenty of natural enemies that can keep them at bay. These include spiders, frogs, parasitic wasps and flies, small mammals and 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. 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.

Chemical treatment

Currently unavailable

Attracts this pest

Cutworms feed on herbaceous plants, vegetable crops and grasses. The moths are attracted to the flowers of ornamental plants.
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Knowledge and advice

Search our ever-growing knowledge base to find plants and information. Find out about pests and diseases you should be keeping an eye out for. Watch How to videos or follow step by step guides for tasks in the garden. Free download for your phone or tablet.
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