Winter cutworm is the common name for the larval stage of the large yellow underwing moth (Noctua pronuba [Lepidoptera: Noctuidae]). The cutworm has tolerance for cold temperatures, and larval feeding activity persists throughout fall and winter.
Adult N. pronuba moths have been detected in Oregon for at least a decade, and the species is common in many different ecological habitats. Epidemic outbreaks of adult moths have occurred periodically in this region, resulting in captures of up to 500 moths per night. However, larval feeding by N. pronuba has not been a problem in Oregon until recently. In 2013 and 2014, there were isolated instances reported, including damage by larvae to sod near Portland and defoliation of herb and flower gardens in Corvallis. In 2015, large numbers of larvae were observed around homes, within golf courses, and in field crops located in Oregon and Washington.
Winter cutworms have a wide host range across agricultural, urban and natural landscapes (Table 1) and are a concern as a potential crop pest that can cause considerable damage in a short amount of time. Above-ground damage occurs when larvae chew through tissues near ground level, cutting the stems off plants. Leaf chewing and root feeding also have been observed. Winter cutworms are gregarious, which means they feed and move in groups, similar to armyworms. The severity of plant damage they cause can differ depending on specific environmental conditions, proximity to other host plants and management practices. This publication highlights general information about winter cutworm, including identification, scouting recommendations and potential control measures.
Distribution
The large yellow underwing moth (Noctua pronuba L.) is native to Eurasia and is widely distributed throughout the Palearctic region and North Africa. The first documented account of N. pronuba in North America was made in July 1979 in Halifax, Nova Scotia, where a single male moth was found at a porch light. The moths are particularly strong fliers and can migrate over large distances. Moths can deposit eggs on a variety of ornamental plants imported by the horticultural industry, so it is possible that this species arrived to North America via trade routes. After being introduced, N. pronuba spread rapidly to the northeastern United States. By 2000, moths were detected in Illinois, Wisconsin, Colorado and Wyoming. Although the adult moth is now considered widespread in the U.S., there are very few published reports of larval damage occurring on crops.
The first report of winter cutworm activity in the U.S. was made in 2007, when large numbers of larvae were noted around homes and in hayfields throughout Michigan. Another instance of large-scale larval feeding was reported in winter wheat in Idaho. Potential damage to crops by winter cutworm in Oregon has not been previously described but is a concern due to the recent and significant increase in the number of larval sightings.
Identification and biology
A noctuid moth life cycle is composed of four developmental stages: adult, egg, larva and pupa. According to published literature, N. pronuba has one generation per year in Eurasia and other areas of origin, with adult flight occurring from June through October. However, trapping efforts conducted in the Pacific Northwest reveal an activity pattern that suggests bivoltinism (two generations per year). There seems to be a slight but distinct increase of flight activity occurring in April through June, and another, larger peak beginning in mid-August and continuing through October.
|
Group |
Host plant |
|---|---|
| Small fruits |
• Grape • Strawberry |
| Grass or forages |
• Alfalfa> • Clover • Oat • Orchardgrass • Poa spp. (Annual bluegrass, Kentucky bluegrass, others) • Ryegrass • Wheat |
| Ornamentals |
• Carnation • Clary sage • Heartsease • Hosta • Ivy • Chrysanthemum • Mint • Iris • Primrose • Violet • Wallflower |
| Others |
• Canola • Desert saltbush |
| Vegetables |
• Beet • Carrot • Cole crops • Lettuce • Potato • Swiss chard • Tomato |
| Weeds |
• Burdock • Chickweed • Dandelion • Dock |
Adult moths are polymorphic, meaning many variations of color and patterning exist. (Figure 1). The dull, gray-brown coloring of the forewing (top wing) makes them difficult to identify while at rest. In flight, adults are easily recognizable by their large, 2-inch (50–60 millimeter) wingspan and colorful hindwing (bottom wing), which is bright yellow to orange with a thick, dark marginal band (Figure 1).
Eggs are laid in flat sheet clusters that may be difficult to find in the field. The eggs are spherical in shape, ribbed and reticulate and cream-colored to yellow, but darken over time. Egg masses are laid on the underside of host plants as well as on nonplant structures. One female moth can deposit up to 2,000 eggs in her lifetime. Eggs hatch after two to four weeks, depending on temperature.
Larvae are smooth-bodied and progress in color from green to dark brown, olive or gray as they mature. They are about ⅛–2 inches long (3–50 millimeters). Mature larvae are characteristically marked with a series of black dashes that run down the sides of the back (Figure 2a). Dashes are most prominent towards the posterior end. There is a light-colored line underneath the dashes, and white to cream-colored slanted lines on the sides of the body may be evident. The head is tan, with a pattern of two black, angled crescents that point inward (Figure 2b).
Winter cutworms are present in the soil from September through March and exist at varying life stages and maturity. It is presumed that the more mature larvae pupate during the winter and emerge as adults in early spring. Other, younger larvae continue to feed through the winter and spring. After larvae mature, they develop into reddish-brown pupae about 1 inch long (25 millimeters) and rest in earthen cells under soil or debris (Figure 3). The developmental stages present in our sampling efforts to date vary by site, but include mid- to late-stage larvae and a small percentage of pupae. Further study is necessary to clarify the life cycle of Noctua pronuba in the Pacific Northwest.
|
Common name |
Latin name |
Notes on activity of larvae (L) and adults (A) |
Larval key characteristics |
|---|---|---|---|
| Winter cutworm | Noctua pronuba |
L: move in masses; can actively feed all winter if temps are mild A: migratory; long-season (April–Nov.); may have two overlapping generations |
Black dashes bordered by a cream-yellow line that are most noticeable near posterior end; tan head with two black arcs on the eyes (see other notes in ID section) |
| True armyworm | Mythimna unipuncta |
L: move in masses; most common in grasses and grains A: migratory; long-season (May–Nov.); move to higher elevations in late summer, then return for peak egg-laying activity in Sept.–Oct. |
One broad, dark dorsal band; three lateral stripes that contrast in color, the lowest of which has a pink hue; small head with net-like markings and dark arcs on the eyes |
| Variegated cutworm | Peridroma saucia |
L: overwinter as semi-mature larvae, can be found in the soil and under field debris A: migratory; long activity period; suspected to have two generations (May–June and late Aug.–Oct.) |
A series of four to seven small, yellow dorsal spots; terminal body segment has a transverse yellow line and a black "W", which is most evident on mature larvae |
| Spotted cutworm | Xestia c-nigrum; Xestia xanthographa |
L: prone to climb; overwinter as larvae A: two distinct flight-activity periods (April–June and late July–Nov.) |
May have black dashes or bold, triangular shaped markings, most prominent on the posterior body segments; side of body has a wavy black line; head is light brown with dark markings on the eyes |
Distinguishing from other common cutworms and armyworms
There are other larvae that look similar to winter cutworm, all of which are found within the Noctuid moth family. Distinguishing between them is crucial for the most effective pest management approach, as they can behave differently and feed during different times of the year. Related agricultural pest species that could be confused with winter cutworm in this region include variegated cutworm (Peridroma saucia), spotted cutworm (Xestia spp.), Western yellowstriped armyworm (Spodoptera praefica), army cutworm (Euxoa auxiliaris), black cutworm (Agrotis ipsilon), glassy cutworm (Apamea devastator) and true armyworm (Mythimna unipuncta). Differences between some of these species are highlighted in Table 2.
Scouting and damage
Visual monitoring is the easiest way to detect an armyworm or cutworm attack. Typically, cutworm damage is erratic and less uniform than armyworm damage. However, winter cutworms move en masse like armyworms, so look for large areas of clipped, mowed or notched foliage (Figure 6 and Figure 7), or, in some cases, missing plants within and across rows. Spend time visually searching for damaged foliage and the presence of larvae in at least five locations.
Winter cutworm larvae are mostly nocturnal and hide during the day, but daytime feeding can occur on mild or overcast days. It may be necessary to scrape and sort through at least the top 2 inches (5 centimeters) of soil to sight larvae during the day. Cutworms often curl up into a “C-shape” when disturbed (Figure 4). Use a soil scoop and check near the base of plants or crowns and under clods, leaf litter or thatch. Adult moths are nocturnal and can be sampled with a light trap.
At this point, factors that influence feeding by winter cutworm are unclear. Based on what we know from other reports, feeding may be intensified in perennial crops (especially fall-seeded crops), or areas with reduced tillage, volunteer cereals or persistent, low-growing winter weeds. Areas with low, wet margins also may have an increased risk of cutworm feeding. However, field edges or centers can be equally affected, depending where eggs were laid. Other factors that could influence a sudden outbreak include climate, mass migration of adults into the region and proximity to neighboring weedy areas.
Management tactics
Correct pest identification is important when selecting the appropriate management method. Pest behavior, seasonality and susceptibility to control tactics can vary widely between species. See “Identification and biology” or contact a county Extension educator if you are not sure the damage is being caused by winter cutworm.
Following an integrated pest management (IPM) plan that combines cultural, biological and chemical strategies is likely the best approach. Options will vary depending on the scenario. Also, because this is the first recorded occurrence of crop damage by winter cutworm in this region, it is not certain how effective control tactics will be.
Cultural practices
Following standard cultural control methods to reduce insect pest pressure in general also may reduce the potential for damage by winter cutworm. In cropping systems, recommended strategies include rotating crops, removing weeds and plant residue along field edges to reduce egg-laying and feeding sites and tilling before planting to expose overwintering larvae and pupae and potentially reduce populations. In lawns, mowing regularly, irrigating in the summer and applying enough fertilizer to maintain good density is recommended.
Biological agents
Armyworm and cutworm larvae populations are typically kept below a damaging level by natural control agents such as parasitic wasps, flies and nematodes, bacterial and viral diseases and general predators (ground beetles, birds and rodents). Predation and parasitism of winter cutworm in Oregon has been documented in field collections from a volunteer rye field (Figure 9). Yet, at this point, the widespread impact of biological control on winter cutworm by beneficial organisms in the Pacific Northwest is unclear.
Insecticides
Currently registered insecticides that effectively control cutworms and armyworms in different crops can be found by searching the Pacific Northwest Insect Management Handbook. This resource is updated annually and should be considered the primary source for the most up-to-date insecticide recommendations. For convenience, we have distilled information about commonly used products for cutworm and armyworm control in crops that may be affected by winter cutworm (Table 3). Please note that there is limited information available about the efficacy of products against winter cutworm specifically.
The following points are important to remember when implementing a chemical control strategy:
- In general, small, younger larvae (shorter than 1 inch) are more susceptible to insecticides than larger, mature ones.
- Fall rains may help incorporate insecticides into the soil where larvae are feeding, but too much rain may carry insecticides below the target pest.
- Consider using “reduced risk” insecticides rather than broad-spectrum products in order to lessen the effects on natural enemies and pollinators.
- Rotating among products with different modes-of-action (MOA) may yield better results and reduces risk of development resistance.
- If possible, apply insecticides late in the day to maximize exposure to night-feeding larvae.
- Pesticides may require repeat application, specific modes of incorporation, and other specifics that can be learned only by read-ing the product label. ALWAYS READ THE LABEL.
|
Active ingredient |
Product name (example) |
MoA group3 |
Notes4 |
|---|---|---|---|
|
Grass seed (annual and perennial — see notes) |
|||
| lambda-cyhalothrin | Warrior | 3A | Restricted-use pesticide. |
| zeta-cypermethrin | Mustang | 3A | Restricted-use pesticide. Do not make applications less than seven days apart. |
| cyfluthrin | Baythroid XL | 3A | Only effective against small larvae. |
| bifenthrin | Brigade | 3 | Restricted-use pesticide. Consult label for PHIs and grazing restrictions. |
| carbaryl | Sevin | 1A | --- |
| chlorpyrifos | Lorsban | 1B | For use on perennial grass seed only. 24c Special local needs (SLN) labels OR-090009 (no more than three applications per year); WA-090010 and ID-090003 (can be used only in first year of establishment). |
| spinosad | Blackhawk, Success | 5 | --- |
|
Leguminous, forage and seed crops (alfalfa, clover, vetch) |
|||
| chlorantraniliprole | Coragen | 28 | Alfalfa grown for seed only. Do not make more then one application per cutting. Relatively safe to beneficial insects, but consult label regarding bloom periods. Toxic to fish and aquatic invertebrates, use caution to avoid drift or runoff to neighboring waterways. |
| lambda-cyhalothrin | Warrior | 3A | Restricted-use pesticide. Do not apply while bees are active. Advisable to move bee shelters for two to three days after application. |
| zeta-cypermethrin | Mustang | 3A | Restricted-use pesticide. For use on alfalfa grown for seed and vetch grown for seed only. Do not make applications less than seven days apart. Consult label for grazing PHIs. |
| permethrin | Cutworm Bait | 3A | Restricted-use pesticide. For use on alfalfa grown for seed only. Do not apply more than 40 pounds of product per acre per cutting. Avoid application when bees are foraging. Do not apply to mixed stands. |
| carbaryl | Sevin | 1A | For forages only (not seed crops). May cause temporary bleaching of young alfalfa. Most effective against cutworms that feed on upper portions of the plant. |
| azadirachtin | Azera | UN | For forages only (not seed crops). Use higher rates on mature larvae. |
| bifenthrin | Brigade | 3 | Restricted-use pesticide. 24c Special local needs (SLN) labels OR-070013 and WA-070015. Alfalfa seed and clover seed only. Do not graze after application. Do not feed treated hay. Processed seed must be labeled. |
| bifenthrin | Discipline | 3 | Restricted-use pesticide. 24c Special local needs (SLN) labels OR-040039 and WA-040027. Alfalfa seed and clover seed only. Do not graze after application nor feed treated hay. Seed must be labeled before sale and distribution. |
| chlorpyrifos | Lorsban | 1B | Forage alfalfa is listed, but 24c special local needs (SLN) label OR-090010 is for clover seed only. Do not graze after application. Do not feed treated hay. Seed must be labeled before sale and distribution. Highly toxic to bees; do not apply if bees are foraging. |
| Bacillus thuringiensis (Bt) ssp. kurstaki or aizawai | various products | 11A | Most effective on small larvae. Thorough coverage of foliage is important. Ineffective if larvae do not eat plant tissue treated with Bt. Repeat applications may be necessary. A spreader-sticker (adjuvant) may improve performance. |
| spinosad | Success, Entrust | Supplemental label specifies "Legume forages and legume forage grown for seed." Some formulations are approved for organic use (e.g. Entrust). | |
|
Brassica and radish crops (crucifer vegetables, radish, canola) |
|||
| carbaryl | Sevin | 1A | For brassica leafy vegetables; Sevin 5 Bait may be used on radish and turnip. Canola not listed. |
| methomyl | Lannate LV or SP | 1A | Restricted-use pesticide. Add a wetting agent to improve coverage. Pre-harvest intervals (PHIs) range from one to three days, consult label. |
| esfenvalerate | Asana XL | 3 | Restricted-use pesticide. For broccoli, Brussels sprouts, cabbage, cauliflower. Pre-harvest intervals (PHIs) range from three to seven days, consult label. |
| bifenthrin | Sniper, Brigade 2EC, Capture LFR | 3 | Restricted-use pesticide. Do not make applications less than 14 days apart. |
| azadirachtin | Azaguard | UN | Botanical insecticide. Most effective against small larvae. Repeat application every five to seven days (nonfood crop) or seven to 10 days (food crop). |
| indoxacarb | Avaunt | 22 | Do not apply more than 14 ounces of product per acre per season. Add a wetting agent to improve coverage. |
| permethrin | Cutworm Bait | 3A | Restricted-use pesticide. Approved for use on many brassica vegetable crops, but not on radish or canola. May be used on turnips in WA only. Toxic to bees, fish, and aquatic invertebrates. Avoid application when bees are foraging. |
| tebufenounceside | Confirm | 18 | Not labeled for radish. Equally effective on all stages of larvae, assuming thorough coverage and higher rates. Re-application every 10–14 days will be necessary. Potential groundwater contaminant. |
| chlorantraniliprole | Coragen | 28 | Broad-spectrum diamide. Relatively safe to beneficial insects, but consult label regarding bloom periods. Toxic to fish and aquatic invertebrates, use caution to avoid drift or runoff to neighboring waterways. |
| Bacillus thuringiensis (Bt) ssp. kurstaki or aizawai | Dipel, Javelin, Attack, Thruicide, Certan | 11A | Only effective on small larvae (less than 0.5 inch long). Thorough coverage of foliage is important. Sunlight inactivates Bt on foliage, so make applications in the evening if possible. Repeat applications may be necessary. |
| lambda-cyhalothrin | Warrior | 3A | Restricted-use pesticide. Do not apply while bees are active. |
| zeta-cypermethrin | Mustang | 3A | Restricted-use pesticide. Do not make applications less than seven days apart. PHIs vary by crop, consult label. |
|
Small grains (wheat, barley, oat, rye, triticale) |
|||
| methomyl | Lannate SP | 1A | Restricted-use pesticide. May be used on barley, rye, oats, and wheat. Do not graze within 10 days. Do not apply more than 1.8 pounds ai per acre per crop. Highly toxic to bees. |
| chlorpyrifos | Lorsban | 1B | Restricted-use pesticide. Wheat only. Expect suppression only if high infestations or mature larvae. Consult label for grazing and straw PHIs. Do not make more than two applications per season. |
| Bacillus thuringiensis (Bt) ssp. kurstaki/aizawai | Dipel, Javelin, Attack, Thruicide, Certan | 11A | Only effective on small larvae (less than 0.5 inch long). Thorough coverage of foliage is important. Repeat applications may be necessary. |
| cyfluthrin | Baythroid XL, Tombstone | 3A | Tombstone is for wheat only; Baythroid XL can be used on all cereal grains. |
| alpha-cypermethrin | Fastac | 3A | Wheat and triticale only. |
| zeta-cypermethrin | Mustang | 3A | Restricted-use pesticide. four-day PHI for grain, straw, and hay. Do not make applications less than 14 days apart. |
| lambda-cyhalothrin | Warrior | 3A | Restricted-use pesticide. Livestock grazing PHI is seven days. Treated straw PHI is 30 days. |
| azadirachtin | Aza-Direct | UN | Botanical insecticide. Most effective against small larvae. |
|
Vineyards (barrier and foliar — see notes) |
|||
| bifenthrin | Talstar, Onyx | 3 | Restricted-use pesticide. Barrier use only (wires, trunks, posts); minimize contact to foliage. |
| fenpropathrin | Danitol | 3 | Restricted-use pesticide. Apply as a barrier spray before cutworms start moving from the soil to feed on buds and shoots during the dormant period. |
| chlorpyrifos | Lorsban | 1B | Washington and Idaho only. 24c Special local needs (SLN) labels WA-090002 and ID-090004. Apply product as a banded application to the base of vines for cutworm control. Do not apply after bloom. PHI is 35 days. |
| fenpropathrin | Danitol | 3 | Restricted-use pesticide. Supplemental label specifies it may be used as as a foliar spray in WA only (21-day PHI). Consult label for more details. |
| carbaryl | Sevin | 1A | Most effective against climbing cutworms. Do not concentrate on the bunch or visible residues may result. If weeds or cover crop between rows are blooming, mow before application to limit effect on bees. |
| spinetoram | Delegate | 5 | Suppression of mature larvae may require repeat applications. Do not make more than two consecutive applications of spinosad or spinoteram. |
| spinosad | Success, Entrust | 5 | Suppression of mature larvae may require repeat applications. Do not make more than two consecutive applications of spinosad or spinoteram. Some formulations are approved for organic use (e.g. Entrust). |
|
Turfgrass (commercial) |
|||
| bifenthrin | Talstar, Onyx | 3 | Restricted-use pesticide. Not for use on sod farms or in commercial seed production. Very toxic to fish and aquatic invertebrates. Do not allow drift or runoff into neighboring waterways. |
| bifenthrin | Capture LFR | 3 | Restricted-use pesticide. May be used on sod; delay irrigation or mowing for 24 hours after application. |
| spinosad | Conserve SC | 5 | Delay watering or mowing of treated area for 12–48 hours after treatment. Do not reapply within less than seven days. |
| Bacillus thuringiensis (Bt) | Deliver, others | 11A | Apply to early instar larvae. Repeat application may be necessary. Breaks down rapidly in sunlight and washes readily off leaves. Do not irrigate for 2 days after treatment. |
| carbaryl | Sevin | 1A | --- |
| azadirachtin | Azatrol, Neemix, Azaguard | UN | Most effective on young larvae. Can be used on both warm- and cool-season grasses. Irrigate well before applying. A crop oil concentrate will help the spray to penetrate turf. |
| beta-cyfluthrin | Tempo | 3A | --- |
| carbaryl | Sevin | 1A | Will persist in the application area for up to several weeks. Should not be applied to blooming plants or to lawns containing clovers or other flowering plants since it is highly toxic to bees and other pollinators. |
| chlorantraniliprole | Acelepryn | 28 | Broad-spectrum insecticide in the diamide class. Notably safe on terrestrial, beneficial predatory insects but hazardous to aquatic invertebrates, including oysters and shrimp. Not for use on turf grown for seed production. |
| cyantraniliprole | Ference | 28 | Broad-spectrum insecticide in the diamide class. Spray drift and residues are toxic to bees; avoid use if bees are foraging. Hazardous to aquatic invertebrates and classified as a high-risk water contaminant. Consult label for groundwater advisories. Not for use on turf grown for seed production. |
| indoxacarb | Provaunt | 22A | Can be used near waterways and around vegetative ornamentals. |
|
Home lawn |
|||
| azadirachtin | BioNeem | UN | A botanical pesticide extracted from the seeds of the neem tree. Used to control cutworms, armyworms, and the larvae of lawn moths. Noticeable efficacy may take many days. Best results with repeat applications. Approved for organic use. |
| spinosad | Green Light with spinosad | 5 | Naturally based insecticide derived from soil microorganisms. Approved for organic use, but does have broad-spectrum activity, and therefore may harm bees and other beneficial insects. |
| carbaryl | Sevin | 1A | Will persist in the application area for up to several weeks. Should not be applied to blooming plants or to lawns containing flowering clovers or other flowering plants since it is highly toxic to bees and other pollinators. |
| chlorantraniliprole | GrubEx1 | 28 | Broad-spectrum control product from the diamide class of insecticides. Meant to be applied once per season; consult label. A potential water contaminant; use caution near waterways. |
| Bacillus thuringiensis (Bt) | Safer's caterpillar killer, many others | 11A | Specific to larvae, but only works on young or small larvae. Thorough coverage of foliage is important. Sunlight inactivates Bt on foliage, so make applications in the evening if possible. Repeat applications may be necessary. Approved for organic use. |
a This list does not intend to promote or discriminate between products, and does not list all available formulations for each active ingredient.
b As of March 2015. For updated information consult the Pacific Northwest Insect Management Handbook and the Pesticide Information Center Online (PICOL).
c Mode of action (MOA) — IRAC classification as of May 2015
d Restricted-use pesticides are available only to currently licensed pesticide applicators. See Oregon Department of Agriculture Pesticide Licensing for more information.
For more information
Bechinski, E., L. Smith, and F. Merickel. 2009. Large yellow underwing; a new cutworm in Idaho. CIS 1172, Moscow, ID: University of Idaho Extension.
Difonzo, C. and H. Russell. 2010. Noctua pronuba (Lepidoptera: Noctuidae): an outbreak in emails. Journal of Integrated Pest Management 1(1): B1-B6.
Powell, J. A. 2002. Noctua pronuba reaches the Pacific Coast. News of the Lepidopterist’s Society. Vol. 44 (4): 120.
Hollingsworth, C. S., ed. 2015. Pacific Northwest Insect Management Handbook.
Crabo, L., Zack, R., and M. Peterson. 2015. Pacific Northwest Moths.
Use pesticides safely!
- Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
- Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
- Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.
Trade-name products and services are mentioned as illustrations only. This does not mean that the Oregon State University Extension Service either endorses these products and services or intends to discriminate against products and services not mentioned.
Acknowledgments
The authors would like to gratefully acknowledge the Oregon State Arthropod Collection staff (C. Marshall, P. Hammond, and D. Ross) for assistance with identification, photography, and ecological accounts of N. pronuba and related species. Input from OSU Extension faculty C. Sullivan, N. Anderson, and S. Filley was instrumental in preparing this publication. S. Angima, B. Braunworth, J. Noller, and L. Brewer provided editorial and administrative support.
About the authors
