HPIPM:Pale Western Cutworm FC
Author: Frank B. Peairs[1]
Identification (and life cycle/seasonal history)
The pale western cutworm, Agrotis orthogonia Morrison, is a subterranean soft bodied caterpillar; grayish-white in color, unmarked by spots or stripes, with two distinct vertical brown bars on the front of the head capsule. A fully developed larva is about 25 millimeters (one inch) in length.
Adult moths emerge from the soil in late summer and fall. Eggs are deposited in loose soil and usually hatch within two weeks. Hatch may be delayed for up to several months if moisture and temperature conditions are unfavorable. Larvae prefer loose, sandy or dusty soil and are found most easily in the driest parts of the field, such as hilltops.
Outbreaks are associated with dry conditions in the previous spring. If the preceding May and June had fewer than 10 days with ¼ inch or more of rainfall, then pale western cutworm populations can be expected to increase. If the preceding May and June had more than 15 such days the cutworm will almost totally disappear. Rainfall events of more than ¼ inch tend to drive the cutworms to the soil surface and expose them to more than usual levels of predation and parasitization.
Plant Response and Damage
Pale western cutworm is a subterranean cutworm feeding on stems at the crown. In corn, the cutworms may cut off small seedlings below ground. As corn plants get larger, they may enter the plant and cause the growing point to die. After feeding is completed, pale western cutworm larvae move to pupal chambers constructed several inches below the soil surface. Adult emergence can begin in late July. Small grains, corn, and a variety of other crops have been damaged by pale western cutworm. They are usually found in corn after a wheat field has been replanted to corn in early spring.
Management Approaches
Because of the sporadic nature of pale western cutworm outbreaks, management options are limited to the use of insecticides. Pale western cutworms seem to feed more under dry conditions, so yield relationships are difficult to define. Consider insecticide treatment if one plant in 20 is injured, and cutworms are present.
Chemical Control
Cutworms are the most prevalent in corn following sod, alfalfa or small grain stubble, and after corn in fields with much crop or weed residue. Early detection of their presence is essential. Crusting or dry surface soil can reduce control with some materials, which can be counteracted by rotary hoeing immediately before or after the application. Pyrethroids have performed better without incorporation in most studies. The effectiveness of current Bt corn hybrids against pale western cutworm is unknown.
Product list for pale western cutworm:
| Pesticide | Product/Acre (Fl oz. or oz. product) | Preharvest Interval, remarks |
|---|---|---|
| FastacR,1 | 1.3 - 2.8 | 30 days grain and stover, 60 days forage. 12 hr REI. Extremely Hazardous to Bees! No more than 11.4 fl oz per season. |
| bifenthrinR,1,2 | See labels | 30 days. 12 hour REI. Use rates below 0.08 lb a.i./acre only if spider mites are NOT a concern. Extremely Hazardous to Bees! |
| HeroR,1 | 4.0 - 10.3 | 30 days to harvest grain or fodder. 60 days to forage. 12 hour REI. See labels for additional restrictions for individual active ingredients. Do not apply more than 0.4 lb ai/acre/crop. Extremely Hazardous to Bees! |
| bifenthrin + chlorpyrifosR,1,2 | See labels | 30 days. 24 hour REI. Maximum 50.5 fl oz product/season. See labels for additional restrictions for individual active ingredients. Extremely Hazardous to Bees! |
| chlorpyrifos 4ER,1,2 | 16 - 32 | 21 days. 24 hour REI. Not for use on popcorn. Extremely Hazardous to Bees! |
| chlorpyrifos + gamma cyhalothrinR,1,2 | See labels | 21 days. 14 days to graze. 24 hour REI. Extremely Hazardous to Bees! See labels for additional restrictions for individual active ingredients. |
| Cobalt AdvancedR,1 | 11-26 | 21 days. 14 days to graze. 24 hour REI. See labels for additional restrictions for individual active ingredients. Extremely Hazardous to Bees! |
| deltamethrinR,1,2 | See labels | 21 days to harvest grain or fodder. 12 days to forage. 12 hour REI. Do not apply more than 0.095 lb ai/acre/crop. Extremely Hazardous to Bees! |
| esfenvalerateR,1,2 | See labels | 21 days. Apply as necessary to maintain control. Extremely Hazardous to Bees! |
| gamma cyhalothrinR,1,2 | See labels | 21 days. 24 hour REI. Do not apply more than 0.12 lb a.i./acre/season. Extremely Hazardous to Bees! |
| lambda cyhalothrinR,1,2 | See labels | 21 days. 24 hour REI. Do not apply more than 0.12 lb a.i./acre/season. Extremely Hazardous to Bees! |
| permethrinR,1,2 | See labels | 30 days grain or fodder. 0 days forage. 12 hour REI. Liquids are Extremely Hazardous to Bees! |
| ConseroR,1 | 2-3 | PHI 28 days, 1 day graze or fodder; REI 24 hrs. See labels for additional restrictions for individual active ingredients. |
| Mustang MaxxR,1 | 1.3 - 2.8 | 7 days. 12 hour REI. Extremely Hazardous to Bees! No more than 0.10 lb AI/A/season. |
| StallionR,1 | 3.75 - 11.75 | 30 days grain or stover, 60 days forage. 24 hr REI. Extremely Hazardous to Bees! See labels for additional restrictions for individual active ingredients. No more than 11.75 oz per application, 35.25 oz per season. |
| SteedR,1 | 3.5-4.7 | PHI 30 days grain, 60 days forage; REI 12 hrs. See labels for additional restrictions for individual active ingredients. No more than 18.7 fl oz product/season. |
| Triple CrownR,1 | 4.5 - 10.3 | PHI 30 days grain, 60 days forage; REI 12 hrs. See labels for additional restrictions for individual active ingredients. No more than 30.7 fl oz product/season. |
| RRestricted use pesticide. 1Labeled for chemigation. 2Generic active ingredient, several formulations. | ||
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.
