HPIPM:Western Bean Cutworm FC
Author: Frank B. Peairs[1]
Identification (and life cycle/seasonal history)
Western bean cutworm, Striacosta albicosta (Smith), larvae are dark brown with faint diamond-shaped markings on their backs. Fully developed larvae are about 38 millimeters (1.5 inches) in length and have three short dark stripes running lengthwise on the first segment behind the head. The body of the moth is about 20 millimeters (0.8 inch) long and brown in color. They have a wingspread of about 40 millimeters (1.6 inches) and are marked with creamy white stripes on the front leading edge. The light colored hind wings are not distinctly marked.
Western bean cutworms complete a single generation each year. Fully-grown larvae (pre-pupae) overwinter in the soil. In May and early June they change to pupae. The moths emerge between mid-July and early August. They are active at night and are attracted to lights. Eggs are laid shortly after the moths emerge. The eggs are deposited in clusters of four to 200 on the top surface of upper leaves. When first laid the eggs are white with a thin red ring around the top. As they age, they change to brown, then immediately prior to hatching they are purple to black in color. The eggs hatch in five to seven days. The majority of the western bean cutworms feed until mid-September. When mature, they enter the soil and change to the pre-pupal stage to overwinter.
Plant Response and Damage
Western bean cutworm was originally considered to be a pest of dry beans but now is recognized as a serious pest of field corn. Following hatch, young western bean cutworms move to one of two places on the corn plant, depending on the stage of development of the corn. If corn has not tasseled, larvae feed on pollen in the developing tassel. If corn has tasseled, larvae feed on silk in the ear: this type of silk feeding may cause pollination to be poor. Once the ear has formed, larvae feed on developing kernels. Destruction of the kernels may reduce corn yields by as much as 30 to 40 percent.
Management Approaches
Resistant Varieties
Control is expected with only those Bt corn hybrids containing the Vip3A toxin (Agrisure Viptera, Agrisure Duracade 5222). See Managing Corn Pests with Bt Corn, [2], for details on the use of Bt corn hybrids to control corn pests. See [3] for an excellent summary of currently available traits.
Chemical Control
Western bean cutworm eggs are laid on upper leaf surfaces on the upper part of the plant. Fields should be scouted closely, as once the larvae move into the ear, good control will be difficult to obtain. Chemical control should prove economical if eight percent or more of the plants have egg masses or small larvae in the tassels, and the crop is at least 95 percent tasseled. If tasseling is much less than this, the percentage of infested plants should be raised as fewer larvae are likely to reach the ears. Many of the insecticides registered for western bean cutworm control have been associated with spider mite outbreaks, so fields should be monitored for mites after a treatment is made.
Product list for western bean cutworm:
| Pesticide | Product/Acre (Fl oz. or oz. product) | Preharvest Interval, remarks |
|---|---|---|
| FastacR,1 | 2.7 - 3.8 | 30 days grain and stover, 60 days forage. 12 hr REI. Extremely Hazardous to Bees! No more than 11.4 fl oz per season. |
| Bacillus thuringiensis1,2 | See labels | 0 days. 4 hour REI. Use of a spreader-sticker is recommended. |
| Beauveria bassiana1,2 | See labels | 0 days. 4 hr REI. Potentially pathogenic to bees; avoid applying where bees are foraging or around hives. |
| beta-cyfluthrinR,1,2 | See labels. | 21 days. 12 hour REI. See labels. Extremely Hazardous to Bees! |
| 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! |
| carbaryl1,2 | See labels | 48 days grain and stover, 14 days silage. 12 hour REI. Extremely Hazardous to Bees! |
| Prevathon | 14-20 | 14 days grain, 1 day fodder, forage, stover, silage. 4 hour REI. Do not apply more than 0.2 lb ai/acre/crop. |
| 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! |
| Grandevo1 | 1-3 lbs | 0 days. 4 hour REI. May be repellent to bees. |
| cyfluthrinR,1,2 | See labels | 21 days. 12 hour REI. See labels. 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! |
| Belt1 | 2 - 3 | 28 days grain, 1 day forage and silage. 12 hour REI. |
| 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! |
| BesiegeR | 6 - 9 | 1 day for forage, 7 days for hay. 24 hr REI. Make applications when bees are not actively foraging by applying during early morning or evening hours. See labels for additional restrictions for individual active ingredients. Do not apply more than 31 fl oz product/season. |
| methoxyfenozide2 | See labels | 21 days. 4 hour REI. No more than 1.0 lb AI/A/season. See label for timing information and crop rotation restrictions. |
| methomylR,1,2 | See labels | 21 days to harvest grain or fodder. 3 days to forage. 48 hour REI. Do not apply more than 2.25 lb ai/acre/crop. 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! |
| Radiant SC1 | 3 - 6 | 28 days. 3 days forage or fodder. 4 hour REI. Highly toxic to bees! |
| spinosad1,2 | See labels | 28 days grain, 3 days fodder or forage. |
| 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 | 2.7 - 4.0 | 7 days. 12 hour REI. Extremely Hazardous to Bees! No more than 0.10 lb AI/A/season. |
| StallionR,1 | 9.25 - 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.
