Sorghum XV-5

Cutworms

John B. Campbell

Cutworm Adult	Cutworm Larva

The dingy or dark sided cutworms may cause damage to sorghum particularly in areas of the field that may have been weedy the preceding fall. The cutworms overwinter as larvae and tend to feed more on leaves rather than cut stems at the soil surface. They sometimes are referred to as "climbers" since they crawl up the stalk and feed on the leaves.

Identification (and life cycle/seasonal history):

These two species have one generation per year. Eggs are deposited on the stems of grasses and weeds or behind the leaf sheath. Egg hatch occurs in two days to two weeks dependent on the species and temperatures. They may feed some in the fall. As the weather turns colder, they seek shelter under clods or in the debris of the weedy plants. In the spring as temperatures warm, they again become active and feed until the larval growth is completed. They then tunnel down in the soil to pupate. When the adults emerge, they exit via the tunnel made by the larvae.

The dingy cutworm is a pale grayish-brown that may have a reddish-brown tinge. There are faint, dark, V-shaped markings on the back of each abdominal segment. The dark-sided cutworm's subdorsal coloration includes a narrow, dark-brown stripe followed ventrally by a broad pale stripe and below this is a dark brown stripe just above the spiracle.

Management Approaches

Cultural Methods

Weed control in the late summer or fall will be beneficial. The cutworm moths are attracted to grassy or weedy areas for egg deposition.

Chemical control

Sampling/Surveying/Timing of Sampling

Plants with leaf feeding or that have been cut off at ground level should be checked for the presence of cutworms. They should be in the soil around the damaged plants. Generally, only seedling plants will be damaged by cutworms.

Economic thresholds

Generally sorghum, even in dryland or ecofallow systems, is planted at population levels that can tolerate considerable loss without realizing a yield reduction. In addition, a sorghum plant will sucker which replaces the lost or damaged stalk.

Product List for Cutworms

	Insecticide	Product Per Acre (Fl oz. or oz. product)	Preharvest interval, remarks
	Asana^R	0.03 – 0.05 lb (5.8 – 9.6 fl.oz.)	Labeled only east of the Rocky Mountains and west of the Mississippi River. Repeat necessary for control. Do Not exceed 0.15 lbs active ingredient per acre per season. See label for spray recommendations.
	Baythroid 2EC	1.0-1.3 fl.oz. of 2 lb/gal EC	See label for use directions and restrictions.
	Lorsban 4E	(2 pints)	See label for grazing, harvest and variety restrictions. Limit 3 qts/A/yr
	Warrior^R	1 lb/EC(2.56_3.84 fl.oz.)	See label for use directions and restrictions.
^RRestricted Use Pesticide.
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.

Categories: Sorghum, Insects, Cutworms

Date:12/18/06