Carrots XXVIII – 2

Webworms, Cutworms, Other Defoliators

Whitney S. Cranshaw and Michael J. Brewer

Cutworm Adult	Cutworm Larva

Identification (and life cycle/seasonal history)

The immatures of various species of moths may occasionally become abundant in carrot. The moths are typically about one inch long and fully grown larvae are about 38 millimeters (1¹/₂ inch) long. Larvae may feed on the underground stem and foliage. For several of the species, larvae overwinter half-grown in the soil and ground litter.

Plant Response and Damage

The feeding activity of larvae of various species of moths may occasionally result in unacceptable defoliation and stem cutting.

Cultural Control

Larvae of several of these species may become abundant in early season weeds along field edges and move into the field as the weeds dry down or are defoliated. Therefore, consistent weed control along field edges will reduce the larval population.

Chemical Control

When damage is noticed, a close inspection of the entire field will help determine the extent of the damage. At times, populations of these larvae will be limited to field edges, in which case an insecticide application can be selectively applied.

Product list for Webworms, Cutworms, other defoliators:
Insecticide	Product per acre	Preharvest Interval, remarks
Dipel 2X, Biobit W Dipel 4L, Biobit F Javelin WG	0.5-2.0 lb (0 days) 0.5-2 pt 0.25-1.0 lb	Bacillus thuringiensis product. Most formulations are acceptable under current regulations for Certified Organic produce. Stomach poison activity. Labelled for application through sprinkler systems.
Sevin XLR+^1, 4F^1 Sevin 80S^1 Sevin 5OW^1	1-2 qt 1.25-2.5 lb 2-4 lb	(O days) A carbamate insecticide (carbaryl). The 80S, 4F, and 5OW formulations are highly hazardous to bees. Some rotational restrictions. May be used with sprinkler irrigation. 12 to 24 hour reentry proposed.
Lannate 90S^R Lannate L^R	0.25-0.5 lb 1-2 Pt	(1 day) Restricted Use. Carbamate insecticide (methomyl). 48 hour reentry interval proposed. Not registered for chemigation.
Asana XL^R	5.8-9.6 fl oz	(7 days) Proposed 24 hour reentry interval. Has given superior control of aster yellows in University trials. Pyrethroid insecticide (esfenvalerate). Ground application only. Some rotation restrictions with root crops.
Methyl parathion 4E^RMethyl parathion 7.5^R	1 qt 0.5-1 Pt	(15 days) 7 hour reentry proposed. Labeled for armyworms and cutworms. Do not use treated tops for food or feed.
Baythroid 2^R,1	1.6 fl oz	0 days. Pyrethroid insecticide. Maximum 5 applications per season, with minimum 7 day interval between treatments.
^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.

Categories: Carrot, Webworms, Cutworms, Insects

Date: 05/05/2002