How to Manage Pests

UC Pest Management Guidelines

Cotton

Saltmarsh Caterpillar

Scientific Name: Estigmene acrea

(Reviewed 5/13, updated 5/13)

In this Guideline:

Description of the Pest

Saltmarsh caterpillar larvae are hairy and gray when first hatched, then darken to yellow, brownish, or almost black with yellow lines. They are covered with reddish or black hairs, and can be up to 2 inches long when fully grown. Eggs are spherical, whitish, somewhat flattened, about 0.03 inch (0.75 mm) in diameter, and found in naked clusters on the undersurface of leaves.

Damage

Saltmarsh caterpillars are occasional pests that cause the same foliar injury as loopers. Early instars skeletonize leaves, and older instars rag leaves. Extensive defoliation can reduce yield if it occurs before bolls mature.

Management

Heavy infestations seldom occur until late in the season after bolls have already matured. Defoliation in late season usually does not cause economic loss, and may actually benefit the crop by opening the canopy and reducing the chance of boll rot.

Cultural Control

The use of Bt cotton will help prevent damage by saltmarsh caterpillar.

Organically Acceptable Methods

Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on organically grown cotton.

Monitoring and Treatment Decisions

Consider treatment only if extensive defoliation threatens to occur before bolls mature.

Common name		Amount per acre**	R.E.I.‡	P.H.I.‡
(example trade name)			(hours)	(days)
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, also consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
A.	BACILLUS THURINGIENSIS# ssp. KURSTAKI
	(various products)	Label rates	4	0
	SELECTIVITY: High
	PERSISTENCE: Pest: Short NE:2 Short
	MODE OF ACTION GROUP NUMBER1: 11
	COMMENTS: Does not disrupt natural enemies.
B.	SPINOSAD
	(Entrust)#	1.25–2 oz	4	28
	(Success)	4–6 fl oz	4	28
	SELECTIVITY: High
	PERSISTENCE: Pest: Moderate NE:2 Short
	MODE OF ACTION GROUP NUMBER1: 5
	COMMENTS: Use of Success allowed under a supplemental 24(c) registration.
C.	METHOXYFENOZIDE
	(Intrepid) 2F	4–10 fl oz	4	14
	SELECTIVITY: High
	PERSISTENCE: Pest: Moderate NE:2 Moderate
	MODE OF ACTION GROUP NUMBER1: 18
	COMMENTS: An insect growth regulator.
D.	CHLORANTRANILIPROLE
	(Coragen)	3.5–7.0 fl oz	4	21
	SELECTIVITY: High
	PERSISTENCE: Pest: Unknown NE:2 Short
	MODE OF ACTION GROUP NUMBER1: 28
	COMMENTS: Do not apply more than 9 oz/acre/year or make more than 4 applications a year. Do not apply with less than 100 or more than 200 gallons water/acre.
E.	FLUBENDIAMIDE
	(Belt) SC	2 oz	12	28
	SELECTIVITY: High
	PERSISTENCE: unknown
	MODE OF ACTION GROUP NUMBER1: 28
	COMMENTS: A newer material; impact on beneficials not yet determined. Highly toxic to honey bees.
F.	METHOMYL*
	(Lannate) SP	0.5 lb	72	15
	SELECTIVITY: Low
	PERSISTENCE: Pest: Short NE:2 Short
	MODE OF ACTION GROUP NUMBER1: 1A
	COMMENTS: Kills eggs and larvae. Use may redden cotton. According to the label, do not make more than 8 applications per season. Do not graze or feed cotton trash to livestock.
**	Mix with sufficient water to provide complete coverage.
‡	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
*	Permit required from county agricultural commissioner for purchase or use.
#	Acceptable for use on organically produced cotton.
1	Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
2	NE = natural enemies

PUBLICATION

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444

Insects and Mites

• L. D. Godfrey, Entomology, UC Davis
• P. B. Goodell, UC IPM Program and Kearney Agricultural Research and Extension Center, Parlier
• E. T. Natwick, UC Cooperative Extension - Desert Research and Extension Center, Imperial County
• D.R. Haviland, UC Cooperative Extension, Kern County and UC IPM Program

Acknowledgment for contributions to Insects and Mites:

• E. E. Grafton-Cardwell, Kearney Agricultural Research and Extension Center, Parlier
• N. C. Toscano, Entomology, UC Riverside

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