How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

The saltmarsh caterpillar is most abundant in August and September, but damaging populations are sporadic. Eggs are spherical, whitish, somewhat flattened, about 3/100 inch (0.75 mm) in diameter, and found in naked clusters on the undersurface of leaves. Young 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. Young larvae feed in groups, but as they grow they disperse and start feeding individually.

DAMAGE

Damage by saltmarsh caterpillar consists primarily of defoliation.

MANAGEMENT

Start inspecting plants for saltmarsh caterpillar damage along with other pests and their damage during the vegetative growth stage; continue to monitor these caterpillars from bud to blossom and during the pod fill period. Specific treatment thresholds have not been established for these foliage feeders. Late-season infestations are insignificant. If damaging numbers are encountered mid-season when excessive foliage loss may reduce crop production, a treatment may be warranted.

Common name		Amount/Acre**	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)
When choosing a pesticide, consider information relating to the impact on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
A.	BACILLUS THURINGIENSIS ssp. KURSTAKI#
	(various products)	Label rates	4	0
	MODE OF ACTION GROUP NUMBER1: 11.B2
	COMMENTS: Does not destroy natural enemies of corn earworm. Control is maximized by thorough coverage and by making applications when larvae are small.
B.	ACEPHATE
	(Orthene) 75 SP	0.67 lb	24	14
	MODE OF ACTION GROUP NUMBER1: 1B
	COMMENTS: Use of product may result in mite outbreak. Highly toxic to honey bees; do not apply when bees are present.
C.	METHOMYL*
	(Lannate SP)	0.5–1 lb	48	14
	MODE OF ACTION GROUP NUMBER1: 1A
	COMMENTS: Highly toxic to honey bees; do not apply when bees are present. Do not apply more than 4.5 lb a.i./acre/crop.
**	Mix with sufficient water to obtain full 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 grown produce.
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/.

PUBLICATION

UC IPM Pest Management Guidelines: Dry Beans
UC ANR Publication 3446
Insects and Mites
L. D. Godfrey, Entomology, UC Davis
R. F. Long, UC Cooperative Extension, Yolo County

Top of page