How to Manage Pests

UC Pest Management Guidelines


Saltmarsh Caterpillar

Scientific name: Estigmene acrea

(Reviewed 11/05, updated 1/10)

In this Guideline:


Saltmarsh caterpillar is one of the woollybear caterpillars that has long hairs covering the entire body. Their hairs are generally of sufficient density as to completely hide the skin. They are typically black at each end with a median band in between of brown or reddish brown hairs. They also exhibit yellowish spots on the sides. The hairs are called urticarial hairs and may produce a stinging dermatitis (rash) on the skin of sensitive individuals.


Caterpillars eat leaves. Young caterpillars skeletonize leaves while large, older caterpillars consume all of the leaf except the major veins. Small larvae are usually found feeding in groups on the underside of the leaves.


Biological Control

The eggs are attacked by a number of predators and parasites. While the dense body hairs on the larvae effectively deter some of the potential predators and parasites, larvae are attacked by several diseases.

Monitoring and Treatment Decisions

No economic thresholds have been developed for saltmarsh caterpillars, which tend to be somewhat cyclic in their nature, with damaging populations occurring every 3 to 4 years. While present in other years, numbers are generally low, and severe injury rarely occurs.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
The following materials are listed in the order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees as well as the environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
  (various products) Label rates 4 0
+ 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.
# 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 more information, see



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Sugarbeet
UC ANR Publication 3469

Insects and Mites

E.T. Natwick, UC Cooperative Extension Imperial County
Acknowledgement for contributions to Insects and Mites:
C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
D. R. Haviland, UC IPM Program, Kern County
L. D. Godfrey, Entomology, UC Davis

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