How to Manage Pests

UC Pest Management Guidelines


Saltmarsh Caterpillar

Scientific name: Estigmene acrea

(Reviewed 11/05, updated 1/10, pesticides updated 9/16)

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 per acre REI‡ PHI‡
(Example trade name)   (hours) (days)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
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, 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.
  (Intrepid 2F) 8–16 fl oz 4 7
  (various products) Label rates 4 0
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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).



[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 and UC Cooperative Extension, Kern County
L. D. Godfrey, Entomology, UC Davis

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