How to Manage Pests

UC Pest Management Guidelines


Saltmarsh Caterpillar

Scientific Name: Estigmene acrea

(Reviewed 1/09, updated 1/09)

In this Guideline:


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 in diameter, and found in clusters on the undersurface of leaves.


In the southern San Joaquin Valley, saltmarsh caterpillars are occasional pests that feed on foliage. They are primarily a problem in fall when neighboring cotton fields are defoliated.


Cultural Control

Ditch or trench around the edges of fields that border cotton.

Organically Acceptable Methods

Cultural control and sprays of the Entrust formulation of spinosad are acceptable for use on organically grown produce.

Monitoring and Treatment Decisions

In fall, if saltmarsh caterpillars are migrating into carrots, a treatment may be necessary.

Common name Amount per acre** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

Calculate impact of pesticide on air quality
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.
  (Entrust)# 1–2 fl oz 4 3
  COMMENTS: Do not apply more than 7 oz of Entrust/acre per crop or more than 4 applications per calendar year. Additional applications must be at least 5 days apart. Use allowed under a supplemental label.
  (Sevin 80S) 1.25–2.5 lb 12 7
  COMMENTS: Ground or air application.
** See label for dilution rates.
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.
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 Groupgroup numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at
# Acceptable for use on organically grown produce.
* Permit required from county agricultural commissioner for purchase or use.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Carrot
UC ANR Publication 3438


  • E. T. Natwick, UC Cooperative Extension, Imperial County
  • D. R. Haviland, UC IPM Program, Kern County
  • C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
Acknowledgment for contributions to Insects:
  • W. E. Chaney, UC Cooperative Extension, Monterey County

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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