Salt marsh caterpillar damage in strawberries

/ Sarah Zukoff

The salt marsh caterpillar is a common species which feeds on many different species of plants and can be found sporadically on strawberries throughout the year. The defoliation can be quite dramatic in spots when several egg masses hatch at once and the larvae start to feed gregariously. Spot treatments of insecticides (Bacillus thuringiensis, spinosad, or methoxyfenozide) often work on these young larvae before they start to disperse away from each other as they age, but often treatment isn’t necessary since these caterpillars have a lot of natural enemies. The photos below were taken during early spring 2022 in SLO county.

Figure 1. Strawberry plant defoliation by the newly hatched larvae will have small holes and resemble lace. (photo by G. Holmes)
Figure 2. Newly hatched salt marsh caterpillars on the underside of a strawberry leaf. The young caterpillars are known to be in the field one day then disappear the next day as they are one of the few species of caterpillars that can be dispersed by wind! (photo by G. Holmes)
Figure 3. Salt marsh caterpillars come in a wide variety of colors and become much more fuzzy and quite large as they age.
Photo: bugguide.net
Figure 4. Salt marsh moth. (photo by John Flanner)
Figure 5. In order to determine if larvae are still present, look at the holes the larvae cause on the leaves. Older damage will have brownish edges and newer damage will have fresh green edges. Using a hand lens helps distinguish this when you cannot find larvae immediately present on the leaves. In this case, the fresh green edge indicates recent feeding. Resist the urge to spray an insecticide based on damage alone. Often the larvae have either been killed by parasitoids or left to pupate. (photo by G. Holmes)
Figure 6. Look at the above leaf.
Question: Do you think the larvae are nearby and this is new damage?
Answer: This is old damage and the larvae have been gone for more than 48 hours! (photo by G. Holmes)
Figure 7. Salt marsh moth eggs closeup. (photo by S. Zukoff)
Figure 8. Saltmarsh eggs are laid in clusters. (photo by S. Zukoff)

For more information on the salt marsh caterpillar in strawberry visit: https://www2.ipm.ucanr.edu/agriculture/strawberry/Saltmarsh-caterpillar/