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