Redhumped caterpillar

Yellow caterpillars with white longitudinal stripes bordered in red, black head capsules, and a distinctive red hump on the fourth body segment appear on cherry, apricot, and rose foliage in Western Washington during April and May. Mature larvae reach 25-35mm and feed in groups, consuming entire leaves and leaving only midveins. Young larvae skeletonize leaf tissue, while older instars can completely defoliate branches.

Look for egg masses on undersides of terminal leaves; removing them prevents damage. Inspect trees weekly for feeding groups. Well-established trees tolerate defoliation, but protect young plants. Bacillus thuringiensis (Bt) spray targets young caterpillars without harming beneficial insects.