Olive Shootworm Caterpillars (Palpita persimilis) Can Seriously Defoliate Japanese Ligustrum
Top 1: The caterpillar creates a lot of frass and webs leaves together loosely. (Pic by Lyle J. Buss). 2nd: Caterpillar frass piles on skeletonized leaf. ( Pic by Doug Caldwell).
3rd pic: The smaller caterpillars skeletonize leaves, creating brown areas and the larger caterpillars consume entire leaves. (Pic by Doug Caldwell).
4th: Cars whiz by brown foliage and denuded Japanese Ligustrums on roadway median in Collier County. (Pic by Pam Lulich).
The moth is sometimes seen flying around the shrubs (Pic by Lyle J. Buss)
I normally think of Japanese privet or ligustrum (Ligustrum japonicum) as not having any chewing insect pests. However, there was an intense outbreak of the olive shootworm in sections of several Collier County medians which went unnoticed until early September in 2019. This chewing pest showed up in Sumter Co. Florida (central Florida) in 2012. Before then there were some scattered reports of this South American native from the early 1980’s. Besides Ligustrum japonicum, it also feeds on olive (Olea europaea) and on Madagascar olive (Noronhia emarginata).
From biology information reported in South America, this moth may have five or six generations per year. The larval stages feed a rather long time from 30 to 45 days and the total life cycle may take 50 days.
So the key is to catch this pest early by scouting the new growth for chewing and caterpillar frass. They really crank it out (see pictures). Consult with your UF Entomology Ornamental Plant specialists to find out what works best. One could start with the “softer” products(less residual and more targeted (narrow-spectrum) specifically for caterpillars) with a Bacillus thuringiensis (BT) product or a spinosad containing product.