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Pretty Destructive: Invasion of the Olive Shootworm

Here in Florida it seems we’re never at a shortage of new pests being introduced into our ecosystem. Most recently, we’ve noticed a new species in our midst, this time joining us from South America: The olive shootworm (Palpita persimilis). It was discovered that this pest had made its way into our backyard when a UF/ IFAS Sumter County Master Gardener found some specimens feeding on her ligustrum tree. Since then, these ornamental pests have been spotted throughout Florida with pockets of infestations being brought to our attention most commonly in the retirement community of The Villages, located in Lake, Sumter, and Marion counties.

Olive Shootworms are actually caterpillars and they look very similar to other native species that share their common green color and measure just under an inch. But these caterpillars are of the variety destined to become moths—not butterflies—and like all caterpillars, they’re voracious herbivores.

Originally a notable pest of olives and privets, here in Florida they seem to prefer ligustrum, though they seem to be widening their palate to other types of ornamental plants as well. While they generally focus on the fresh, tender leaves of new growth, more mature caterpillars can also damage established foliage, skeletonizing leaves and leaving behind unsightly damage.

The Silken Shield

After a sufficient feeding, shootworms spin a cocoon using leaves and silk and remain in this pupal stage for about two weeks. Unfortunately, during this dormant pupal stage, shootworms are protected from insecticide applications. It’s only once the caterpillars emerge from their protective cocoon as winged adults that they’re affected, or even able to be positively identified. In fact, with their orange bands and white wings, they look similar to small butterflies and might even be described as pretty—at least relative to most moths. The bottom moth pictured above is about actual size.

But while these adults can be controlled slightly when treated directly with an insecticide, chemical applications have been deemed fairly ineffective by leading entomologists. Instead, it seems the best defense for now is to remove any pupa and damaged leaves. James Hayden and Lyle Buss of the University of Florida IFAS Extension recommend “trimming foliage to remove eggs and nests […] because any surviving larvae will prefer to consume the resulting new growth.”

Here at Deans, we’ll continue to treat as often as is allowed by product label to minimize their damage, but if you’re currently noticing damage that may appear to be caused by olive shootworms, remember that even after a treatment has been applied—in fact, even if many of the pests have been killed—their damage, webbing, and other signs of their presence will remain visible until the affected foliage grows out or is removed.