Palm leaf skeletonizer—Homaledra sabalella
Larvae of this tiny moth (Coleophoridae) chew the surface of palm leaves. Palm leaf skeletonizer occurs in the Caribbean and Southeastern United States. It has been reported in only a limited area of southern California.
Identification
From a distance, palm leaf skeletonizer damage appears as brown splotches on the leaves. Close examination reveals that caterpillars have fed on the underside of fronds, leaving the veins intact. As feeding expands, the brown splotches enlarge.
The pale-brown or cream-colored larva grows up to 3/5 inch long and feeds hidden with up to 100 other larvae in a tube of dark brown excrement. The gray to yellowish brown, night-flying moths are 1/4 inch long and as with the tiny eggs are easily overlooked.
Life cycle
The adults (moths) live 3 to 10 days, and they do not feed on palm leaves. Female moths lay masses of eggs in pinnae (leaflets) or segment folds of newly expanding leaves.
The caterpillars (larvae) feed on and chew the surface of leaf tissue, causing skeletonization. As larvae feed, they spin a tough, long, silk tube in which and outside of they deposit their fine, brown frass. The caterpillars live in colonies of 35 to 100 individuals within a common tube. They are present throughout the year and can complete five generations per year in warm areas like Florida.
Damage
Palm leaf skeletonizer attacks various palms, including Phoenix and Washingtonia spp. Larvae chew the surface of palm leaves, causing dark discolored blotches on leaves. Infested fronds become dry and brown and eventually die. Infested palms may appear unsightly, but are rarely killed by caterpillar feeding.
Solutions
In an effort to eradicate this pest, palms are monitored and infested fronds are pruned off, sealed securely in plastic bags, and properly disposed of. After pruning off infestations, palms are sprayed with insecticide.
Buy only pest-free plants from reputable local nurseries. Because the palm leaf skeletonizer likely arrived in California on nursery stock shipped from the southeastern United States, be especially vigilant looking for this pest on imported plants.
If you find suspected palm leaf skeletonizers, report this to the county agricultural commissioner. See The Biology and Management of Landscape Palms from the University of California and The Palm Leaf Skeletonizer (PDF) by the University of Florida for more information.
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