The Grapeleaf Skeletonizer: A Hidden Pest in Your Garden

Introduction

Have you ever noticed your grapevines mysteriously losing their leaves? If so, you might be dealing with the grapeleaf skeletonizer (scientific name: Harrisina americana). This common species can be found throughout Florida and the eastern half of the United States. In this article, we’ll explore the identification, life history, damage, and management of this pest.

Identifying the Grapeleaf Skeletonizer

Adult grapeleaf skeletonizer moths are easily recognizable by their black coloration and distinctive yellow or orange collar. The antennae are pectinate in both males and females, with the male’s antennae being more plumose. The forewings are four times as long as they are wide and larger than the hind wings. The abdomen of the moth is curled upwards and expands into a fan-shaped, bilobed caudal tuft. The wingspan ranges from 22 to 28 mm, and the length of the moth is 8 to 12 mm.

Adult grapeleaf skeletonizer
Image: Adult grapeleaf skeletonizer

The larvae of the grapeleaf skeletonizer are yellowish with black spots or bands. When mature, they reach a length slightly over 1/2 inch. Eggs are lemon yellow and cylindrical-oval in shape, laid in clusters on the lower surfaces of leaves.

Grapeleaf skeletonizer larvae
Image: Grapeleaf skeletonizer larvae

Understanding its Life Cycle

The grapeleaf skeletonizer has an interesting life cycle. According to research, the average length of its life cycle is about 66.7 days, with a minimum of 53 days. The egg stage lasts about eight days, the larval stage around 40 days, and the pupal stage about 15 days. The adult moth only lives for approximately 3.5 days.

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Moths can be observed in Florida from March to September. They are diurnal and nocturnal, but mainly active around dawn. The grapeleaf skeletonizer spends winter in the pupal stage, and the senior author has seen egg clusters as early as April. There are at least two, and potentially three, generations of grapeleaf skeletonizers per year in Florida.

Damage and Detection

Grapeleaf skeletonizer larvae can cause significant damage to grapevines. The initial symptoms include the appearance of brown, necrotic, skeletonized leaf tissue, as the young larvae eat some but not all layers of the leaf. As they mature, the larvae devour the entire leaf, leaving only a few large veins. One unique characteristic of these pests is their gregarious feeding behavior, where they feed in row-like groups. However, as they reach maturity, they tend to disperse as isolated individuals or in small groups.

Grapeleaf skeletonizer damage
Image: Damage caused by grapeleaf skeletonizer larvae

Hosts and Management

The grapeleaf skeletonizer primarily feeds on wild grapes and Virginia creeper. However, it also targets cultivated grape varieties, especially the more tender and exotic ones. If you have a vineyard receiving regular treatment for other grape pests, you are less likely to face issues with grapeleaf skeletonizers.

One effective management method is using Bacillus thuringiensis, a bacterial pesticide that specifically targets caterpillars. Handpicking the larvae in small areas can also be an efficient treatment, given their gregarious feeding habit. When the larvae are noticed on the foliage, they should be removed immediately as they tend to cluster together. Delaying treatment until the larvae have dispersed into individual or small groups would require more labor. Additionally, practicing clean culture by removing cocoons from the leaves and trash at the bottom of vines is recommended.

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Conclusion

The grapeleaf skeletonizer may be a hidden pest in your garden, causing damage to your grapevines. By understanding its identification, life history, and management techniques, you can effectively combat this pest and protect your beloved grape plants. Stay vigilant and take action to ensure the health and productivity of your grapevines.

For more information about grapeleaf skeletonizers and other gardening tips, visit the Ames Farm Center website.

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