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Bucculatrix ainsliella

Oak skeletonizer larvae, cocoons, and damage. Photo: James Solomon, USDA Forest Service, Bugwood.
Scientific Name: 
Bucculatrix ainsliella
Common Name: 
Oak Skeletonizer
Growing Degree Days (GDD's): 
448–707 GDD's (Beginning of June), 1798–2155 GDD's (Beginning of August), Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension; Robert Childs, UMass Extension.)
Host Plant(s) Common Name (Scientific Name): 
Chestnut (Castanea spp.)
Oak (Quercus spp.)
Pin oak (Quercus palustris)
Willow oak (Quercus phellos)
Insect Description: 

The oak skeletonizer is a native species of New England and elsewhere in the eastern United States and parts of Canada. Deciduous oaks and chestnut are hosts for this insect. The adult moth of this species is typically present by late May, with females laying their eggs on the undersides of host plant leaves. Eggs hatch and larvae (caterpillars) feed by skeletonizing the leaf to the extent that it becomes translucent, with only the leaf veins left intact. Pale yellow or green tinted larvae are fully grown when they are approximately 7 mm. in length. If disturbed, the larvae will drop from the tree on a silken thread. Caterpillars spin small, flat webs to molt in between instars. For the last molt of the caterpillar, they will form white, ribbed cocoons on leaves, branches, and twigs within which they will eventually pupate. The insect may overwinter as a prepupa in these cocoons, and eventually pupate the following season prior to emerging as an adult. In the warmer parts of its range, it is possible that this insect has 2 generations per year. Occasionally, this insect has a large outbreak population. For example, in 1971 in New York, trees were damaged by this insect by July and a second generation was found by September. In 1959 and 1960, two generations per year were observed in Michigan (Gibbons and Butcher, 1961).

Damage to Host: 

Foliage of the red oak group is skeletonized by this species. Leaves become translucent and eventually dry out. Heavily attacked foliage will appear lacey from the skeletonizing. Occasional outbreaks can cause damage over a large area, and repeated years of defoliation can cause a reduction in host plant growth. Occasionally, part of the tree crown may be killed by the activity of this insect. However, the oak skeletonizer is often found in low level, non-damaging populations and their presence can be tolerated. In those years, chemical intervention is not necessary.


Visually monitor for the activity of this insect in late May or early June (first generation). Look for skeletonized host plant leaves and eventually the characteristic white, ribbed cocoons.

Cultural Management: 

Rake up fallen, infested host plant leaves and destroy. This will remove the cocoons. 

Natural Enemies & Biological Control: 

Because of the fluctuation in oak skeletonizer populations from year to year, and collapses following occasional outbreaks, parasites and predators are assumed to be impacting their populations. However, little is known about the specifics regarding these natural enemies at this time. Schaffner (1959) reports the following hymenopteran parasitoids from oak skeletonizer samples collected in Massachusetts and New York: Bucculatriplex bucculatricisChrysocharis spp., Cirrospilus cinctithorax, Cirrospilus flavicinctus, Eurytoma solenozopheriae, and Pnigalio maculipes.

Chemical Management: 

Azadirachtin (NL)

Bacillus thuringiensis subsp. kurstaki (NL)

Bifenthrin (NL)

Carbaryl (L)

Chlorpyrifos (larvae) (N)

Flonicamid+cyclaniliprole (N)

Gamma-cyhalothrin (L)

Horticultural oil (eggs) (L)

Lambda-cyhalothrin (L)

Neem oil (NL)

Pyrethrin+sulfur (NL)

Pyrethrins+piperonyl butoxide (L)

Spinosad (NL)


Two applications at 10 day intervals may be needed for heavy infestations.

When used in a nursery setting, chlorpyrifos is for quarantine use only.

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: .