Bark-eating caterpillar
Hides in a trunk tunnel by day, eats bark by night under a silk-and-frass web — girdling branches and weakening old, neglected trees.
- Pest type
- Bark-boring caterpillar
- Attacks
- Trunk & branch bark
- Worst in
- Old, neglected orchards
- Main risk
- Girdled branches; weakened tree
Overview
The bark-eating caterpillar is a pest of many fruit trees, including guava, pomegranate, citrus and others. The caterpillar bores a tunnel into the trunk or a main branch and shelters in it by day; at night it comes out to feed on the bark, doing so under a protective covering of silk webbing matted with its own frass (droppings) and chewed bark.
This ribbon of silk-and-frass web running along the bark, often around a fork or branch, is the tell-tale sign. By eating the bark, the caterpillar interrupts the tree’s sap flow and can girdle and kill branches; a heavy, long-standing infestation weakens the whole tree and reduces yield. It is especially a pest of old, dense, neglected and poorly-maintained orchards, so orchard hygiene and pruning are an important part of control, alongside directly killing the caterpillar in its tunnel.
How to identify it
- Ribbons or patches of silk webbing matted with brown frass and chewed bark along the trunk and branches, especially at forks.
- A tunnel bored into the trunk or branch under the webbing, where the caterpillar hides by day.
- Eaten, gnawed bark under the web, and in bad cases girdled, dying branches.
- A large caterpillar inside the tunnel when the web is scraped away and the hole probed.
The damage it does
- Bark eaten away under the webs, interrupting sap flow and girdling and killing branches.
- A weakened, less productive tree in a heavy, long-standing infestation.
- Entry wounds and tunnels that can admit other pests and pathogens.
- Damage concentrated and worsening in old, dense, neglected orchards.
When to act
- Inspect trunks and branch forks for the silk-and-frass webs, especially in older orchards, and act on the first webs.
- Deal with the caterpillar in its tunnel directly — the web and tunnel pinpoint exactly where it is.
- Combine control with pruning and cleaning up dense, neglected trees where it thrives.
Organic & cultural control
- Scrape off the silk-and-frass webs to expose the tunnel, then kill the caterpillar mechanically — hook it out or push a wire into the tunnel.
- Prune and open up dense, neglected trees and remove badly-affected/dead branches, since the pest favours such orchards.
- Maintain overall orchard hygiene and tree vigour so trees resist and recover better.
- Keep monitoring older trees, where the pest persists and rebuilds.
Chemical control
- After scraping the web, swab or inject the tunnel/bore hole with a recommended CIB&RC-registered insecticide solution and plug it, to kill the caterpillar inside — the standard targeted method.
- Because the caterpillar hides in the tunnel, this direct tunnel treatment is far more effective than a general bark spray.
- Observe the pre-harvest interval on bearing trees and follow the label.
- Confirm the current recommendation and method for your area with your local KVK or horticulture department.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
There are ribbons of web and frass on the trunk and branches of my guava/pomegranate. What is it?
That silk webbing matted with brown frass and chewed bark, especially at branch forks, is the bark-eating caterpillar. It bores a tunnel into the trunk or branch, hides there by day, and comes out at night to eat the bark under the web. Scrape off the web to find the tunnel, then kill the caterpillar inside — hook it out or treat the tunnel.
How does the bark-eating caterpillar harm the tree?
By eating the bark, it interrupts the flow of sap under the bark and can girdle and kill branches; a heavy, long-standing infestation weakens the whole tree and cuts yield, and its tunnels can admit other pests and rots. It is worst in old, dense, neglected orchards, so pruning and orchard hygiene are an important part of managing it.
What is the most effective way to kill it?
Because it hides in a tunnel, target the tunnel directly: scrape off the silk-and-frass web to expose the bore hole, then hook the caterpillar out with a wire, or swab/inject the tunnel with a recommended insecticide and plug it. This pinpoint treatment is far more effective than spraying the bark generally. Combine it with pruning neglected trees.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.