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Ugly Nest Caterpillars

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Archips cerasivorana, commonly known as uglynest caterpillars, attack a variety of trees and shrubs in Medicine Hat. They are most commonly found on theUGLY CATAPILLAR branches of Shubert chokecherries, chokecherries, maydays and apple trees. The first sign of an infestation is a few leaves tied together by a dense web. The size of the nest increases as the larvae grow and eventually additional leaves and branches are pulled together until a dense tent-like nest is formed. Inside the nest, the larvae devour most of the leaves and fruit.
Outbreaks may be abundant some years and then scarce for long periods. The damage to the tree is mostly aesthetic and the defoliated branches will regenerate next spring. The nest protects the caterpillars from weather, predators and insecticides.


Uglynest caterpillars produce only one generation per year. The adult moths are typically dull orange and pale brown with a wing span between 18-25 mm. In the fall, females deposit their eggs in flattened clusters on the trunks and branches of host trees. Clusters are initially white and turn black over the course of the winter. The eggs hatch in late spring and the larvae immediately begin feeding and constructing their nest by tying together leaves, branches and fruit. The larvae are most noticeable during the late summer and early fall. Once mature, the larvae pupate in silken cells inside the nest. The adult moths emerge from late July through to September.

  Prevention and Control UGLY CATAPILLARRegularly check susceptible trees in the spring and early summer for the first signs of webbing. If possible, prune the nest from the tree and either burn or dispose in tied plastic bags. Using gloves to physically remove the nest and insects is also an effective control method. Due to the dense webbing of the nests, applying insecticides will likely be ineffective and would be far more detrimental to the natural predators of uglynest caterpillars.