Ugly Nest Caterpillar

Archips cerasivorana (Fitch)

Identifying Characteristics:

• Adults are a reddish orange coloured moth approximately 1inch (20-24mm) across (with wings spread)
  • Forewings have reddish-brown markings (see Fig 1)
• Larvae are yellowish/light-orange caterpillars of approximately 1inch (20-23mm) in length
  • The head, dorsal part of the thorax (thoracic shield) and posterior (anal shield) are dark coloured (brown or black) (see Fig 2)
  • The abdomen appears spotted due to the presence of a dark spot at the base of abdominal setae (hair-like objects) (see Fig 2)
• Eggs are laid in groups on the host, typically near the base of the trunk of the plant
• Pupae are within the walls of the nest, but move towards the edges before adults emerge (see Fig 3)

Biology & Life cycle:

• Hosts are typically chokecherry; may be found on other cherries, roses, hawthorns, and some species of poplar, trembling aspen, and birch
• Ugly nest caterpillars are univoltine, meaning that they only have one complete generation per year; however, all stages will likely be observed in a single growing season
• This insect overwinters as an egg. Eggs hatch in the late spring
• Larvae feed within the silken nests for several weeks, until they mature and pupate (see Fig 3)
• Adults are active from late June through September

Damaging stages

• The larvae are the only damaging stage of this pest
  • Their feeding on vegetation and silk-nest forming behavior can affect plant health and overall structural and aesthetic appeal (see Fig 4)

Damage – Symptoms and signs:

• The most characteristic sign is the presence of a number of unsightly, webbed nests, wrapping up a number of leaves on one or more branches (see Fig 4)
• Depending on the stage of the nest, the leaves will be green and the nest will contain a number of actively feeding larvae (see Fig 3)
• Over time, the nest will be filled with frass and the debris of different life stages (see Fig 3)
• Entire trees/bushes can be covered with nests (see Fig 4)
• The nests will develop as larvae pull together leaves into groups. They grow larger as the larvae feed and become bigger
• Nests are most likely visible throughout summer, starting in late June

General Management:

• Monitoring for visible nests and then pruning them out is the easiest way to keep a population from building up

Specific Management

• Theoretically, apply a larval-targeted insecticide (contact or ingested; synthetic or biological) to the leaves while the larvae are just emerging, before the nest is fully formed
• If a registered systemic insecticide were available, this could be applied to the plant to reach the feeding larvae within the protected nest

Distribution within Canada:

• This pest is considered to be native to Canada, and can be found in most parts of Canada and Northeastern United States