The Pear Slug (usually call the Cherry Slug in the US) also known as the Cherry or Pear Sawfly is a common problem throughout the South Coastal area of BC. This pest prefers to feed on pear and cherry leaves but will also feed on leaves of plum, quince and occasionally apple. The 5 mm long”slug” like larvae feed on the upper surface of leaves. It is usually a minor issue, however, high populations can defoliate trees.
The Pear Slug overwinters as a pupa in the soil under the tree. Adults emerge in May, mate and the female inserts eggs into tree leaves. Eggs hatch in 10 to 15 days and the larvae feed on the leaves for 3 to 4 weeks then drop from the tree and burrow into the ground to pupate. This first generation is often over looked as damage is usually minor. The second generation emerges in July through early August and feeds into the fall. This generation sometimes caused significant damage. In the early fall this generation drops to the ground and burrows 5 – 8 cm deep in the soil to overwinter.
Adults emerge over an extended period in late April to May. The adult female inserts eggs into leaf tissue, and eggs hatch in 10 to 15 days. Larvae immediately begin to feed on the upper surface of the leaf. After 3 to 4 weeks, they drop to the soil to pupate. Second generation adults emerge in July and larvae from this generation feed in August and September. Most larvae from this generation drop to the ground to overwinter.