- The pear sawfly or pear slug is a common pest of fruit trees such as the plum tree. Other trees often infested with this pest include pear, cherry, apple, crabapple, hawthorn, mountain ash and cotoneaster. This pest is referred to as the pear slug while in the larval stage. Larvae are olive-green or black and measure from 1/4 to 3/8 inches in length. Once the larval reach maturity, the slug transforms into a black wasp.
- Adult pear sawflies emerge from the soil from May to June and lay eggs on the leaves of the plum tree. After one to two weeks, these eggs hatch and the larvae emerge. The larvae feed on the leaves of the tree, often causing defoliation. The larvae mature in approximately three weeks. Infestation of the pear sawfly or pear slug does not usually cause the affected plum tree to die, but trees under stress may suffer severe damage.
- The pear sawfly, or pear slug, can cause the leaves they are feeding on to turn brown, to curl and drop early. Leaves are often skeletonized and defoliation of the tree can occur. The larvae usually feed on the lower leaf surfaces first. Injury to plum trees peaks twice during the growing season.
- While injury from the pear sawfly or pear slug does not usually kill the affected tree, severe infestations may require chemical control methods. Applying insecticides labeled for use on caterpillars is usually effective in eliminating and controlling this pest. Non-chemical control methods include spraying trees to knock the larvae from the tree or applying wood ashes. Washing plum trees with soaps and detergents is also effective in controlling light pear sawfly infestations.
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