Pest description and crop damage Several species of leafroller are pests of hawthorn. These are larvae of moths which use native plants as hosts as well as fruit trees. They all cause similar damage to the trees but differ in their appearance and, more importantly, in their life cycle. The principal leafroller pests of fruit trees can be divided into single-generation moths, such as the fruittree leafroller and the European leafroller, and two-generation moths, such as the obliquebanded leafroller and threelined leafroller. Adults of these species range from fawn-color to dark brown. Distinctive bands or mottling are on the wings. Wingspans range from 0.5 to 1 inch. The larvae of these species are all green caterpillars with a head that will be light brown to black depending on species.
As the name leafroller implies, the larvae roll and tie leaves together for shelter and feeding. Leafroller larvae thrash about violently when disturbed, and may drop from the leaf suspended by a silken thread. The larvae web leaves and flowers together and feed on and tunnel into the unripe and ripe fruit. Feeding on growing points on young plants can promote undesirable branching. Larvae also feed on the surface of the fruit, causing deep, russeted scars.
Biology and life history The single-generation leafrollers overwinter as egg masses on twigs and branches. Eggs hatch in spring as buds are opening, and hatch is completed by petal fall. The larvae feed for 4 to 6 weeks, then pupate in the rolled leaves and emerge as moths in early summer. The overwintering eggs are laid in July.
Two-generation leafrollers overwinter as immature larvae under the bark on scaffold branches of a variety of host plants. Larvae may feed during warm periods in winter, but become active in spring with onset of new growth. They feed for several weeks, then pupate in rolled leaves. Adult moths emerge in late April-May. These lay eggs for the next generation. The next generation hatches in early summer and does the most damage.
Scouting and thresholds Observe early spring growth for rolled leaves and feeding damage on new growth.
Apply when first rollers appear.