Description of the Pest
Spring and fall cankerworms were once major pests of pears when codling moth was controlled with lead arsenate. When organophosphates were used to control codling moth, they ceased to be a problem. The larvae are typical of the group of worms called inch or measuring worms. When mature they are about 1 inch long, green to olive green, with stripes of a different shade of green along the sides.
The larvae are primarily leaf feeders, tending to skeletonize leaves. Occasionally they feed on young fruit by biting deep holes, which later heal, but leave large, scarred depressions similar to the injury caused by green fruitworms. Larvae can be found feeding throughout the tree but tend to be more numerous along center scaffold limbs.
Cankerworms are potential threats in pear orchards where selective materials are used for codling moth control. They may be observed in spring when monitoring for leafrollers during bloom (see SAMPLING AT BLOOM). Follow treatment guidelines for obliquebanded leafroller or omnivorous leafroller.