By Whitney Cranshaw, Colorado State University Cooperative Extension, Entomology
Pear slugs are strange insects that can damage the foliage of cherry, cotoneaster, hawthorn and even, occasionally, pear. The larvae are usually an olive green, sometimes tinged with a muddy orange with the shiny exterior that makes them reminescent of a recent bird dropping. Presumably, this unusual appearance helps them avoid predation, which is particularly important since they almost always feed on the upper surface of the leaf, well exposed. As they feed they avoid the main veins, producing a characteristic "skeletonizing" injury.
There are two generations of pear slugs. Larvae will complete development in July and move to the base of the plant where they will pupate. Adults of these usually emerge again in late August and September to produce a second cycle of feeding injury.
Pear slug is extremely easy to kill with almost any insecticide. It is also very susceptible to soapy water, although many of the hosts on which it feeds can be injured by soaps. My personal preference is to lightly dust the pear slug larvae with some wood ashes, which turns them into toasty strings within a short period.
Photo: Whitney Cranshaw
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010