Leaf-eating insects in our region include a diverse mix of native species and species introduced from other parts of the world. This mix of species is mostly accidental, from insects hitch-hiking with people, food, and flowers; and began with the first immigrants from around the world.
In recent years, growing international trade of foreign plant products and expanding global travel have created new pathways for the arrival of exotic species. In the last two decades more than a dozen foreign defoliators have been introduced to our region, some of which are now the most common and abundant in some areas. (More)
Fortunately, the increasing diversity of defoliators in the region has seldom resulted in serious or chronic defoliation or other major problems, although that potential exists and may increase with climate-change and weather-related stresses on plants here. In large part, both the native and exotic defoliators are controlled by bird and insect predation and an equally diverse complex of parasitoids. A 1999 survey of defoliator parasitoids found that the 14 most common defoliators were attacked by 46 parasitoid species, including one exotic species new to North America and one new to science. (More)
Regional and local defoliator surveys providing information for this web site have been conducted by the authors since 1994, funded by supporting state agencies and the United States Department of Agriculture APHIS. Detailed reports are available for specific surveys here and much more defoliator information is available from other contributor web sites and regional extension offices. (More)
Discovering and Identifying Defoliators in Your Backyard
Identifying defoliators in your backyard is a fun, easy and informative way to learn about and understand them.
Understanding the biology of defoliators is helpful when learning to identify the various species since the adult stage is not always identifiable. Defoliators pass through four main life stages; eggs, larva (caterpillar), pupa (chrysalis or cocoon) and adult.
Adult defoliators lay their eggs on the host (food plant), and after hatching the larvae will feed on the leaves for up to two weeks. This is when all defoliation feeding occurs.
In the early larva stage most defoliator caterpillars are a light green with a dark head. As they grow the colors and patterns develop in the last larval stage which make it somewhat identifiable.
The adult defoliator emerges (ecloses) from the pupa within two to three weeks. Most defoliators spend the winter as eggs or small larva. Most complete one life cycle (univoltine) per year, although a few produce two or more generations (multivoltine) each year. With few exceptions, adult moths do not feed on plant tissue, but sip flower nectar or other liquids.
Hand Rearing Defoliators
Rearing larvae or pupae to the adult stage is the best way to identify defoliators. The best time to rear larvae is in early spring, especially May and early June when larvae are full grown and easy to find. They are close to their pupa stage and will emerge as adults within weeks of collecting. Finding and rearing pupae is even easier as adults eclose (emerge) within 10-14 days.
All you need to rear a larva or pupa is a container with a lid and the leaves you find the larva or pupa on. Set them aside and wait a few weeks.
When the adult ecloses (emerges) it is distinctive and can be identified by comparing it to the images of adult moths for identification. If an identification can't be made, send the moth or photograph to:
WSU Skamania County Extension
What if it isn't a moth that emerges?
In many cases what will emerge isn't the defoliator. If a fly or wasp emerges from the larva/pupa, the larva or pupa has been destroyed by a parasitoid.
Exotic Defoliators New to Washington State Since 1985 Common Name Scientific Name Year Found Apple ermine moth (AEM) Yponomeuta malinellus Zeller 1985 Cherry ermine moth (CEM) Yponomeuta padellus L. 1993 Apple skeletonizer (AS) Swammerdamia pyrella (Retz.) 1994 Barred fruit tree tortrix (BFTT) Pandemis cerasana (Hubner) 1994 Dark fruit tree tortrix (DFTT) Pandemis heparana (D & Schif) 1994 'Golden' leaf roller (GLR) Acleris holmiana (L.) 1994 Green pug moth (GPM) Chloroclystis rectangulata (L.) 1994 Lesser budmoth (LB) Recurvaria nanella (Hübner) 1994 Apple tortrix (AT) Archips fuscocupreanus Walsm. 1995 Green budworm (GB) Hedya nubiferana (Haworth) 1995 Carnation tortrix (CT) Cacoecimorpha pronubana (Hübner) 1997 European oak skeletonizer (EOS) Carcina quercana (Fabricius) 1997 Straw-colored tortrix (SCT) Clepsis spectrana (Treitschke) 1998 European fruit tree tortrix (EFTT) Archips podana (Scopoli) 2000