Discovering and Exploring the Leaf-feeding Insects in Our Region

Pacific Northwest (PNW) Defoliators

Discovering PNW Defoliators

Unique Diversity in Balance

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.

NAPPO poster

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)

Discovering and Identifying Defoliators in the Region

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

Early larva
Live adult

Identifying defoliators in your backyard is a fun, easy and informative way to learn about and understand them.

Defoliator Biology
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.

It is during larval development that the larva roll, twist, fold, or wad leaves for protection from predators and parasitoids. Next the larva will form a pupa in the leaf shelter they've constructed.

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:

Todd Murray
WSU Skamania County Extension

Hand-rearing Surprises

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

Reports and Surveys

Exotic Defoliators New to Washington State Since 1985
Common Name
Scientific Name
Year Found
Apple ermine moth (AEM) Yponomeuta malinellus Zeller
Cherry ermine moth (CEM) Yponomeuta padellus L.
Apple skeletonizer (AS) Swammerdamia pyrella (Retz.)
Barred fruit tree tortrix (BFTT) Pandemis cerasana (Hubner)
Dark fruit tree tortrix (DFTT) Pandemis heparana (D & Schif)
'Golden' leaf roller (GLR) Acleris holmiana (L.)
Green pug moth (GPM) Chloroclystis rectangulata (L.)
Lesser budmoth (LB) Recurvaria nanella (Hübner)
Apple tortrix (AT) Archips fuscocupreanus Walsm.
Green budworm (GB) Hedya nubiferana (Haworth)
Carnation tortrix (CT) Cacoecimorpha pronubana (Hübner)
European oak skeletonizer (EOS) Carcina quercana (Fabricius)
Straw-colored tortrix (SCT) Clepsis spectrana (Treitschke)
European fruit tree tortrix (EFTT) Archips podana (Scopoli)

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Regional Surveys and Other Discoveries [PDF Format]

1995 Cherry Ermine Moth Survey Report
1995 Exotic Apple Defoliator Survey Report
1996 Apple Tortrix Survey Report
1996 Exotic Apple Defoliator Survey Report
1997 Apple Tortrix Survey Update Report
1998 Carnation Tortrix Survey Report
1998 Straw-colored tortrix (Clepsis spectrana) Survey Report
1998 Port Light Trap Survey Report
2001 Exotic Defoliator Diagnostics Report
2002 European fruit-tree tortrix (Archips podana) Survey Report
2003 Exotic Survey Trap Backlog Report
2004 Light-brown Apple Moth Survey Report
2004 Summer Fruit Tortrix Survey Report
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