Fall webworm
Hyphantria cunea
155 host plants
Last updated
Data Coverage 2 of 6 dimensions
Fall webworm creates distinctive web tents on branch tips of alders, cherries, apples, and many other deciduous trees in late August and September. You will see white, silken webs with green, gregarious caterpillars inside feeding on enclosed foliage. Though the tents are unsightly, damage is usually minor and defoliation occurs so late in the season that tree health is rarely compromised. Small trees can be completely defoliated, but established trees typically lose only scattered branch tips.
Remove webs by hand or prune out webbed branches and destroy them to eliminate caterpillars. No other management is necessary for most trees. Bacillus thuringiensis (Bt) can be applied into tents if populations are high on valuable small trees, but application inside the web is difficult. Most trees tolerate fall defoliation without harm since the growing season is nearly finished. Allow natural parasitoids to suppress populations naturally.
Quick Reference
Order
Lepidoptera
Type
defoliator
Host Plants
155
GDD₃₂ Egg hatch/early instar 2nd gen
5,825
Indicator: Crape myrtle Natchez first bloom
Fall webworm Egg hatch/early instar 2nd gen typically begins around 5825 GDD₃₂. As of April 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂, approximately 4644 units before the expected threshold.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,181 | Pre-season | Egg hatch/early instar 2nd gen | 4,644 |
| Seattle / UW | 1,171 | Pre-season | Egg hatch/early instar 2nd gen | 4,654 |
| Kent / Auburn | 1,111 | Pre-season | Egg hatch/early instar 2nd gen | 4,714 |
| Olympia / Tumwater | 1,106 | Pre-season | Egg hatch/early instar 2nd gen | 4,719 |
| Bellingham / Whatcom | 1,101 | Pre-season | Egg hatch/early instar 2nd gen | 4,724 |
| Tacoma / Puyallup | 1,075 | Pre-season | Egg hatch/early instar 2nd gen | 4,750 |
| Sequim / Rain Shadow | 1,070 | Pre-season | Egg hatch/early instar 2nd gen | 4,755 |
Source: UMD IPMnet catalog. Sources: UMD: extension.umd.edu; Wisconsin Extension: Wisconsin Extension. About GDD₃₂ →
Host Plants (155)
Acer crataegifolium Hawthorn, Maple Alnus alnobetula Circumpolar alder group Alnus alnobetula subsp. crispa American Green Alder, Mountain Alder, Green Alder Alnus alnobetula subsp. sinuata Sitka Alder, Wavy Leaf Alder Alnus cordata Italian Alder Alnus glutinosa Common Alder, European Alder, Black Alder Alnus incana subsp. rugosa Speckled Alder Alnus incana subsp. tenuifolia Thinleaf Alder, Mountain Alder Alnus japonica Japanese Alder Alnus rhombifolia White Alder Alnus rubra Red Alder Alnus rubra f. pinnatisecta Cutleaf Red Alder Alnus sinuata Sitka Alder Betula alleghaniensis Yellow Birch Betula davurica Asian Black Birch, Dahurian Birch Betula glandulosa Dwarf Birch Bog Birch, Scrub Birch Betula lenta Sweet Birch, Cherry Birch, Black Birch Betula maximowicziana Monarch Birch Betula nana Dwarf Birch, Bog Birch Betula nigra River Birch, Black Birch Betula occidentalis Water Birch, Western Birch, Red Birch, River Birch, Black Birch Betula papyrifera Paper Birch Betula pendula European White Birch Betula platyphylla Asian White Birch, Manchurian Birch Betula populifolia Gray Birch, Fire Birch Betula pubescens Downy Birch, Moor Birch Betula utilis Himalayan Birch, Bhojpatra, Indian Paper Birch Betula utilis subsp. albosinensis Chinese Paper Birch, Chinese Red Birch Betula utilis subsp. jacquemontii Whitebarked Himalayan Birch Crataegus ambigua Russian Hawthorn Crataegus autumn Crataegus autumn Crataegus columbiana Columbia Hawthorn Crataegus crus Crataegus crus Crataegus douglasii Black Hawthorn Crataegus germanica Medlar Crataegus laevigata English Hawthorn Crataegus lavallei Lavalle Hawthorn, Carrierei Hawthorn Crataegus monogyna Singleseed Hawthorn, Common Hawthorn, English Hawthorn Crataegus phaenopyrum Washington Hawthorn Crataegus punctata Dotted Hawthorn, Flat-topped Hawthorn Crataegus viridis Green Hawthorn,Southern Hawthorn Fraxinus americana White Ash, American Ash Fraxinus anomala Singleleaf Ash, Dwarf Ash Fraxinus excelsior Euopean Ash, Common Ash Fraxinus latifolia Oregon Ash Fraxinus ornus Flowering Ash Fraxinus oxycarpa Fraxinus oxycarpa Fraxinus pennsylvanica Green Ash Fraxinus quadrangulata Blue Ash Fraxinus sieboldiana Siebold Ash, Japanese Flowering Ash, Chinese Flowering Ash Hibiscus syriacus Rose, of Sharon Shrub, Althea Juglans ailantifolia Japanese Walnut, Heartnut Juglans californica California Walnut, Southern California Walnut Juglans cinerea Butternut Juglans microcarpa Texas Walnut, Little Walnut Juglans nigra Black Walnut Juglans regia English Walnut, Persian Walnut Malus 'Indian Magic' Indian Magic Crabapple Malus atrosanguinea Carmine Crabapple Malus brandywine Brandywine Crabapple Malus floribunda Japanese Flowering Crabapple Malus fusca Pacific Crabapple Malus hupehensis Tea Crabapple Malus prairifire Prairifire Crabapple Malus pumila Apple Malus robusta Cherry, Crabapple Malus sargentii Sargent Crabapple, Pigmy Crabapple Malus snowdrift Snowdrift Crabapple Malus transitoria Transitoria Crabapple Platanus acerifolia London Planetree Platanus mexicana Mexican Sycamore Platanus occidentalis American Sycamore, American Planetree Buttonwood Platanus racemosa California Sycamore, Western Sycamore Populus alba White Poplar European White Poplar, Silver Poplar Populus angustifolia Narrowleaf Cottonwood, Mountain Cottonwood Populus balsamifera Balsam Poplar Populus canescens Gray Poplar Populus deltoides Eastern Cottonwood Populus fremontii Fremont Cottonwood, Western Cottonwood Populus grandidentata Bigtooth Aspen Populus nigra Black Poplar Populus tremula European Aspen European Trembling Aspen European Quaking Aspen Populus tremuloides Quaking Aspen Populus trichocarpa Black Cottonwood Prunus americana Wild Plum American (Red) Plum August Plum, Goose Plum Prunus armeniaca Apricot Prunus avium Sweet Cherry Prunus besseyi Sand Cherry, Western Sand Cherry Prunus blireiana Blireiana Plum Prunus caroliniana Carolina Cherrylaurel American Cherrylaurel Prunus cascade Prunus cascade Prunus cerasifera Cherry, Plum Prunus cistena Purpleleaf Sandcherry Redleaf Sandcherry Cistena Sandcherry Cistena Plum Prunus dream Prunus dream Prunus emarginata Bitter Cherry, Wild Cherry, Quinine Cherry Prunus first Prunus first Prunus fruticosa Steppe Cherry, European Dwarf Ground Cherry, Mongolian Cherry Prunus glandulosa Dwarf Flowering Almond Prunus ilicifolia Hollyleaf Cherry, Holly-leaved Cherry Prunus laurocerasus Cherry, Laurel Prunus lusitanica Portugal Laurel Prunus maackii Amur Chokecherry Amur Cherry, Manchurian Cherry Prunus mume Japanese Apricotc Japanese Flowering Apricot Japanese Flowering Plum Prunus newport Newport Flowering Plum Prunus okame Okame Flowering Cherry Prunus padus European Birdcherry Common Birdcherry Prunus prostrata Rock Cherry, Mountain Cherry Prunus sargentii Sargent Cherry, Sargent's Cherry Prunus serotina Black Cherry, Rum Cherry Prunus serrula Birchbark Cherry, Paperbark Cherry, Tibetan Cherry Prunus serrulata Japanese Flowering Cherry Prunus snow Prunus snow Prunus subcordata Klamath Plum, Sierra Plum, Pacific Plum Prunus subhirtella Higan Cherry Prunus subhirtella var. autumnalis Autumn Flowering Higan Cherry Prunus tai Prunus tai Prunus virginiana Prunus virginiana Prunus virginiana var. demissa Western Chokecherry Prunus virginiana var. virginiana Common Chokecherry, Eastern Chokecherry Prunus yedoensis Yoshino Cherry, Somei-yoshino Cherry, Tokyo Cherry Quercus phellos Willow, Oak Rhamnus alnifolia Alder Buckthorn, Glossy Buckthorn, Breaking Buckthorn Rosa acicularis Wild Prickly Rose Rosa gymnocarpa Little Wood Rose, Wood Rose, Baldhip Rose Rosa multiflora Multiflora Rose Rosa nutkana Nootka Rose Rosa pisocarpa Clustered Rose, Swap Rose Rosa rubiginosa Sweetbriar Rose, Eglantine Rose Rosa rugosa Rugosa Rose, Beach Tomato, Sea Tomato Rosa woodsii Woods' Rose Salix alba Salix alba Salix babylonica Weeping Willow Salix caprea Salix caprea Salix integra Salix integra Salix magnifica Magnolia-leaf Willow, Magnificent Willow Salix matsudana Salix matsudana Salix pentandra Laurel, Willow, Bay Willow Salix phlebophylla Skeletonleaf Willow Salix purpurea Purpleosier Alaska Blue Willow Salix scouleriana Scouler's Willow Tilia americana American Linden, American Basswood Tilia cordata Littleleaf Linden Tilia euchlora Crimean Linden Tilia europaea European Linden, Common Linden Common Lime European Basswood Tilia mongolica Mongolian Linden, Mongolian Basswood Tilia tomentosa Silver Linden, Silver Basswood Ulmus americana American Elm Ulmus davidiana David Elm Ulmus davidiana var. davidiana unknown Ulmus davidiana var. japonica Japanese Elm Ulmus glabra Ulmus glabra Ulmus hollandica Dutch Elm, Holland Elm, Hybrid Elm Ulmus parvifolia Lacebark Elm, Chinese Elm Ulmus pumila Siberian Elm Viburnum dilatatum Linden, Viburnum, Linden, Arrowwood