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Dichomeris marginella

Juniper webworm damage. Photo: Connecticut Agricultural Experiment Station, Bugwood.
Scientific Name: 
Dichomeris marginella
Common Name: 
Juniper Webworm
Growing Degree Days (GDD's): 
1645–1917 GDD's, Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name): 
Chinese juniper (Juniperus chinensis)
Chinese juniper 'Stricta' (Juniperus chinensis 'Stricta')
Common juniper (Juniperus communis 'Depressa')
Creeping juniper (Juniperus horizontalis)
Flaky juniper (Juniperus squamata)
Golden Chinese juniper (Juniperus chinensis 'Aurea')
Irish juniper (Juniperus communis 'Hibernica')
Juniper (Juniperus spp.)
Pfizer juniper (Juniperus chinensis 'Pfitzeriana') *May be resistant.
Savin juniper (Juniperus sabina) *May be resistant.
Swedish juniper (Juniperus communis 'Suecica')
Insect Description: 

The juniper webworm is a non-native insect that originates from Europe, first reported in the US in 1910. One generation occurs per year, with adult moths active in June and July in the northern parts of its introduced range (points south may have moth activity in May and June). Moths have a life span of approximately 15 days. Adult female moths are capable of producing 50-130 eggs (some sources say as many as 200). Moths have coppery brown forewings outlined with a band of white on the front and rear margins of the forewings, with approximately 0.6 inch wingspans. This helps identify them, along with their correlation with Juniperus hosts. Females lay their eggs (which are white when first laid, but then turn yellow, orange, and finally red as they develop) singly on leaves or near current year's shoots. Eggs are broad and rounded, sculptured, and approximately 5 mm. long. The newly hatched larvae begin life as leaf miners, mining many leaves before beginning to feed on leaf surfaces. Once they leave the leaf mining phase, they begin to construct tubes made of silk around their feeding sites. Early infestations are easily missed due to the behavior of young larvae to inhabit the inner foliage of its hosts first. By the fall, nests including multiple larvae (3-5) may be found webbed together. The juniper webworm overwinters as a caterpillar, in the 5th, 6th, or 7th instar. Feeding begins again the following spring. At that time, the majority of the webbing is produced by the caterpillars. Caterpillars are easily hidden in the naturally dense foliage of their hosts, in addition to being concealed in their webs. Mature caterpillars reach approximately 3/4 inch in length and are tan with brown stripes, a black head, and a dark colored thoracic segment just behind the head. Once mature, larvae pupate and adult moths emerge to begin the cycle again. Pupae are light to dark reddish brown and approximately 1/4 inch in length and pupation occurs in whitish silken cases.

Damage to Host: 

Foliage of juniper, especially upright forms, is impacted. Eventually, foliage damaged by the caterpillars will be webbed together and browned; however, early infestations may be mistaken for spider mite damage when larval feeding causes needles to yellow. Eventually foliage will brown and entire plants may be killed.


Search susceptible hosts for off-colored needles. Pull apart the thick branches and search for webbed together leaves filled with frass and tan colored caterpillars. Search the inner parts of the tree or shrub first. Look for adults laying eggs in June and July. Adults, if present, will fly out of host plants if jarred or shaken. 

Cultural Management: 

Plant resistant species when possible, such as Pfitzer and Savin junipers. Prune out and remove dead branches, where possible.

Natural Enemies & Biological Control: 

Several natural enemies are reported for the juniper webworm. However, some of the most notable include a species of predaceous mite (Pyemotes tritici) and several parasites including: Tetrastichus spp.Catolaccus aeneoviridisItoplectis conquisitorPimpla (Coccygomimus) aequalis, and Bracon gelechiae. Schaffner (1959) also reports hymenopteran parasitoids including Agathis acrobasidis, Bracon spp., Campoplex spp., Hyposoter spp., Pimpla aequalis, and Tetrastichus coerulescens.  

Chemical Management: 

Abamectin (NL)

Acephate (NL)

Azadirachtin (NL)

Bacillus thuringiensis subsp. kurstaki (NL)

Bifenthrin (NL)

Carbaryl (L)

Chlorpyrifos (N)

Cyantraniliprole (NL)

Cyfluthrin (NL)

Deltamethrin (L)

Flonicamid+cyclaniliprole (N)

Gamma-cyhalothrin (L)

Horticultural oil (eggs) (L)

Indoxacarb (L)

Lambda-cyhalothrin (L)

Malathion (L)

Permethrin (L)

Pyrethrins+piperonyl butoxide (L)

Spinetoram + sulfoxaflor (N)

Spinosad (NL)

Tebufenozide (NL)

Trichlorfon (L)


Active ingredients that may be applied systemically include: acephate (injection) and azadirachtin (injection, soil drench).

When used in nursery settings, chlorpyrifos is for quarantine use only.

Contact insecticides must get past the webs and onto the larvae in order to effectively manage these caterpillars.

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: .