Site Accessibility Information Access Key 1 to Skip to Top Navigation Access Key 2 to Skip to the Three One One link Access Key 3 to Skip to City of Winnipeg Main Menu Access Key 4 to Skip to Left Navigation Menu Access Key 5 to Skip to Content area Access Key 6 to Skip to Right Sidebar content area Access Key 7 to Skip to Footer Links
City of Winnipeg
|  Link to the City of Winnipeg French websiteFrançais  |
COVID-19: City of Winnipeg response and latest updates on City facilities and services COVID-19 : Mesures prises par la Ville de Winnipeg et dernières nouvelles sur les installations et services municipaux
Insect Control

Fall Webworm

What are fall webworms?

Fall webworm

Photo credit:
Katja Schulz under license CC BY 2.0

The fall webworm (Hyphantria cunea) is known for it's webbed nests among hardwood trees in the late summer. Although the webs may look unsightly, the fall webworm will cause no harm to a healthy tree. The fall webworm is an insect native to North America and can be found from Canada south to Mexico. In Canada there is one generation per season, with larvae appearing in late summer through early fall.

What does the fall webworm look like?

Fall webworm

Photo credit:
Ben Sale under license
CC BY 2.0

The adult moth lays her eggs on the underside of leaves. The eggs are deposited in hairy clusters of a few hundred and take a week to hatch. The caterpillars vay in colour from a pale yellow to grey with hairs. They can grow to a length of 35mm and create nests at the end of branches.

The adult moth is white in colour with brown spots, very hairy and may have orange markings on it's legs. It's wingspan is approximately 40mm.

What does fall webworm damage look like?

Fall webworm damage

The fall webworm caterpillar, upon hatching, will create a webbed nest at the tips of branches. They will generally consume the leaves within their nest. If your tree is relatively healthy, the nest will cause no harm to the tree.

How can I control fall webworms?

A tree is normally very tolerant of some defoliation and control efforts are unnecessary when only a few caterpillars are present. If a citizen is concerned they can control them with the use of biological products or chemical pesticides. Biological products like Safer's BTK™ Biological Larvicide contain the active ingredient Bacillus thuringiensis var. kurstaki (Btk) to control caterpillars. Btk is a selective biological insecticide which controls lepidopterous larvae (caterpillars). Btk crystals release a toxic protein when dissolved in the alkaline digestive system of the insect. Btk has to be applied when caterpillars are actively feeding, and applied so that all foliage is thoroughly covered. The caterpillar stops feeding soon after, and dies within five days. Other insects, mammals, birds and fish are not affected by Btk. These products can be found at most local hardware stores. All Pest Control products purchased and used must be registered with Health Canada and contain a Pest Control Product (P.C.P. or PCP) Number on their label.


Last update: July 20, 2020
Contact Us
311
or 1-877-311-4WPG
Media inquiries: 204-986-6000
311@Winnipeg.ca

Administrative Office and Research Laboratory
1539 Waverley Street
Winnipeg MB R3T 4V7

Operations Base
3 Grey Street
Winnipeg MB R2L 1V2
Citizens' Information Service
Search by address
to find out your insect management area.

Was this information helpful?

How can we make this web page better?

Information collected will be used to improve our website. Do not use this form to submit a request for service or information because it will not be forwarded to departments for response. To submit a request for service or information, contact 311.

This form is not intended to collect personal information; however, any personal information you choose to include in your comments is collected by the City of Winnipeg under the authority of section 36(1)(b) of the Freedom of Information and Protection of Privacy Act for the purpose of improving our website and will not be used or disclosed for any other purposes, except as authorized by law. Contact the Corporate Access and Privacy Officer by mail (City Clerk’s Department, Susan A. Thompson Building, 510 Main Street, Winnipeg MB, R3B 1B9) or by telephone (311) if you have any questions about the collection of this information.

Ces renseignements sont-ils utiles?

Comment pourrait-on améliorer cette page Web?

Les renseignements recueillis serviront à l’amélioration de notre site Web. Prière de ne pas se servir de ce formulaire pour soumettre une demande de service ou de renseignements, car la demande ne sera pas transmise au service en question. Pour soumettre une demande de service ou de renseignements, veuillez communiquer avec le 311.

Le présent formulaire ne vise pas à recueillir des renseignements personnels. Cependant, les renseignements personnels que vous choisissez d’inclure dans vos commentaires sont recueillis par la Ville de Winnipeg en conformité avec l’alinéa 36(1)b) de la Loi sur l’accès à l’information et la protection de la vie privée dans le but d’améliorer son site Web et ne seront ni utilisés ni divulgués pour d’autres raisons, sauf dans les cas où cela est autorisé par la loi. Communiquez avec l’agent de l’accès à l’information et de la protection de la vie privée de la Ville par courrier au Bureau du greffier, immeuble Susan-A.-Thompson, 510, rue Main, Winnipeg (Manitoba) R3B 1B9, ou par téléphone au 311 si vous avez des questions sur la collecte de ces renseignements.