Gypsy Moth Treatments

Hatching has begun. Another season of gypsy moth infestations are ready to plague Southwestern Ontario. There is something you can do about it though. Learn more about gypsy moths and what gypsy moth treatments are available.

What are Gypsy Moths and Why are They a Problem?

Gypsy moths are a non-native defoliating moth species from Europe that was first seen in Ontario in 1969. They go through a lifecycle of egg masses that overwinter on trees which hatch in the early spring. The larvae start small, but quickly grow to late stage caterpillars by May/June. Following a pupae stage, the adult moths hatch and lay eggs for the subsequent year. Like other insect species, they go through periods of population increases; typically gypsy moth outbreaks occur every 7 – 10 years. We are currently in the third season of heavy infestation; a critical time in your tree’s health.

The biggest concern around gypsy moths occurs during the caterpillar stage. Gypsy moth caterpillars are black in colour, hairy with pairs of six (6) red and five (5) blue dots along their backs, and are voracious feeders. They eat leaves off host trees and when heavy infestations occur, can completely defoliate a tree. While most trees can withstand occasional loss of leaves, when they are stripped, especially if this occurs several years in a row, the trees become more susceptible to a host of other problems, like drought, damage from other pests, and poor growing conditions.

What Can You Do About Gypsy Moths

If you had gypsy moths on your property last year, you know how big a problem they are. Not only can they strip a tree of leaves, but they can severely diminish your enjoyment of your outdoor space. No one wants caterpillars dropping on them in the backyard or completely covering your patio, when your yard is one of the few spaces to escape to. The threat to your tree’s health is also nothing to take lightly, as tree removal is not a small task and replacing a mature tree is not without its problems. It takes time for trees to grow, so in the interim you miss out on all the benefits of a large healthy tree—shade, wind and erosion control, homes and perches for birds, insects, and other mammals, and your general enjoyment of them. Better to protect the trees you already have.

The question then becomes what trees are affected by gypsy moths and how can you protect them.

“Hosts range from oak (Quercus), birch (Betula) and aspen (Populus) in the north, to various hardwoods such as sugar maple (Acer saccharum) American beech (Fagus grandifolia) and softwoods such as eastern white pine (Pinus strobus), balsam fir (Abies) and Colorado blue spruce (Picea pungens) in Southern Ontario.”

Ontario Ministry of Natural Resources and Forestry

We have even seen them on other tree species and shrubs, when their preferred hosts are unavailable. Inspect any Oak, Beech, Maple, Birch, Ash, Apple, Crabapple, Poplar, Willow, Linden, Elm, Hawthorn, Spruce (mainly Blue Spruce), and other shrubs you might have on your property.

Gypsy Moth Treatments

CLC Tree Services has a solution. We have been watching the weather forecast and keeping track of growing degree days. Insects are dependent on temperature to move through their life cycle stages. Cooler days mean that those stages get delayed, which is a good thing for treatment. At CLC, we wait for a 90% hatch rate before we start gypsy moth treatments. The cooler temperatures we have experienced this spring means that while hatching has begun, it is not in full swing. You have plenty of time to tackle your gypsy moth problem.

So what can you do? There are several options;

  • Eggs can be destroyed by dislodging the fuzzy masses prior to hatching. The best time is from fall to late winter, into early spring.
  • Once eggs hatch, place a burlap band around the trunk of the tree. This provides a hiding place for the larvae stage during the day. Larvae can then be collected and destroyed (place in soapy water)
  • Sticky bands are effective, but can have adverse effects on non-targeted wildlife. CLC recommends the burlap technique over sticky bands, as they serve a similar purpose and do not harm other creatures.
  • Dipel—a biological insecticide—can be applied as a foliar spray when caterpillars are in the first development stages. If caterpillars are large in size, this application will be ineffective (quotes can be provided for this service)
  • TreeAzin—a bio-insecticide—can be applied as a trunk injection (suitable application for larger trees) to control the larval stage

Currently, we are looking to begin gypsy moth treatments on approximately May 17th. Again, this is dependent upon weather and hatch rates, and we will advise you of when the best time to schedule a treatment is. Currently, we anticipate treatments will be administered until June, possibly into early July. Costs are dependent upon kind and size of tree, but attached is a rough guide to give you an idea of costs involved in treatment.

Diameter at Breast HeightCost (plus, applicable taxes)
30 cm (12 inch)$475.00
50 cm (20 inch)$550.00
75 cm (30 inch)$630.00
100 cm (40 inch)$720.00

If you are looking for gypsy moth treatments for trees in the London and surrounding area, please contact CLC Tree Services at Our Plant Health Care Specialists are closely monitoring the state of gypsy moths in our area and are ready to act, as soon as necessary.

Published by
May 14, 2021 1:18 pm