Caterpillars Eating Your Trees in Vaughan

A tree full of caterpillars looks like a disaster, and the sound of frass, their droppings, falling on a deck is hard to forget. The good news is that most of the caterpillars that hit Vaughan trees eat the leaves and leave the tree alive. The job is to work out which one you have and whether your tree can handle it.

The Usual Suspects

Three caterpillars do most of the leaf damage in Vaughan.

Spongy Moth

Spongy moth used to be called LDD or gypsy moth. Ontario had a big outbreak that peaked between 2020 and 2022. The caterpillars are hairy, with pairs of blue and red dots down the back, and they feed in May and June. They love oak but eat maple, birch, apple and many others. In heavy years they strip whole trees and then move to spruce and pine.

The females lay tan, fuzzy egg masses on bark, fences, firewood and the underside of patio furniture. Each one holds hundreds of eggs.

Eastern Tent Caterpillar

These build white silk tents in the forks of branches early in spring, often on wild cherry, apple and crabapple. They stay in the tent at night and go out to feed during the day. They are done by early summer and the tree usually leafs out again.

Fall Webworm

Fall webworm makes loose webs that wrap the ends of branches in late summer. Because they feed so late, the tree has already done most of its growing for the year. They look bad but cause little lasting harm.

Will Your Tree Be OK?

A healthy hardwood that loses its leaves in June usually puts out a second flush by mid-summer. That costs it stored energy. One year is fine. Problems start when:

• The tree loses its leaves two or three years in a row
• It was already stressed by drought, root damage or construction
• It is an evergreen, which can’t replace needles the same way
• Dead branches show up in the crown the following spring

What You Can Do Yourself

• Scrape egg masses. From fall to spring, scrape spongy moth egg masses off bark and fences into a bucket of soapy water. Leave them a couple of days before you throw them out. Smashing them on the ground doesn’t kill all the eggs.
• Band the trunk. In late spring, a strip of burlap tied around the trunk and folded over gives older caterpillars a place to hide by day. Check under it each afternoon and knock them into soapy water.
• Pull out tents. Tent caterpillar nests within reach can come out with a gloved hand or a stick on a cool morning, when the caterpillars are inside. Never burn a nest on the tree.
• Water in a dry summer. A tree regrowing its leaves needs water. A slow, deep soak once a week in a drought helps it more than anything else.

Spraying is a licensed applicator’s job, and we don’t spray or inject. For a big tree with a heavy infestation, a licensed applicator is the right call.

Caterpillars in Vaughan

The oaks in Kleinburg and around the Humber valleys took the worst of the spongy moth years, along with the mature maples on older Woodbridge and Thornhill streets. On newer lots in Vellore Village and Sonoma Heights, we mostly see tent caterpillars on ornamental cherries and crabapples. Fall webworm turns up all over the city in August and September.

Normal pruning of your own tree needs no City permit. If a tree has died after years of leaf loss and the trunk is 20 cm or wider at 1.37 m, a permit applies, with no fee for a dead tree. Boulevard trees belong to the City; call Vaughan Public Works at 905-832-8585.

Cleaning Up After a Bad Year

A heavy caterpillar year leaves a mess: frass on decks and cars, chewed leaf bits in the eavestroughs, and empty egg masses on fences and siding. Hose the frass off before it stains, and check the eavestroughs before fall rain. Walk the yard in late fall and again in early spring and scrape any new egg masses you find, including on firewood piles, sheds and the underside of outdoor furniture. Firewood moved from a hard-hit area can carry egg masses to a new yard, so burn what you have at home rather than bringing it to the cottage.

The spring after, watch which branches leaf out. Branches that stay bare are dead, and dead wood over a deck or roof is what we would take out first.

When to Call Us

Call or text (289) 444-0864 if a tree stays bare into July, if dead branches appear after a bad caterpillar year, or if the tree hangs over the house and you want it checked. We come out the same day and give you a firm price.

A stressed tree often needs its deadwood taken out so it can recover and so dead limbs don’t fall. Our tree trimming and pruning page explains what we do. If the leaves are turning brown rather than disappearing, read why leaves turn brown in summer.