Ravaging Forests

"Our forests are under attack here in Eastern Ontario. We had the forest tent caterpillar. Now we've got the Gypsy moth. And you've got the drought. We're getting  hammered."
"We knew they were here. We just didn't know what numbers there were. It really blew up at this end of the province."
"You can scrape those [egg masses laid by the moths] off the tree and destroy them. You can use soapy water or you can just crush them."
"If people want to take matters into their own hands, that's something you can do, especially if you're a cottage owner. But it's very difficult to do if you have a woodlot."
"Our regional forest health network is watching at what's coming at us from across the border in the States. We're looking at oak wilt. We're looking at hemlock woolly adelgid. The list goes on."
"But right now, it's the Gypsy moth."
Jim McCready, forester, arborist, Eastern Ontario

A Gypsy moth caterpillar. Joe Shorthouse / Postmedia

Mr. McCready is past president of an agency dedicated to protecting and managing forests of the region of eastern Ontario. He has identified the Gypsy moth hatch this year as being particularly acute for the health of the forest mass, a destructive outbreak in a wide swath across the region. Foresters failed to anticipate that this year would be particularly bad for the presence of the moths in huge, destructive numbers. On top of which is the problems generated for the forests by a years'-long drought situation, leaving trees in an already weakened state, vulnerable to the damage caused by the moths.

My daughter lives on a rural property on White Lake, not far from Arnprior. She's seen such infestations before, but her trees have been impacted by the drought situation where no rain of any significance has fallen year after year, even when more than ample rain falls a little further to the north-east where we live, and where there has been no paucity of rain whatever. Here, in the Ottawa area, rain has been a constant throughout the spring, to the extent where the vegetation growth in our nearby forests have been even more vigorous than usual.

Mature female Gypsy moths laying egg masses

Originating in Europe, the
Gypsy moth is one of many invasive species that have devastated local forests. Several years ago it was the Emerald Ash borer beetle that destroyed ash trees. Those that were cut down years back in an effort to stop the advance of the beetle and to protect woodland hikers from the potential of falling trees, are struggling to re-establish themselves, putting out new growth around the ash stumps in a bid to survive.

In 1859 a silkworm breeding experiment took place in Massachusetts with the Gypsy moths. While the experiment failed to succeed, the gypsy moths themselves succeeded in escaping, becoming a destructive pest in an environment where it has no natural predators. The caterpillars can grow to over six centimetres in length, recognized by bristles and a twin row of blue and red dots on their backs. A square metre of foliage will do an individual caterpillar initial to pupation and hatch, when it becomes a grey-brown moth in late summer.

The caterpillars have been present in Ontario since 1969, with intermittent outbreaks. Creeping up trees to feed in the canopy at night, they creep back down during the day making themselves less visible. Forest tent caterpillars, native to the region, feed early in spring and summer when they present an outbreak, so trees have the opportunity to put out a second covering of foliage. With fewer predators compared to the tent caterpillars, the Gypsy moths wreak far more lasting damage.

The only bright spot in defence against their depredations is a virus called baculovirus that they're susceptible to, that destroys the caterpillars from inside out.They lay buff-coloured egg masses on tree trunks providing an opportunity for the less squeamish to scrape them away and destroy them before hatching.