The dreaded Gypsy Moth Caterpillars are back and we asked one local expert what is to be expected from the pest this summer.
Until recently, many people were not even aware of the existence of Gypsy Moth Caterpillars, which in small numbers have gone quietly under the radar. When the population exploded last year, it was one more thing people had to deal with, on top of a pandemic.
According to County of Simcoe forester Graeme Davis, there are a lot of variables at play when it comes to predicting the eventual collapse of the Gypsy Moth Caterpillar population.
“There’s enough uncertainty that we can’t guarantee what is going to happen this year, that’s for sure,” said Davis.
Regardless, plenty of egg masses laid last year throughout the county mean we are in for plenty of aggravation from the caterpillars, which are currently very tiny put definitely on the move. The caterpillars have left their egg masses and can already be seen swinging through the air on their invisible silk strings, which they use to disperse to their feeding grounds in the tree canopy. As they feast and grow, their waste – called frass – rains down on people below.
“Just based on an egg mass count, indications are that there will be quite a large hatch again this year, however – and there’s always a large but – there are many other factors at play here which will determine just what kind of a season we have with Gypsy Moth,” said Davis.
“These things are always cyclical. They will go through a boom and bust cycle and the big question is whether this year will be another complete boom year or whether it will be the bust.”
One thing that would have helped to reduce the population is winter temperatures of -20ºC and that didn’t happen.
However, the egg masses are threatened by parasites, a virus and a fungus that will eventually lead to the collapse of the population, although the timing could differ across the county.
“There is quite a high likelihood that that virus could take hold and start to kill off the caterpillars shortly after they hatch and could really reduce the overall impact of the Gypsy Moth. The problem is we can’t say that for certain,” said Davis.
Homeowners may have tried to remove the egg sacks but in some areas they are just too plentiful and it is almost impossible to get to all of them, especially if they are high up in the trees. Davis said the egg masses are also on the ground and other hard-to-see places, so eradicating them can be very tricky, if not impossible.
The only other course of action is to have the trees treated with a bacterial insecticide, either by injection or aerial spray, which can be costly. The county does not take any action against the caterpillars, because although they are pesky to people trying to enjoy the outdoors, and they do feast aggressively on leaves, most trees fully recover from an infestation so they are not considered a serious threat to the health of the forest.
“Although you will get some trees that certainly will be stressed, especially if they’re completely defoliated. Most hardwood trees for example, will leaf out a second time and although it does impact their reserves in most cases an overall forest area, the longer term impacts will be quite modest,” said Davis.
“It’s a really substantial nuisance for us. I think even more so right now with everyone spending so much time at home and with everyone being cooped up all winter, we’re going to want to get outside and this is not something that’s conducive to us enjoying [our properties].”