What do spruce budworm moths, oak wilt fungus, white-spotted sawyer beetles and Ontario wildfires all have in common? These were just some of the topics addressed at the annual Ontario Forest Health Review conference recently held in Orillia.
This annual sharing of information was hosted by Natural Resources Canada, Forests Ontario, the Ontario Ministry of Natural Resources and Forestry, and the Invasive Species Centre. Speakers were experts in their fields of research regarding all things threatening to our province’s trees.
Our forests are indeed being besieged by numerous stressors, including insects, fungus, drought, fire, and a changing and violent weather pattern (think ice loading and tornado-like winds). A few years ago, this conference would have addressed each of these concerns individually… where are the forest tent caterpillars? How widespread is beech bark disease? Where were the losses due to blow down or ice damage?
This year there was a real blending of information, as ongoing research is showing that, surprise, everything is connected to everything else. This is not to belittle the research, but rather to show our collective maturity at sharing and integrating the discoveries being made by each of these individual efforts.
Let’s start with spruce budworm. This is a moth caterpillar that burrows into the branches of black spruce and cuts off all transportation of nutrients and sap to the needles. The caterpillars get big and fat feeding on the trapped sap while the essential energy-creating needles turn brown and die.
These moths move each year from area to area seeking out fresh stands of spruce to dine on, leaving a large brown trail of dead trees behind them. Much effort is expended in doing aerial surveys to find and map these sites of budworm infestation.
In the ‘old days’, when a new site was discovered an aerial spray program was initiated, with herbicide bombers deployed to strafe the area in hopes of controlling the out-of-control population of moth caterpillars. Save the timber! Save the economy!
Nowadays there seems to be a different attitude prevailing, as post spray surveys revealed a lot more than just the budworm caterpillars were killed off… including many species of birds that depended on these caterpillars for their own survivals. So now the rally cry has shifted from “save the timber for economic gain” over to “how to manage invasives and retain a healthy forest”. Subtle, but welcomed.
Of course all these dead trees make an excellent fuel source for fires. So the shift went from the forestry department’s killing of caterpillars over to the fire suppression gang who were looking at the potentials and severity of risk for a wildfire to get started, and get out-of-hand very quickly.
Research by my fellow Orillian, Kennedy Korkola, working with the University of Toronto, looked the aftermath of a budworm infestation and the ability of the forest to heal itself. Within her project was the awareness of when was the dead forest at its prime for being a fuel source?
You have to realize that a typical healthy spruce forest in central Ontario is thick! So thick and with so many dead lower branches that even just walking through the area is almost impossible. Now add a whole lot of standing dead trees and you begin to realize that ground surveys are a real challenge. But the field crews persevered and the results are quite interesting.
In years one to three after a budworm infestation the ground cover (mosses, ferns, raspberries and herbaceous plants) exploded due to the now available sunlight reaching the forest floor. So these early years have low risk of wildfire as ‘everything is green.’
The next few years saw small shrubs reclaiming the area, once again shading out the forest carpet; and those standing dead trees caused by the budworm were now starting to fall down.
By year nine the forest floor was a maze of dead fallen trees and dead lower branches of the regrowth ... prime fuel source for a wild fire.
So, can this info prevent fires? Nope. But knowing this rate of decay and change in fuel availability can assist fire fighters to plan for the future ... areas of spruce budworm infestation in 2023 will have high potential for fire in 2032. Start planning access routes and evacuation plans now!
The other topic of great concern is the arrival of oak wilt fungus to Ontario. Similar to the spread of the fungus that killed off the mature elm trees in the 1960s, this fungus is carried by insects that naturally visit sappy wounds of oak trees. Then the real trouble begins.
The fungus enters the exposed inner bark as it is scraped off from the foraging beetle. The spores enter the oak tree and infiltrate the entire tree, shutting down sap flow as it plugs the xylem and phloem tubes. Within a year or two the once healthy oak tree is now dead. But wait ... there’s more ... the fungus travels to neighbouring oak trees via their underground interconnected root system.
The bad news is that it has arrived in Ontario (from Michigan) but so far only in three locations (two in Niagara and one in Springwater Township). While the sites in Niagara were somewhat anticipated, the more northerly site was very unexpected by those to study this tree disease.
Work done in Michigan and Wisconsin for the past several decades show that some control of the spread of oak wilt is possible, but the key is early detection and rapid response.
While I appreciate being made aware of these threats to our forests, I must say that my eco-anxiety has not abated. Sigh.