The Healthy Forest Partnership, a coalition of industry, university and government participants, in consultation with First Nations communities, has been combating the latest budworm threat since 2014, using monitoring, detection and treatment protocols to get ahead of a Quebec-based infestation spreading towards the spruce and fir forests of New Brunswick.
The results to date have been so dramatic, it is now possible to visually detect the Quebec-New Brunswick border from the air due to heavy defoliation on the Quebec side versus none visible in New Brunswick.
The numbers tell a surprising and unexpected story. Based on an intensive sampling of larvae, spruce budworm populations across northern New Brunswick showed over a 90 per cent reduction in 2018. Only about 500 hectares of defoliation were detected last year in New Brunswick, compared to over 2.5 million ha in the adjacent lower St. Laurent-Gaspésie areas of Quebec. In 2018 the project treated 220,000 ha in northern New Brunswick. In 2019, only about 10,000 ha of forest will be treated.
David MacLean, professor emeritus of forest ecology at UNB and lead scientist for the early intervention project, is being cautious about results to date, but there is no doubt they are extremely promising.
“When we started this, we figured it was worth a try but it was a long shot,” says Dr. MacLean. “After five years of being in it, we can’t really claim it works yet but it certainly seems to be working. The results are positive.”
The promising results have been noticed. The early intervention strategy, operating under the umbrella of the Healthy Forest Partnership, has been approved for $75 million of continued funding from federal (Natural Resources Canada) and Atlantic Canada provincial governments and industry for 2018-2022. The project was originally funded with $18 million from 2014-18, contributed by the Atlantic Canada Opportunities Agency, Natural Resources Canada, industry and the New Brunswick government.
The Healthy Forest Partnership, through the Government of New Brunswick, has been consulting with both the Wolastoqey and the Mi’kmaq peoples on the research treatments taking place in northern New Brunswick. This includes discussions and information sharing at meetings and in communities.
The budworm intervention strategy is breaking new ground. It is the first attempt at area-wide management (within the funded trial area of Atlantic Canada) of a native defoliating insect.
Forest scientists and industry representatives in New Brunswick had been watching the progress of the budworm infestation that began in northern Quebec around 2004-05 and began spreading south and eastward. By 2012, the budworm was eating its way across the Gaspé and scientists and forestry companies in New Brunswick wondered what could be done to manage the budworm differently.
In the past, the strategy was always to spray insecticides to keep valuable stands of trees alive. This is still the approach in Quebec where it is now too late to consider early intervention with over 8 million ha of defoliation. The early intervention strategy detects very low-level populations when they are just starting to rise - the threshold is seven overwintering larvae per branch - and eliminating them with biological insecticides to reduce the local populations. Dr. MacLean says it’s a bit like a game of whack-a-mole.
“The early intervention strategy is to start earlier, use biological insecticides, target areas that we are calling hotspots where populations are starting to rise, and treat them much earlier than we would have in the past,” he says.
Part of the reason the New Brunswick team thought this might work was research done in Quebec over the last five to 10 years that found when budworm populations are low and there aren’t many around, the mating success of female moths can be low. The female sends out a pheromone plume, kind of like a sex attractant perfume, that the male uses to find her and mate. The female can lay up to 200 eggs.
“When there are not as many around, not everyone gets mated because they don’t find each other,” says Dr. MacLean. “So that was one biological mechanism that suggested if we could catch this slow but rising population and drive it back down, maybe it would stay at low levels.”
The first step in the intervention program involves intensive monitoring and early detection of low-level increases in budworm populations before substantial defoliation occurs. This involves sampling of the tiny overwintering spruce budworm larvae on branches at about 2,000 sites across New Brunswick each year. Among other things, the team is testing the use of drones as part of its early detection arsenal.
In the second step, there is a target-specific application of biological insecticides (Bacillus thuringiensis or tebufenozide) to locations with rising budworm populations higher than seven larvae per branch. Dr. MacLean says the approach focuses on controlling low-density, growing populations along the leading edge of outbreaks as a way of containing spread.
“The first populations were in the very northwest part of the province, right up against the Quebec border,” says Dr. MacLean. “2015 was the first year that we forecast defoliation, in an area south of Campbellton. We sprayed about 15,000 ha that year.”
In 2016, about 60,000 ha were treated; about 150,000 ha in 2017 and about 200,000 ha in 2018.
“They typically have not been the same areas year over year, but they have been adjacent ones,” says Dr. MacLean. “We have found the areas that are being treated with insecticide are effectively bringing the populations down in the spray block. We usually do not have to treat them the following year.”
So why, after several years of steadily increasing budworm populations in northern New Brunswick, did the numbers suddenly and unexpectedly decline, to the point where just 10,000 ha are forecast to be treated this year?
“We don’t really know why yet,” Dr. MacLean says. “There is a possibility it could be the weather, but that’s not likely the case - the budworm larvae seem quite resilient to that. It might be natural enemies. There is quite a complex food web and a whole range of parasitoids that parasitize the budworm - something like 75 different species. So it may well be that, possibly assisted by the early intervention treatments. Or it could be disease build-up in the populations ... Research into the causes is continuing.”
Dr. MacLean says forest scientists are being very cautious about claiming that it (early intervention) is definitely working, “but results are certainly positive so far.”
