A tiny insect is wreaking massive damage in the forests surrounding Powell River. An outbreak of the Douglas fir bark beetle, a cousin of the mountain pine beetle which has destroyed huge swaths of forests in BC’s interior, has already killed many trees in the Sunshine Coast Forest District, with many others showing symptoms of infestation.
Native to BC, the Douglas fir bark beetle is normally a problem in the interior of the province, said Rudi van Zwaaij, area forester with Western Forest Products Inc., but occasionally outbreaks occur on the coast. “It’s endemic in our province,” he said. “It’s always there and when the conditions are right, the population increases and does some damage.”
Adult beetles, which are about the size of a grain of rice, fly and attack trees in spring and early summer. The female beetle burrows under the bark, releasing a chemical, called a pheromone, to attract males. “It basically says lunch time to its friends,” said Martin Plewak, a resource technologist with the ministry of forests, mines and lands. “One will attack, signal it’s a suitable host, mass attack and that’s how they kill off a tree.”
The burrowing adult beetles bring with them a fungus that clogs the conductive tissue of the tree, helping to overcome tree resistance. After mating, the female tunnels upward and lays eggs in the long galleries, which are constructed parallel to the grain of the inner bark. The small white eggs hatch in about two weeks and the second life stage, the larvae, emerge to feed on the tree’s inner bark. This, combined with the growth of the fungus, kills the tree.
Foliage of killed trees turns from green to pale yellow-green to red by the spring of the year following the attack. Red needles may remain on the tree for up to two years after an attack and aerial spotting of these “redtops” helps to determine the extent of an outbreak.
Van Zwaaij was involved in combating an outbreak in 1995 and 1996, mainly around Powell Lake. “We had about 300 pockets of mortality,” he said. “At the time, the markets were high and we were able to helicopter most of that wood out.”
Officials also incorporated a trap-tree program to capture some of the beetle populations, van Zwaaij said, then transported the trees out of the forest to get rid of the beetles. “Here we are again, 15 years later, with a substantial and even bigger outbreak than in 1995.”
The current outbreak started in the last couple of years, said Plewak. “We suspect the buildup was caused due to the wind storms in 2006 and 2007. Factor in the droughty summers we’ve had and you have what we have today, an ideal situation for the bark beetle.”
The Douglas fir bark beetle attacks weak, or stressed, trees, explained Plewak. “It’s a very opportunistic beetle,” he said. “If the tree is showing signs of some form of weakness, whether from drought or root disease—whatever type of sickness it is experiencing—that is the ideal host for the bark beetle.”
Trees that have been blown down, completely knocked over and sitting on the ground are like candy for the bark beetle, Plewak said. “Introduce a high food source for any type of species, whether it be an insect or mammal, and the result is a population explosion.”
The December 2006 windstorm that blew down a massive number of trees in Stanley Park in Vancouver also hit Powell River “really hard,” said van Zwaaij. “In 2007, we harvested 100,000 cubic metres, or 2,000 logging-truck loads of wood that had blown down. But that was only two thirds of the trees that had been blown down. Trees were down all through the forest that we couldn’t find or reach economically.”
Those trees became the host for the bark beetle population to build up, he said. Adding to the number of blown-down trees is the impact from the last two dry summers, said van Zwaaij. “The additional stresses on top of the stresses from the blow down really is an extra trigger that set it off,” he said.
The ministry has conducted some field reconnaissance of the area, said Plewak. In July and August there was an overview flight of the whole Sunshine Coast. Later in October, there was a more detailed survey, trying to pinpoint the exact locations relatively close to Powell River to assess the magnitude of the outbreak. The surveys will also serve as a benchmark to assess if the problem is growing.
“We have hundreds and hundreds of attacks all through the tree farm licence,” said van Zwaaij. “But most of the timber is not accessible.”
The area has the right food source, the age class of the trees the beetles prefer, said van Zwaaij. “We have lots of it, in the 80- to 100-year age class.”
Generally, the bark beetle attacks timber that at the base is larger than 30 centimetres in diametre. “They’re not going to juvenile trees. What they’re trying to go for is that thick bark to insulate them over the winter,” said van Zwaaij.
The strategy to combat the bark beetle involves tricking them by deliberately falling trees, explained van Zwaaij. “The main strategy is to knock the population down, back to its natural levels. The main way we’re doing this is by putting out a cluster of trap trees for the beetles. The preferred tree for a bark beetle to go to is a healthy tree that is freshly blown over or freshly felled.”
Van Zwaaij is identifying locations where there have been beetle attacks. In those areas, they will fell pockets of five to 10 healthy trees, lay them down between now and April, then remove them in the fall.
Another strategy is to use funnel traps in areas where bait trees can’t be used, said Plewak. An ideal spot for funnel traps is along Plutonic Power Corporation’s power line, which runs from the Toba River valley to Saltery Bay. “There are lots of areas there where we can’t pick up wood to salvage it and take it to market. So we’ll use these to try to lure them instead.”
The ministry and industry need the public’s help in combating the beetle, said Plewak. “We do need public support and we do need public cooperation. We do need the public to be vigilant at this time where they buy firewood, maybe taking a look at what they have in their firewood shed. Leave the trap-tree program alone. If you find a trap-tree area, be aware of it and just leave it alone.”
Beetle advice
BC’s ministry of forests, mines and lands has the following advice for residents to help prevent Douglas fir bark beetle damage to property and forests:
• Leave trap trees in the forest alone. Don’t cut them up to use as firewood.
• Never bring firewood with Douglas fir bark beetles in it back to your home, unless you plan to burn it before the following spring.
• Select dry logs for firewood. If you are unsure if the wood has the beetle, peel the bark off and check it.
• If any trees on your property are attacked and killed by beetles, remove and burn them before the following April.
• Never cut and leave green Douglas fir trees on your property.
• If you spot beetles on Crown land near your property, let the forest service know. If you notice your neighbours’ trees have beetles, tell them about it.
