SEELEY LAKE – With the onset of summer come bugs and other diseases that have been continually affecting trees in area forests for decades. Montana Department of Natural Resources and Conservation (DNRC) Forest Pathologist Katie McKeever shared some of the trends and treatment options for beetles, budworm and black pineleaf scale at the annual log seller, contract logger and landowner meeting hosted by Pyramid Mountain Lumber, Inc. May 5.
Western Spruce Budworm
Western spruce budworm was detected in 890,194 acres in 2016. While budworm does not outright kill mature trees, chronic, heavy damage can kill understory trees or predispose mature trees to Douglas-fir beetle.
McKeever said there has been an eastward trend with Gallatin, Judith Basin, Madison, Meagher and Park Counties being hit the hardest in 2016. She said the shift was due to a cool, wet spring in the western counties knocking the budworm back, while the eastern counties of the state had normal springs fostering good growing conditions for budworm.
McKeever said managing for a single story canopy can be a more long term approach to controlling budworm populations.
“Budworm larvae send out little silk streams and they loom down from the infested upper canopy. They land on the lower canopy and that is where they can perpetuate the disease cycle. If they land on the forest floor they get eaten,” said McKeever.
Another management option is mixing in lodgepole and ponderosa pine throughout a stand. Even though the name is specific to spruce, it will affect Douglas-fir and subalpine fir. When populations are large enough it will spill over into spruce and larch.
“Mixing in pines will break up that continuous host material and put some green on the landscape,” said McKeever.
McKeever said trees can be sprayed with various chemicals and biological control agents including Carbaryl (Sevin) and Bacillus thuringiensis subsp. kurstaki (BTK). While these treatments will knock back the budworm, McKeever called these treatments bandages “ [because] you will continue to have problems in subsequent years. Silvicultural management in conjunction with some of the sprays can be useful.”
Mountain Pine Beetle
The Mountain Pine Beetle outbreak started in the late 1990s. McKeever said the peak of the outbreak was in 2008-2009. In one year, one million acres were affected. Six million acres were infested before finally starting to taper off around 2015. In 2015 only 174,000 acres were affected and that dropped to only 10,765 acres in the state in 2016.
“We are pretty much calling this mountain pine beetle thing over and done,” said McKeever. “It is good news that it is over and done but bad news because it means that it has come through and taken out all of our suitable diameter pines.”
While mountain pine beetle is no longer a big concern in low-elevation production forests, McKeever said it is still a concern in the high-elevation forests. The pine beetle affects white bark pine and limber pine, two ecologically important species in the high-elevations.
McKeever said they are seeing “Ghost forests” where the trees are dying out and they are not regenerating. That is a concern that the DNRC has recognized and is shifting resources and research to restoration efforts.
Ips Pine Beetle
Ips pine beetles or pine engravers are a problem in four to five inch diameter trees and often go into slash piles. They are not aggressive with healthy, vigorous trees. However, McKeever said that if populations are big enough, they can produce big brood populations. If there are no other small diameter materials for the next generation, they will infest the surrounding stand. McKeever said top kill in large trees is a good indicator of Ips beetles in a stand.
McKeever said slash management is the best solution to keeping Ips in check. Creating and leaving green slash piles in early spring and through the summer will attract Ips.
“Burn it or do something to get it off the property,” said McKeever.
Piling late in the summer or early fall where the wood is able to dry out, will not create an attractant for the Ips beetle. Another solution McKeever shared was creating very large piles so the second generation actually burrows deeper into the core of the pile instead of into the surrounding stand.
Douglas-fir Beetle
Douglas-fir beetle is another beetle that is not an aggressive tree-killer but will attack stressed trees that have root disease, or are weakened by fire, budworm or other drought. McKeever said they are seeing more Douglas-fir beetle but it is not because there are more beetles, it is because they are seeing a shift in the host. There are more stressed trees.
McKeever said they use MCH, an anti-aggregation pheromone. It comes in a bubble pack that is stapled to 30 trees per acre. It signals the beetles that there is no vacancy in the stand and they move on. McKeever said they recommend putting up the bubble packs by April 15. By April 22, 2016, they had nearly 1,000 Douglas-fir beetles appear in the Swan.
“That is only a week after we say to hang the MCH. The beetles are weather dependent. Once we get temperatures in excess of 65-70 degrees Fahrenheit that is when we see the beetles,” said McKeever.
McKeever said active forest management that maintains a healthy, vigorous stand, the trees are almost resistant. When the trees are not stressed and they are thinned enough to have access to water and nutrients, the trees will do well.
Black Pineleaf Scale
Black pineleaf scale is on the rise especially in the Missoula area. It is a native insect, infesting ponderosa pine needles. Its natural predators can be knocked back by pollution, dust and drought.
McKeever said DNRC has been getting a lot of service calls from people in the Westside of the Missoula, the Rattlesnake and in Frenchtown area with large, mature ponderosa pine that are much defoliated and have thinned crowns.
“When we are getting these densities, we are inhibiting photosynthesis because the needles are covered,” said McKeever.
Sprays can be effective. However McKeever again stressed managing for a healthy stand with resilient trees is the best solution to combat the black pineleaf scale as well.
Diseases & Other Killers
While beetles, budworm and pineleaf scale are highly conspicuous and cause noticeable damage to millions of acres of forests, others, including root and foliar diseases, progress much more gradually. They ultimately play a tremendous role in shaping forest composition.
Root disease fungi cause damage and mortality on nearly five million acres of forested lands in Montana, including three million acres of National Forest lands in western Montana.
White pine blister rust continues to damage and kill all western white pine, whitebark pine and limber pine (the five-needle pine species in the state) across most of their ranges.
For more information on these diseases visit http://dnrc.mt.gov/divisions/forestry/forestry-assistance/pest-management/Montana-forest-pest-condition-reports.
McKeever also discussed the damage road salt causes. She said that its affects are visible 30-50 feet out along salted roads. It is not species specific and affects all aged trees. Die-back and defoliation can be caused when the salt is sprayed or splashed directly on the trees. Chronic decline and mortality is caused when trees are growing in ditches that collect water or when salty snow is piled in and around trees.
When McKeever was asked what species are resistant to road salt, she said they all respond negatively to road salt. Pyramid Mountain Lumber’s Gordy Sanders said the solution to road salt damage is to use sand.
For more information contact the DNRC Forest Pest management program, 406-542-4330 or email McKeever at kmckeever@mt.gov.
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