Control of Douglas fir beetles by woodborer beetles

Wildfires and bark beetles have interacted for centuries—and even millennia—to shape diverse and resilient forest ecosystems. However, the record-breaking wildfires of recent years in western North America have raised concerns that the vast areas of damaged and dead trees—essentially easily exploitable resources—might promote the growth of insect populations.

The Douglas-fir beetle, the primary mortality agent of Douglas-fir trees, often experiences population increases following wildfires. The same applies to many other phloem-feeding insects, such as various woodboring beetles, which are attracted to burned areas and colonize fire-injured trees.

In a recent study, Canadian researchers investigated the interactions between Douglas-fir beetles and woodboring beetles that exploit the phloem of fire-injured trees. More specifically, their hypothesis was that the rapid colonization of bark beetle niches by woodborers following wildfires might restrict Douglas-fir beetle population growth through interspecific competition beneath the bark.

The hypothesis was tested in three mature Douglas-fir forests in British Columbia that burned in 2017. The researchers found that both Douglas-fir beetles and woodborers preferentially colonized mature stands containing large-diameter trees with moderate fire damage.

When woodborers were absent, the Douglas-fir beetle’s reproductive rate was sufficient to cause a local population outbreak. In contrast, in stands where woodborers were abundant (more than 50% of trees infested), Douglas-fir beetles were unable to reproduce at outbreak levels.

These results indicate that competition from woodboring beetles can significantly limit Douglas-fir beetle outbreaks in fire-injured forests. From a forest management perspective, this suggests that forests should be managed in ways that support the success of economically harmless phloem-feeding insects—such as many woodboring beetle species—since their presence may help reduce the risk of bark beetle outbreaks following wildfires.

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A popular hobby risks ecological balance, private property and human health in Finland

Ticks carry bacteria and viruses with them. The bacteria are causing Lyme borreliosis, which is a serious disease but can be treated with antibiotics. In contrast, some viruses may cause Tick-borne encephalitis (TBE), which is a serious tick-borne disease in Europe that can only be avoided by vaccinations.

Today it was informed that the number of TBE cases has increased considerably in Sweden and Finland due to the climatic change and and COVID-19 pandemic, the latter of which has brought people for outdoor activities. At least in Finland one of the main causes was not mentioned. That is the dramatically increased number of white-tailed and also roe deer, both of which act as hosts to ticks, and therefore enable higher population sizes of disease causing agents.

Deer populations also cause major damage to young forests by eating hardwoods and pines, which result in direct losses to forest owners as well as directs forest owners to plant spruces, which in Central Europe have been attacked seriously by beetles, and the same has been predicted to happen also in Nordic countries if the climates continue warming as predicted.

Hunting is, however, a popular hobby in Finland, and people involved are bringing huge amounts of food to the deer in wintertime, which increases considerably their population sizes. That maximizes the amount of animals for hunting but also their effect on the spread of tick-borne diseases and forest damages. 

For anyone looking from the side, it should be imperative to end the feeding of deer due to the vast problems they cause. And the common sense says, that white tailed deer should be removed from the country due to its nature as an alien invasive species. It simply is not sustainable to jeopardize ecological balance with an aggressively reproducing alien animal, put the health of lay people at risk nor damage their properties because of a hobby - no matter how enjoyable that may be.

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