Threats to our forests

Many area residents and visitors have observed threesided purple boxes hanging from trees along many of our roadways.

They certainly look out of place among our vibrant green-forested summer landscape. However, they serve an important purpose. They contain sticky traps for attracting adult emerald ash borer beetles. It's part of a statewide survey to assess the spread of this invasive insect pest.

This wood-boring beetle is native to China and eastern Asia. Adults are dark green, one-half inch long and oneeighth inch wide. They fly only from early May until September. The larvae spend the rest of the year underneath the bark of ash trees.

When they emerge as adults, they leave D-shaped holes about one-eighth inch wide in the bark of their host trees.

The State Agriculture Department has placed these purple traps in 35 counties. Remaining counties will be surveyed by other cooperating agencies, such as the Forestry Bureau.

Last summer, emerald ash borer beetles were detected in Butler and Allegheny counties. Quarantine has been imposed for these counties and neighboring Beaver and Lawrence counties to restrict the movement of ash nursery trees, green lumber, ash tree parts, all hardwood firewood, and all woodchips.

Those in the quarantine area to use only locally harvested firewood, burn all firewood on-site, and not carry it to new locations.

Emerald ash borer is a huge threat. If not stopped, it will forever change the composition of our forests, eliminating one of our most common tree elements.

Unfortunately, it's not the only exotic insect pest threatening forests in northcentral Pennsylvania.

After causing severe defoliation in the 1990s, gypsy moth populations crashed during the start of this decade. However, their populations are now rebounding.

Hemlock wooly adelgid, native to Asia, is just beginning to enter our region from the south. It poses the very real threat of erasing our state tree, the eastern hemlock. If that comes to pass, we will have lost what is perhaps the most important tree component in our forests.

Viburnum leaf beetle, an import from Europe, has entered our region in recent years. Hobblebush, high bush cranberry, maple leaf viburnum, arrowwood, nannyberry, and wild raisin all are beautiful spring bloomers and important berry producers in our region. Unfortunately, in the upcoming years many of these native shrubs will succumb to viburnum leaf beetle.

Willow leaf beetle is another exotic pest that causes severe defoliation of our native willows, giving the trees a dead appearance after being completely defoliated by both the larvae and adults. The good news is that willows are resilient and seem to be able to bounce back from these annual defoliations. Unfortunately, with no leaves during the heat of the summer, willows defoliated by the willow leaf beetle offer no shade to our coldwater streams and the trout that inhabit them.

Exotic sirex wood wasps are recent arrivals. These wasps attack and kill red and white pines, along with other pine species. Recently, they have been detected in Tioga County.

With each new attack by an alien invader, our forest ecosystems lose biodiversity and become less resilient. With each loss, our forests are less able to function like they were designed and to support the wildlife that relies on these native tree species.

Everything in nature, including humans, is connected. When we lose one element of a natural system, all of the other parts will feel the impact.