The good, bad and hopeful about invasive insects

CORNWALL — Growing populations of invasive insects and the harm they pose to local forests drew a crowd to a Zoom talk co-sponsored by four local organizations on Saturday, March 5. This talk was the first in what will be a series of talks and events in the coming months.

“Impact of Invasive Insects in Connecticut Forests,”  drew 67 online participants — and lots of questions afterward.

Rob Clark, a research scientist affiliated with the Great Hollow Nature Preserve and Ecological Research Center in New Fairfield, Conn., presented the program sponsored by the Cornwall Conservation Commission, Cornwall Conservation Trust, Cornwall Association and the Cornwall Library.

Clark’s topics included how to identify and discourage the toehold on local forests and back yards from such pests as the hemlock-loving woolly adelgid; the gypsy moth that hit plague levels last year (and which has undergone a name change); the devastating emerald ash borer; the spotted lanternfly; and further afield to the presence of tree diseases, no less lethal.

But most are good

But there are also the good insects that promote healthy forests. A virtual early spring walk along a nature trail in a local forest proved the point for viewers. The majority of a forest’s insects are beneficial to the forest’s ecosystem, Clark explained.

For example, wildflowers produce seeds and some of those seeds offer a sweet coating that is attractive to a particular type of black ant, the scavenger aphaenogaster, abundant in numbers in most forests and arguably the most common insect in the U.S.  For short, they are called the common forest ant, highly beneficial and of good reputation. They don’t eat plants; they scavenge among the forest’s leaf litter layer. These are not the black ants that enter homes and self-invite to picnics.

The one thing that they do really well is to pick up those wildflower seeds and deposit them in a spot where they will grow well and produce new plants to adorn the forest.

“We don’t notice them because they are just doing the work,” Clark said.

Yet some are devastating

The dastardly invasive insects are found at the other end of the popularity spectrum, although the designation of an insect as good or bad, is a human measurement, Clark said.

The most destructive insect in the state at present is the tree-killing Emerald Ash Borer.

“They are a problem,” he said of the ash borer. “This insect is here and doing damage, and it has been here for years with no natural enemies.”

Latent insect pests go through cycles, but do no real damage, Clark said. For example, the lesser maple spanworm will create pinholes in some maple leaves without causing lasting harm.

Birds and other natural predators provide reasonable control of the insect populations. Healthy forests and healthy plants also discourage pests.

The hemlock woolly adelgid has been destroying hemlocks for more than 70 years. Clark noted that some years are good, with little damage; in other years the damage is significant.

Cold winters can help

Mild winters bring on a significant outbreak, he explained, but a cool, shady ravine can offer protection.

Climate change is a factor. Tree health is boosted by a cold winter.

The insect formerly known as the gypsy moth, dating back to 1900, has a new name: spongy moth. They first got the new designation in Quebec and in France; the name has now been adopted in the U.S. The word “spongy” describes their egg masses deposited on tree bark and wood. They are wholly different from tent caterpillars.

Spongy moths are especially drawn to oak trees. An oak tree can survive an infestation for two consecutive years. Any longer, the tree probaby will not make it.

Expect to see the spotted lanternfly, coming this way from China as it pursues its favorite Tree of Heaven, used widely as an ornamental. It is also partial to vineyards and is now attracted to walnut and sycamore trees.

Some good news: the Asian longhorn beetle is being controlled successfully by quarantine.

After a stint at Washington State University, Clark has returned home to his native Connecticut to pursue entomology research with a home base at Great Hollow Preserve. He now works as an independent scientist for nonprofit organizations and private groups, also encouraging citizen science along the way.

A “tree health hike” at a Cornwall Conservation Trust property is being planned between April and June; Clark will lead the live tour. To view the video from Saturday’s talk, go to www.cornwalllibrary.org.