NATURE NOTE – Number 45                         May 28, 2022                                                              

Introduction:

When we think of threats to the forest, the first one that usually comes to mind is fire.  In reality, fire comes in at about third place.  The biggest threat to the forest is something most people have never considered:

Our Current topic: Forest Insects

It is hard sometimes to separate fire, insects and diseases from each other when we start looking into the damage that they cause our forest.  Often, fire will open up opportunities for insects or diseases to enter a tree.  Other times, an insect will attack a perfectly healthy tree and allow a disease to enter the tree.  There is an almost an endless list of insect damage and disease that impact trees.  Some will affect only one species of tree, others and will go after a variety.  Much of the insect damage is minor, and will impact the tree for one season only.  It may stunt its growth or deform it some, but won’t necessarily kill the tree. Let’s start with a few of the more common insects in our area:

Gall-forming insects: These galls are easy to find, especially on oak trees, and look like brown, paper-like, golf ball sized spheres.  Most of these are caused by a wasp.  These are minor pests, but something scouts often find and inquire about.

Hemlock Wooly Adelgid:   Common on hemlocks, this is easily seen as a small white mass of foam on the underside of hemlock branches.  This is a serious disease and is causing significant loss of hemlocks, including those on our reservation.    

Tent caterpillars:  These very visible masses of webs at the base of branches are common in early summer on several species of hardwoods (frequently black cherry).  The “tent” covers the eggs and caterpillars as they feed on the host tree.  They seem to have a cyclical occurrence, with a year or two of heavy infestation followed by a smaller outbreak.  In spite of the impact on some branches, there is usually no long-term damage to the host tree.  If you catch it at the right time, you can often see caterpillars inside the “tent”.  Scouts love watching this squirming mass.

Bagworms:  Frequently on evergreens, especially red cedar, these brown slender bags are covered with what looks like short pine needles.  Inside are the larvae that will defoliate the host tree.

Gypsy moth:  A bad-actor you may have heard about.  The small white (females) and brown (males) moths cause huge hardwood defoliation in infected areas while in their colorful larvae stage (a pattern of red and blue dots on their prickly back).  This insect has spread south over several years as egg masses have been transported from infected areas on fire wood, logs, and vehicles.  This is major forest threat, but fortunately there is some cyclic pattern to this insect, and our area has seen only moderate infestations in the last few years.

Japanese Beetle:  Most folks know what this common insect looks like, but they may not know about its destructive appetite for many species of hardwood trees and shrubs as well as ornamental plants. Skeletonization is the feeding method of this guy.  It eats the green portion of the leave, leaving behind a web of non-eaten leaf.  As home gardeners know, this is a difficult species to control.

Southern Pine Beetle:  While there are a number of beetles that enter the wood and make tunnels in several tree species, perhaps the Southern Bark Beetle is the most destructive because of the damage it causes to pines being grown by the forestry industry for lumber. Some forest management techniques (such as thinning and early removal of infected trees) have been helpful in arresting the spread of this insect in pine growing areas.   

Bark Beetles:  A number of species (elm, hickory and other hardwood as well as southern pines) are invaded by these beetles that carve out galleries beneath the bark.  These can cause tree death, or degrade the value of lumber cut from infected logs.  Sometimes a fallen tree or log will readily reveal these twisted galleries underneath the bark.

Emerald Ash Borer: Aptly named, a ½” green insect that feeds on Ash trees by boring “D” shaped holes into the tree trunk. Spreading through the east, this insect is a major threat to ash trees.  Control is possible with insecticides on small numbers of trees such as a yard, but the survival of the ash species is in question pending an effective control being developed soon.

Longhorned Beetle:  This is new bad-guy in our area that has invaded from Asia and infecting many hardwoods, causing bark cracking, galleries, and exit holes leaking sap.  It has a distinctive look, starting with its 1-2” length, long white-banded antennae, and many white dots on a shiny black back. 

Spotted Lanternfly: Another Asian invasive species recently detected in northern Virginia, this may become a major problem for fruit trees and forests.  It also hitchhikes from one area to another in the form of egg masses on vehicles and pallets.  It’s a beautiful moth-like insect with black, white, tan, and sometimes-visible red in its wings.   Stay tuned for more info on this one.

In addition to the above, the forest is full of aphids, leaf miners, ambrosia beetles and many more insects.  A good field guide on insects will provide more information and perhaps open a whole new nature world to your scouts.

Opportunities: 

Our intent here is not to have scouts identify insects or to understand the details of the damage, but to make them aware of the impact insect have on forest health.  It takes very little effort to find the damage.  Just look at leaves.  Look at how they are damaged in different ways.  Look at logs and stumps for the galleries or tunnels.  Close examination of acorns, buds, flowers, and fruit will quickly reveal more insect damage.  Most scouts have never noticed this insect damage.  Help expose them to the many fascinating parts of nature.  Maybe there’s a future forest entomologist in your troop.  As always, thanks for looking at the NATURE NOTES.  Contact me at This email address is being protected from spambots. You need JavaScript enabled to view it. with any comments. 

Bob Garst