When was the most recent time you took a walk in your woods or a nearby forest or hiked along some of the logging roads in our area, state game lands, or state forests? If it was in the last few months, did you notice anything a bit unusual in the crowns or tops of the trees? Specifically, was there anything unusual looking about the leaves?
Trees, just like humans, can be affected by various factors called stressors or disturbances. In the case of trees, these can include attacks by insects, drought, floods, windstorms, and fire. Recently, some of our area forests have been under extreme stress by an invasion of spongy moths. Added to that, several weeks of no rain have occurred, and with no rain in the near future forecast, there is a real concern for drought conditions.
When trees are subjected to a disturbance (such as drought or insects chewing on their leaves), their capability to soak up carbon dioxide and therefore grow is greatly reduced. Further, these stressors will weaken a tree and make it more susceptible to pest organisms or disease. If a drought continues long enough, both deciduous trees and conifers will shed leaves or needles, reducing their ability to photosynthesize.
Unfortunately, throughout our region, there has been a continued activity of spongy moths and now, a prolonged period of no rain. The spongy moth caterpillars stripped the trees of their leaves, then transformed into the pupa stage, later hatched into male and female moths that would breed and allow the females to lay egg masses on the trees’ trunks and limbs. Once the leaves had been completely eaten by the caterpillars, the tree would expend its energy in an attempt to grow a replacement set of leaves. If this occurs, there is a real chance that the tree will not have enough energy to produce acorns in the same season.
If a period of no rain continues long enough to produce drought conditions, the lack of needed moisture may also stress the tree and may also contribute to a reduced or total lack of acorn production for the season.
A month or so ago, if you hiked in the woods throughout some of Lycoming County, you might have been witness to a very stressful activity in the overhead canopy of the trees. Not in all areas, but in all too many of our privately owned as well as state-owned forests, spongy moth egg masses were beginning to come alive!
These minute, ¼-inch-long caterpillars were emerging by the thousands and would be carried by the wind to spread throughout the nearby trees. Then, they would work their way to the tops of the trees and to the end of the limbs and spend the next few weeks munching away until, in many cases, there was not a single leaf remaining on the tree. The springtime forests had an eerie appearance of winter conditions, with no visible leaves to be seen.
The spongy moth invasion was prevalent last year and again this spring. That resulted in two seasons of back-to-back heavy defoliation. And now, we seem to be in a continued drought condition in much of our area. Trees can withstand a stressor event from time to time and recover to continue growing and producing nuts or fruit in seasons to come. But, multiple disturbances will weaken a tree, and too many of these events will combine to eventually kill the tree.
Should we be concerned? Yes, very much so. In the least, those trees that were subjected to the spongy moth caterpillar attack will not produce fruit or nuts this year. That means no acorns, which deer, bears, and other wildlife count heavily upon to develop a thick enough layer of fat to carry them through the winter months. In the worst-case scenario, too many of these stressor occurrences will kill the trees, potentially leaving vast forest areas devoid of the acorns and other nuts and fruit that wildlife depends upon as their main food source.
There is no effective way we can counter any drought conditions. As to the invasive spongy moths, there is only one way to effectively address the situation, and that is to do an aerial spraying of pesticides. It has to be done during a short window of opportunity in the spring, just after the caterpillars begin to appear from the egg masses and before they are too large to be affected by the pesticide.
This past spring, there were vast areas that were not subjected to the defoliation by spongy moth caterpillars. But unfortunately, there were also large tracts of forests that were completely defoliated. If you had trees that were stressed by the spongy moth caterpillars this spring, I hope you will seriously consider aerial spraying next year. Not doing so just may result in the complete loss of your acorn and nut and fruit-producing trees!
