<span style="font-weight: bold"> <span style="font-size: 17pt"> Get ready for a gypsy moth invasion</span> </span>
Widespread egg masses in winter foreshadow bumper crop of pests
January 27, 2013
The medical world can often predict the next outbreak of the flu. By the astronomical amount of people suffering from this winter's influenza epidemic, the Centers for Disease Control and Prevention's sniffling forecast got it right.
There's some predicting going on about a possible outbreak within the woodland community. Regionally speaking, there's some chatter about a creature waiting to emerge this spring — perhaps millions of them. These creepy, crawly critters won't attack our sinus passages and make us feel miserable like the flu, but will focus on the sinus lobes of tasty oak leaves and other hardwoods and make them disappear.
<span style="font-weight: bold">Yes, folks, are we ready for another bout of gypsy moths?</span>
First, let's learn a little about these nasty insects. According to the Penn State College of Agricultural Sciences, "The gypsy moth, Lymantria dispar, was accidentally introduced into Massachusetts in l869. By 1902, this pest was widespread in the New England states, eastern New York and regions of New Jersey. The gypsy moth was first detected in Luzerne and Lackawanna counties in northeastern Pennsylvania in l932. Pennsylvania's infestation progressed south and westward, following the mountain ridges. During the late 1970s and early l980s the leading edge of the infestation advanced into Centre, Blair, Huntingdon and Clearfield counties. Heavy defoliation and subsequent tree mortality has occurred along mountain ridges in forests comprised primarily of oak. It is the most important insect pest of forest and shade trees in the eastern United States."
Gypsy moth caterpillars consume the leaves of deciduous tree species, most preferably oak and maples. During heavy infestations, I have seen them devour the leaves of practically every type of tree. This is one of the reasons why several Pocono communities with large tracts of forested land are concerned about another outbreak of gypsy moth caterpillars, such as what we experienced a few years ago.
The last outbreak occurred during a four-year period, 2006 to 2009. The devastation of Pocono forests was evident: tall, standing dead trees, mostly oak species. Many trees can withstand a season of defoliation from gypsy moths, but consecutive years of stressful infestation usually kills the tree.
No one wants to see that happen again, but can we see into the future Forecast for gypsy moths
One of the telltale signs of worse things to come is the amount of gypsy moth egg masses laid on the trunks of trees. A good way to analyze the intensity of gypsy moth caterpillars' destruction in your forest is to conduct an egg mass count per acre. The eggs masses are light tan, about 1.5 inches in length and may contain 400 to 600 eggs.
<span style="font-weight: bold">So, how many egg masses should cause concern?</span>
Tim Marasco, field operation supervisor of the Forest Pest Management Division of the Pennsylvania Bureau of Forestry, explained: "We have learned that a density of at least 250 egg masses per acre is reason to be concerned for residential communities. Noticeable hardwood leaf defoliation and nuisance conditions are usually expected. Furthermore, when egg mass densities reach 500 per acre, the result may be problematic, and proactive measures are recommended, such as aerial spraying."
How many gypsy moth egg masses are in forested areas throughout northeastern Pennsylvania? Most likely an impossible question to answer, but is there really a concern of another gypsy moth outbreak?
I asked John Maza, Wayne and Lackawanna counties district service forester for the Pennsylvania Bureau of Forestry:
"Our trained forest technicians conducted gypsy moth egg mass counts on state forest lands throughout the northeast and found relatively low numbers of egg masses per acre," said Maza. "However, there could be outbreaks in isolated pockets of forests."
Marasco and Maza report that the highest densities of gypsy moth egg masses deposited this past fall are in public lands in central and northwestern Pennsylvania. The Bureau of Forestry anticipates aerial-spraying nearly 43,000 acres to combat gypsy moth caterpillars.
<span style="font-weight: bold">Caterpillar control</span>
That's a lot of acres to treat with pesticides. What is being sprayed, when is the best time to spray, and are there environmentally safer alternatives?
Marasco explained, "The Bureau of Forestry uses an insecticide called Bacillus thuringiensis var. kurstaki, otherwise known as BTK, a biological insecticide. Typically used as an aerial application, BTK must be sprayed when young caterpillars are in the feeding stage. It is ineffective on egg masses and non-feeding adults."
Literature provided by Penn State College of Agricultural Sciences lists a number of natural controls, safe non-chemical biological control methods and topical insecticides. Several natural controls include native predators and parasitoids — flies and wasps that attack gypsy moths and caterpillars. Extreme cold weather, when air temperatures reach -20 degrees F or colder during the winter, will kill exposed egg masses.
There is a naturally occurring virus called the "wilt," which can result in massive mortality of caterpillars. Although the virus is always present, it seldom affects the larval stage until they are under stress from overcrowding or reduced food availability.
Another natural control: The fungal insect pathogen, Entomophaga maimaiga, is found during wet spring weather, which causes collapse of heavy infestations of this pest in many areas of Pennsylvania.
Non-chemical controls include wrapping burlap around tree trunks to capture gypsy moth caterpillars as they return back up on tree trunks to their evening retreat. Another alternative: placing traps baited with a synthetic pheromone that attracts males.
Knowledge is a powerful weapon, so use as many weapons as possible to learn more about gypsy moths. Resources include your county Conservation District Office, the state Bureau of Forestry or Penn State College of Agricultural Sciences. These agencies can also provide a list of professional services and consultants which might help and guide you in reaching your forest management objectives.
However, as Marasco informed me, "By counting the amount of gypsy moth egg masses during the fall and winter months, we can predict the possibility of gypsy moth outbreaks. If you discover gypsy moth caterpillars in your forest, it's too late. The time is now to find the problem before it happens