Pennsylvania Game News - May 2012 - 13

not build and then crash in natural cycles like the gypsy moth. The woolly adelgid has a complex life cycle. At first, the insects are all female. They develop asexually and have six phases of development: egg, four instar nymphal stages and adult. An instar nymph is one that is between molts. The woolly adelgid produces two overlapping generations per year, which allows the population to quickly rebuild. Some scientists consider the woolly adelgid to be the greatest threat to our forests and they’re anxious to find ways to control it. The biggest hope seems to lie in a biological control. There are native species of insects that prey on the woolly adelgid, but none has had a significant impact on adelgid numbers. As a result, scientists are looking at importing natural adelgid enemies from China and Japan. Of five adelgid predatory beetles studied in Japan, a lady bug beetle shows the most promise because it feeds on both the larvae and adults. Three lady bug beetles, all in the genus Scymnus, have been imported from China as well. All three favor adelgids over other prey, and all prefer to feed on adelgid eggs, but they will also eat the insect in other stages of its development. Leaving the comfort and coolness of the hemlock grove I head back to my truck. Following a cow path along the creek I noticed the straight trunks of several large ash trees. In antiquity, the chariots of ancient Egyptian pharaohs were made of ash; today ash is used to make baseball bats, snowshoes, hockey sticks, pool cues, and tool handles, yet even this sturdy tree is threatened by an invasive Asian beetle with the potential to wipe out all the ash trees in the entire country. First identified in 2002, in Michigan, the first emerald ash borer (EAB) infestation in Pennsylvania was detected in Butler County in 2007. In 2008, infestations were confirmed in Mercer and Beaver counties, and a year later, in Mifflin, Lawrence and Westmoreland counties. Currently the
MAY 2012

entire state is under a quarantine, to limit the spread of this pest. The emerald ash borer beetle can kill a healthy tree in three years or less. Since 2002 the EAB has killed tens of millions of ash trees across the country. Scientists think the EAB was introduced into this country on infested shipping pallets. The EAB is not considered a pest in its native Asia, because native natural enemies control its population and host trees there have evolved a resistance to the insect. In this country, some wasps and certain birds, notably woodpeckers, will prey on the insect, but not enough to keep it under control. As a result, an ash tree once infected by the beetle is doomed. The emerald ash borer is only a half-inch long, metallic green, and lays its eggs on the bark of ash trees. When the eggs hatch, the larva bore through the bark, creating tunnels. Soon, these tunnels cut off the tree’s nutrients and water, effectively killing it. The EAB is considered a good flier, but people inadvertently moving EAB infested firewood, where larvae can live up to two years under the bark, are thought to be the primary reason for its spread. The threat of the EAB is great, as the loss of millions of ash trees will have serious environmental and economic impacts. Scientists are working to find a biological control to combat this insect. Last spring, small non-native wasps were released into three state forests, North Park and Deer Park in Allegheny County, and on SGL 252, in Union County. It’s hoped these parasitic wasps slow the spread of the EAB, but it’s unlikely the insect will be totally eliminated. Meanwhile, people must do their part by using only firewood taken within 50 miles of where it was cut and not any from out of state. Nearing my truck I passed several
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Pennsylvania Game News - May 2012

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