Pat Sziber

Above images courtesy US Forest Service

This is not a good time to be a tree, at least not for some of our native tree species. Already stressed by erratic weather events such as periodic drought and scorching summer temperatures, they suffer increasing attack by pests, many of which are alien invaders posing a serious threat to their survival.

The Asian longhorned beetle, which arrived in packing material from China, has been in New Jersey since 2002. It is primarily a threat to maple trees but is also found in other species. Once thought to be under control, it is making a comeback. The emerald ash borer has not yet appeared in our state but it is in bordering states and foresters are on the lookout for it here. The native southern pine beetle, which is about the size of a grain of rice, is causing widespread damage in our Pinelands. It thrives in dense pitch pine stands and is spreading fast. It causes the needles to yellow and turn brown and eventually kills the tree. The State Forest Service is working to control it by cutting buffer strips around infected areas and periodically thinning dense stands.

The gypsy moth, introduced from Europe in 1869, prefers oak trees. Our heaviest infestation occurred in 1981 when 800,000 acres of New Jersey forest were lost. The population was low this year, probably due to vigilance, natural cycles and biological control. Hemlock woolly adelgid, which arrived from Asia in the 1920s, attacks hemlock trees and possibly spruce. The last "bug thug" on our list is not an insect but is probably spread by bugs that, in and of themselves, are mostly benign.

Bacterial leaf scorch, which is caused by Xylella fastidiosa, is causing widespread loss of oak trees by clogging the xylem, the trees' water and nutrient transport system, "scorching" the leaves and killing the trees over time. All of these infestations eventually kill their tree victims.

There are some excellent resources where you can learn how to identify the thugs and take action. An interactive exhibit at the New Jersey Forest Resource Education Center, a joint project of the US Department of Agriculture and NJDEP, provides identification tools, illustrates the signs of infestation and educates visitors on the steps they should take. The Center, which features many other programs and exhibits on forestry and forest stewardship, is located in Jackson Township off Exit 21 from Route I-195.

Directions can be found at Two very informative on-line resources are worth checking out.

To learn more about the pests threatening New Jersey's trees, go to

And there's a wealth of practical information for firewood users at

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Last revision: Wednesday, August 30, 2011