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NJDA Tests Bio-Weapon Against Hemlock Killer
For Immediate Release: June 2, 1998 Contact:

Hope Gruzlovic


NJDA's beneficial insect laboratory in Ewing, in cooperation with NJDEP's Division of Parks and Forestry and USDA's Forest Service (USFS) have released a natural predator of a devastating pest of hemlock trees in four locations around the state to test the predators' ability to control the pest.

Approximately 30,000 of the tiny natural predators, a black ladybug, have been raised in the Ewing laboratory and released to combat hemlock wooly adelgids, minute sap-sucking insects that can turn a healthy, 100- foot hemlock into a skeleton in just a few short years. The effectiveness and hardyness of the ladybug will be monitored over the next several years. Hemlock wooly adelgids are found throughout the state's 25,000 acres of hemlock forests. Without a natural predator, and with conventional treatment methods impossible in the mostly inaccessible areas where hemlocks grow, the pest, native to Japan and China, has spread from Massachusetts to North Carolina since the first adelgid landed in the United States in the 1920s. Since 1988, NJDA has been working with USFS and the state Bureau of Forestry on an impact study to determine the pest's effect on Garden State hemlock forests. In some of the study plots, hemlock mortality rose from under 10 percent to over 60 percent in less than four years. There has been no practical way to control the pest since the infested forested areas are usually inaccessible to spray equipment and aerial sprays cannot effectively reach the majority of the pests through the forest canopy. The voracious ladybug released last month was discovered in 1990 by Dr. Mark McClure of the Connecticut Agricultural Experiment Station while he was surveying for hemlock adelgid predators in Japan. His additional research indicated that the ladybug does reduce adelgid populations when released in hemlock forests.

Last year NJDA scientists acquired a small colony of the tiny predator ladybugs from McClure and began raising them in the laboratory. Once released, scientists expect the beetles will begin to feed on the wooly adelgids, reproduce and spread to neighboring trees through short flights or on strong breezes.