From the Directors Desk: The Latest on New York State's Top Six Insect Threats

By Fred Breglia

With winter’s cold wind and plummeting temperatures, some days are best spent sitting inside learning the latest about New York State’s invasive insects.

The top six threats are the Asian Longhorned Beetle, Emerald Ash Borer, Gypsy Moth, Hemlock Woolly Adelgid, Sirex Woodwasp, and Viburnum Leaf Beetle. Though the Viburnum Leaf Beetle and Gypsy Moth are found at Landis, thankfully none of the other invasives have been discovered. That being said, several have been found in neighboring counties and we are monitoring the collections, gardens, and grounds for signs of infestation.

  • The Emerald Ash Borer (EAB), Agrilus planipennis, was first discovered in southeastern Michigan in 2002 and in NY in 2009. This beetle infests and kills ash trees including green, white, black and blue ash. The larvae tunnels under the bark, disrupting the flow of nutrients and water, and effectively girdles the tree. A large area in Albany County has been quarantined, with most infestations located in the town of Bethlehem. Detection has also occurred in Livingstonville, south of Middleburgh, and in Syracuse. The NYS Department of Environment Conservation hung monitoring traps at Landis, but fortunately no EABs have yet been caught. During the winter, the EAB hibernates in pupae form. Research suggests temperatures below freezing kill some of these insects before hatching. The releasing of a stingless wasp, EAB’s main predator in Asia, is a control technique being tested as it kills both eggs and larvae. The goal is to establish wasp populations that can eventually bring EAB population numbers down to a sustainable level.
  • Another invasive is the Sirex Woodwasp, Sirex noctilio, a native to Eurasia that has caused major damage in the Southern Hemisphere, including Australia and South Africa. As the female lays an egg under the bark, she secrets a toxic mucus and symbiotic fungus. The mucus creates a suitable environment for the fungus, which in turn decays the wood, making it easier for the larva to digest. The larvae then tunnel deep into the trunks, weakening and sometimes killing the trees. First discovered in the US in Otsego County in 2004, the greatest damage is seen in plantations of Scotch, Austrian, and red pine. A parasitic nematode, Deladenus siricidicola, which infects the woodwasp larvae and ultimately sterilizes the adult females, has been used for control. Other predators include birds such as the swallowtail and black spotted woodpecker.
  • The Hemlock Woolly Adelgid, Adelges tsugae, was first discovered in the Hudson Valley in the 1980's and has since spread throughout the State. It is related to aphids and is native to parts of Asia. This pest uses its long mouth parts to extract sap and nutrients from hemlock foliage, causing needles to discolor from deep green to grayish green and drop prematurely. The loss of new shoots and needles impairs tree health and is usually fatal after several years. Valued plantings of the Eastern hemlock could be ravaged by the adelgid, and the natural stands of hemlock in forests and parks would be greatly affected. This is especially true at Landis where many acres of hemlock thrive, including about 20 acres of old growth hemlock. New attempts to control the pest involve the release of beneficial beetles native to the Pacific Northwest that eat nothing but adelgids. Systemic insectides have also proven to be somewhat effective.
  • The Asian Longhorned Beetle (ALB), Anoplophora glabripennis, is a species native to eastern China, Japan, and Korea. It was discovered in southern NY in 1996. No new infestations have been detected since 2007, and all have been in New York City and Long Island. Most of these infestations were eradicated in 2013, though populations still remain in Queens, Brooklyn, and Amityville. The ALB prefers maples including red, silver, and sugar maples. It does most damage in the fall during its larvae stage. The larvae chew tunnels through the wood to the tree’s heart, where they overwinter as pupae. Early detection and burning trees on site have been the best controls of this insect, which is able to fly one mile in search of a new food source.
  • The Viburnum Leaf Beetle (VLB), Pyrrhalta viburni (Paykull), is a non-native that first appeared in NY along Lake Ontario in 1996 and has steadily spread. Detections have been made in almost every county including Schoharie. It is a voracious eater that can defoliate viburnum shrubs entirely. The insect overwinters in its egg stage, then hatches out in spring and feeds on the newly formed leaves, stressing the plant. After the crawlers leave, the adult beetle comes back to consume whatever remains. Plants may die after two or three years. Luckily, several generalist predators feed on VLB larvae including lady beetle adults and larvae, lacewing larvae, and spined soldier bug nymphs and adults.
  • The Gypsy Moth, Lymantria dispar dispar, introduced in Maine in 1869, has spread throughout the Northeast. Egg masses are found on tree branches and trunks. In the spring, the larvae disperse by hanging from silk threads that are carried by the wind. The larvae prefer eating oak leaves, but will feed on over 300 species of trees and shrubs, creating massive defoliation. Since females will lay eggs on dead wood, firewood is commonly a means of transport, so there is a regulation in NY that limits the transportation of untreated firewood to less than 50 miles from its source. Predation by some beetles and the white-footed mouse is an important factor in population control, as well as heavy rainfall during the larval stage.

If you believe you have spotted any of these invasives, it is best to contact the NYS DEC at for more assistance. You can also contact me for more insight on any of these pests.

Winter 2016

Volume 34 , Number 1

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