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Bark Beetles By Dawn Fluharty There are numerous species of Ips and Dendroctonus, commonly called bark beetles, which infest conifers throughout North America. Adults tunnel through the bark, mate, and lay eggs in the phloem (inner bark). The larvae develop in the phloem and cambial region. Pupal development is completed in the outer bark. Adults develop from pupae and emerge by boring out through the bark. Larval feeding interrupts the tree's ability to move water and nutrients within the host tree. Several species also introduce a fungus into the tree, which further inhibits the vascular system. Common species of Pine Bark Beetles include Mountain Pine Beetle, Western Pine Beetle, Southern Pine Beetle, Ips Engraver Beetles, and Spruce Beetles. What do they look like? Bark beetles themselves are typically small, 3 to 4mm long, with cylindrical bodies. Because they are so hard to spot on the trees, it's best to look for other signs of infestation, especially pitch tubes. Pitch tubes are "popcorn-shaped masses of resin" (USFS) that indicate a tree is trying to push the insects out. Other symptoms of infestation include reddish boring dust, adult exit holes, woodpecker damage, and yellowing foliage. The beetles commonly attack drought-stressed trees. High numbers of attacks to trees are possible, which can result in extensive vascular injury and, ultimately, tree death. Trees infested with bark beetles will gradually turn brown, defoliate, and die. Host material and range Because bark beetles are part of a large family of insects, the host tree range is wide. Generally speaking, bark beetles attack conifers. These beetles attack mainly pine trees, including the Loblolly, Lodgepole, Pinyon, Pitch, Ponderosa, Scotch, Shortleaf, Slash and Virginia varieties. These varieties of pine can be found all over the western and southern United States. Spruce trees can also be affected. Current threat Currently, Mountain Pine Beetle has reached epidemic levels in Colorado, reducing many of the native pine forests to standing dead- wood. The formerly lush green mountainsides of the Rockies are now reddish-brown or gray due to the devastation of this insect. Not only does Mountain Pine Beetle do its own damage by restricting water and nutrient flow within the host tree, but it can also act as a vector for Bluestain Fungus, a deadly infection. There are products on the market to treat for a beetle infestation, but there is no available treatment for Bluestain Fungus. While Mountain Pine Beetle does its damage in the Rockies of Colorado, Western Pine Beetle is most damaging in California, but its range extends northward into Oregon, Washington, Idaho, and www.arborage.com southern British Columbia; eastward into Montana, Nevada, Utah, Colorado, Arizona, New Mexico, and western Texas; and southward into northwestern Mexico (USFS). Meanwhile, Southern Pine Beetle has been found as far north as New Jersey and Pennsylvania, though it is found south to Florida and west to Texas. Isolated pockets have been found in New Mexico and Arizona. Treatment Research studies using TREE-äge Insecticide (containing 4% Emamectin Benzoate) have demonstrated great results against conifer bark beetles, depending on the pest species targeted. 1, 2 Injection tips • In resinous conifers, such as pine and spruce, start the injection immediately after drilling into the sapwood. A prolonged delay may reduce uptake on account of resin flow into opening. • Inject at the base of the tree. Inject into the stem within 12 inches of the soil, into the trunk or root flares. Make applications into intact, healthy sapwood. Do not inject into injured areas or areas with decay. Select injection sites associated with stem growth. • Work around the tree, spacing injection sites approximately every 4 inches of tree's circumference. • Drill through the bark then 5/8 inch to 1-5/8 inches into the sapwood with the appropriate-size drill bit. Use clean, sharp drill bits. Brad point bits are recommended. Precautions should be taken to avoid diseased areas and transferring infected tissues to other injection sites. Dawn Fluharty is the northwestern regional technical manager at Arborjet, with 11 years in the green industry. She holds a B.S. degree in Environmental Horticulture Sciences with a minor in Soil Sciences, and has her PCA (Pest Control Advisor) License in California. References 1 Effectiveness of Two Systemic Insecticides for Protecting Western Conifers from Mortality Due to Bark Beetle Attack. Don M. Grosman, Christopher J. Fettig, Carl L. Jorgensen, and A. Steven Munson. Western Journal of Applied Forestry 25(4) 2010 2 Efficacy of Systemic Insecticides for Protection of Loblolly Pine Against Southern Pine Beetles (Coleoptera: Cuculionidae: Scolytinae) and Wood Borers (Coleoptera: Cerambycidae). Donald M. Grosman and William W. Upton. Journal of Econ. Entomol. 99 (1): 94-101 (2006) Note: TREE-äge is a Restricted Use Pesticide and may only be sold to and used by a state certified applicator or by persons under their direct supervision. TREE-äge is not registered for use in all states. Please check with your state or local extension service prior to buying or using this product. TREE-äge is registered trademark of Arborjet, Inc. Arbor Age / July/August 2012 3 3 PEST OF THE MONTH