1Entomology 462Ornamentals Pests: BorersDavid J. Shetlar, Ph.D.The “BugDoc”The Ohio State University,OARDC & OSU ExtensionColumbus, OH© October, 2004, D.J. Shetlar, all rights reservedWoody Ornamental Pest GroupsBorer Symptoms“SUDDEN” Plant DeathSawdust from HoleSap/Pitch from Hole“Gouty Growth” on Trunk or Branch2Sudden death to spruce terminal caused by white pine weevil larvae.Bronze birch borer larvae usually cause host trees to die from the top down.Sawdust like frass produced by rhododendron borer. Dry sawdust being produced by a borer suggests that it is feeding in a dead area.Pitch mass caused by zimmerman pine moth larva. Sap or pitch flow suggests that the borer is feeding in living tissues.3Woody Ornamental Pest GroupsChewing Pests - BorersBeetles that are Borers -Roundheaded Borers (longhorn beetles)Flatheaded Borers (metallic wood borers)Bark Beetles (bark, shothole, ambrosia beetles)Weevils (shoot & root weevils)Moths that are Borers -Clearwing MothsCarpenterworms (leopard moths) Twig, Tip & Shoot MothsRoundheaded Borers (Cerambycidae)(adults are known as longhorn beetles)Elm borer adult, note antennae that are, at least, as long as body.Elm borer larva is oval in profile and produces an oval hole.Elm borer pupa.4Most roundheaded borers attack trees or shrubs that are dying or have recently died. In many cases, the plant may not overtly exhibit signs of death, at least to inexperienced plant care managers.The few roundheaded borers that attack stressed trees usually feed in the heartwood rather than the cambium area. This may weaken thestructure of the tree, but does not kill it outright since girdling does not occur in the sapwood area.Unfortunately, the larvae of cerambycid larvae are commonly found under the bark of dead trees and are accused as being the cause of the plant death.Roundheaded borers usually make round or rounded-oval emergence holes.One roundheaded borer, the twig girdler has adults that cut a groove in small branches which cause these to eventually break and drop. Their larvae feed within the girdled branch. The oak pruner has larvae that girdle small oak branches that cause these to also break out of the trees. The larvae also feed in the dead branch. Both pests rarely warrant control.Locust borer adult on goldenrod, its favorite fall feeding ground.Locust borer emergence hole. Most longhorn beetles produce round or rounded-oval holes.5Pine sawyer adult and emergence hole. Pine sawyers normally don’t kill pine trees, but adults transmit pine wilt nematodes that do!Pine sawyer larvae, lower left.Spotted pine sawyer adult.Oak Twig PrunerAdultLarva in twig.Sawdust-like frass being pushed out of pruned branch by larva.6Flatheaded Borers (Buprestidae)(adults are known as metallic wood boring beetles)Flatheaded appletree borer larva.Flatheaded appletree borer adult emerging.Adult flatheaded appletree borer.Flatheaded borers are called this because the first thoracic segments BEHIND the head are often expanded laterally and flattened. These larvae usually feed in the cambium or sapwood of host plants and they produce very flat and straight-sided burrows. By feeding in the sapwood, these borers commonly girdle their hosts, causing sudden death.The adults are called metallic wood borers because they are often coppery or bronze in color. Some are bright iridescent green or blue and are highly prized by beetle collectors. When the adults emerge, they usually produce flattened oval or D-shaped holes.The genus Agrilis has many species which are commonly encountered in landscape trees. The larvae of this genus are very thin and narrow with the thorax only slightly expanded laterally. Most adults in this genus leave characteristic D-shaped exit holes.7Bronze birch borer larva in sapwood. Bronze birch borer adult emerging.Honeylocust borer adult. Honeylocust borer emergence hole.Note characteristic D-shape.Bronze birch borer females tend to lay their eggs in bark fissures or under flaps of bark. Therefore, if a preventive insecticide is used, thorough coverage is essential for success.8Bark Beetles (Scolytidae)(also called engraver or ambrosia beetles)Cedar bark beetle adult. Cedar bark beetle larvae.Pine Ips beetle and emergence hole. These beetles are sometimes called shothole beetles.Bark beetles usually attack stressed or dying trees. As with longhorn borers, these beetles are often blamed for the death of their host tree.The European elm bark beetle transmits Dutch Elm Disease which is a fungus that the adult beetles pick up when they exit infected trees. These beetles feed on the branches of healthy elms and accidentally introduce the fungal spores. The fungus rapidly attacks the new trees, causing branch or whole tree dieback in a year or less. These dead or dying trees serve as new hosts for the beetles, thereby perpetuating the cycle of the beetles and fungus.Some conifer bark beetles, especially the southern and western pine bark beetles, perform “mass attacks” where an adult may find a weak or apparently healthy tree. Once located, this “scout” releases an aggregation pheromone that attracts hundreds of additional beetles. All the beetles bore into the tree at once, overwhelming it.In landscapes, recently transplanted larger trees and trees suffering from root damage due to construction or disease are especially prone to bark beetle attack.9Weevil Borers (Curculionidae)White pine weevil adult female laying eggs.White pine weevil larvae burrowing down leader.Leader killed by white pine weevils.Clearwing Borers (Sesiidae)This group is commonly listed as the AegeriidaeLesser peachtreeborer adult.Ash/lilac borer larva in lilac branch.Maple callus borer adult.Peachtree borer larva in sand plum.10The clearwing moth borers are some of the most common key pests found in urban landscapes. While they usually can not attack healthy plants, once they get established, they may reinfest the same plant year-after-year until it is girdled and killed.Some of the most important species are the dogwood borer, the rhododendron borer, the peachtree borer (in flowering peach, plum and cherry), the ash/lilac borer, the banded ash clearwing, and the oak borer.Most of the clearwing borer adults can be monitored by using pheromone traps. Traps are placed out two weeks before the species normally flies. When the first moth is captured (males fly first), there is usually 10 to 14 days before females are developed sufficiently