Tree Care Advice – Insects Kill

Bugs in the Trees? Get the Fly Swatter!


  • Exotic insect species can pose serious problems to many tree species in the United States. Invasive insects usually enter the country undetected and uninvited.
  • In these new environments, there are few or no predators, parasites, or diseases to keep the populations of an invader in check.
  • Our natural and urban tree systems are constantly threatened by the establishment of exotic, invasive plant pests.
  • Early detection reduces overall cost to industry by either preventing pest establishment or allowing arboriculture researchers to conduct appropriate studies for management recommendations.

You can help defend the country from these invasive pests. Be an Invasive Insect First Detector!

Who is a First Detector?

A First Detector is anyone who notices an unusual outbreak, an insect pest of concern, or symptoms of an insect pest of concern. Arborists are First Detectors. Qualified Tree Workers are First Detectors. Homeowners are First Detectors.

Look for any of these four insects. Contact Midhurst Tree Care for instructions on how to report and eliminate them. Read more about how to identify insects, see the symptoms of an infestation and how to control or eliminate the problem.

Asian longhorned beetle – Anoplophora glabripennis

  • Adult beetles are .75 to 1.25 inches long, with jet black body and mottled white spots on the back.
  • The long antennae are 1.5 to 2.5 times the body length with distinctive black and white bands on each segment.
  • The feet have a bluish tinge.
  • The Asian Longhorn Beetle has one generation of offspring per year.
  • Adult beetles are usually present from July to October, but can be found later in the fall if temperatures are warm.
  • Adults usually stay on the trees from which they emerged or they may disperse short distances to a new host to feed and reproduce.
  • Each female is capable of laying up to 160 eggs. The eggs hatch in 10-15 days and the larvae tunnel under the bark and into the heartwood of the tree throughout the winter, severely undermining the strength of the tree and its limbs
  • The adults emerge from pupation sites by boring a tunnel in the wood and creating a round exit hole in the tree.
  • Adult beetles then feed on the bark and leaves of trees.
  • Asian Longhorn Beetles kill trees!


  • Host material living, dead, cut or fallen.
  • Maple species including boxelder, Norway, red, silver, and sugar maples.
  • Alders, birches, elms, horsechestnut, poplars, and willows ash, mulberry, and black locust.
  • Chinaberry, mulberry
  • All hardwoods except oak, All young trees – even shrubs, but NOT conifers (evergreens).

Signs and Symptoms:

  • Large (0.75 – 1.50 inches long) with very long black and white banded antennae.
  • Coal black with irregular white spots on its back.
  • Adult emergence occurs between June and October with peak populations occurring in early July.
  • Infested trees are identified by the presence of the beetle.
  • Holes bored for exiting or egg laying.
  • Sawdust at the base of the trees or on their branches.
  • Sap that sometimes drips from the trees.


  • Remove infested trees and destroy them by chipping or burning. Call a professional tree company.
  • To prevent further spread of the insect, quarantines are established to avoid transporting infested trees and branches from the area. Destroy infested trees along with the eggs and larvae within them.
  • Grind the stump to a depth of 8 inches.
  • Pesticides are not an effective control measure because they cannot reach the eggs, larvae and maturing beetles dwelling deep within the trees.
  • Holes bored for exiting or egg laying.
  • Trained Bucket Truck operators and Tree Climbers are effective when leaves are on the trees.
  • Imidacloprid, a chemical with systemic properties and low mammalian toxicity, has been found to be effective against adult ALB as it feeds on small twigs, the female when depositing eggs, and young larvae.

Emerald Ash Borer – Agrilus planipennis

  • Emerald ash borer is an exotic beetle from Asia, and was discovered in July 2002 feeding on ash (Fraxinus spp.) trees in southeastern Michigan.
  • Larvae feed in the cambium between the bark and wood, producing galleries that eventually girdle and kill branches and entire trees.
  • Evidence suggests that Agrilus planipennis has been established in Michigan for at least six to ten years.
  • This exotic pest is also established in Illinois, Ohio, Pennsylvania, and Ontario, Canada. In 2003, infested ash nursery trees were also found in Maryland and Virginia.


  • Adult beetles are generally large and a bright green.
  • The emerald ash borer generally has a one-year life cycle in southern Michigan but could require two years to complete a generation in colder regions.
  • Adult emergence usually begins in early June, peaks in late June and early July, and continues into late July.
  • Beetles usually live for about 3 weeks and are present into mid-August.
  • Adult beetles are active during the day, particularly when conditions are warm and sunny.
  • Beetles feed on ash foliage, usually in small, irregularly-shaped patches along the margins of leaves.
  • Females can lay at least 60 to 90 eggs during their lifetime.
  • Eggs hatch in 7 to 10 days.
  • After hatching, first instar larvae chew through the bark and into the cambial region.
  • The S-shaped feeding gallery winds back and forth, becoming progressively wider as the larva grows.
  • Galleries are packed with fine, sawdust-like frass.
  • New adults emerge head-first through a D-shaped exit hole that is 3–4 mm in diameter).
  • Note the characteristic D-shaped exit hole. Once they become adult beetles, they crawl through the bark, leaving these exit holes.
  • EAB larvae choke the Ash tree by eating through the cambium layer just under the bark..

Hosts and Symptoms:

  • In North America, this borer has only attacked ash trees.
  • It is difficult to detect emerald ash borer in newly infested trees.
  • Jagged holes excavated by woodpeckers feeding on pre-pupal larvae may be the first sign that a tree has become infested.
  • When a tree has been infested for at least one year, the D-shaped exit holes left by emerging adults will be present on the branches and the trunk.
  • Bark may split vertically above larval feeding galleries.
  • When the bark is removed from infested trees, the distinct, frass-filled larval tunnels that etch the outer sapwood and phloem are readily visible on the trunk and branches.
  • Serpentine tunnels excavated by feeding larvae interrupt the transport of nutrients and water within the tree during the summer.
  • Foliage wilts and the tree canopy becomes increasingly thin and sparse as branches die. Many trees appear to lose about 30% to 50% of the canopy after 2 years of infestation.
  • Epicormic shoots may arise on the trunk of the tree, often at the margin of live and dead tissue.
  • Dense root sprouting sometimes occurs after trees die.


  • Several insecticide products are available to homeowners for control of emerald ash borer.
  • Treatments are needed every year to protect trees from the Emerald Ash Borer.
  • Treatments are recommended only for homeowners in the quarantined area; it is not necessary to treat ash trees outside of this area.
  • Ash trees need to be in fairly good condition before treatment begins.
  • Fertilize healthy ash trees in the fall and water regularly.
  • Find products containing imidacloprid in your local nursery or garden center.
  • Follow the directions on the label, and apply in May to early June.

Sirex Woodwasp – Sirex noctilio

  • Sirex woodwasp has been the most common species of exotic woodwasp detected at United States ports-of-entry associated with solid wood packing materials.
  • Recent detections of sirex woodwasp outside of port areas in the United States have raised concerns because this insect has the potential to cause significant mortality of pines.
  • Awareness of the symptoms and signs of a sirex woodwasp infestation increases the chance of early detection, and thus, the rapid response needed to contain and manage this exotic forest pest.

Host Trees:

  • North American pine species, especially Monterey pine (P. radiata) and loblolly pine (P. taeda). Other known susceptible pines include slash (P. elliottii), shortleaf (P. echinata), ponderosa (P. ponderosa), lodgepole (P. contorta), and jack (P. banksiana).


  • Sirex woodwasp can attack living pines, while native woodwasps attack only dead and dying trees.
  • At low populations, sirex woodwasp selects suppressed, stressed, and injured trees for egg laying.
  • Foliage of infested trees initially wilts and then changes color from dark green to light green, to yellow, and finally to red during the 3-6 months following attack.
  • Infested trees may have resin beads or dribbles at the egg laying sites, which are more common at the mid-bole level.
  • Larval galleries are tightly packed with very fine sawdust.
  • As adults emerge, they chew round exit holes that vary from 1/8 to 3/8 inch in diameter.


  • Woodwasps (or horntails) are large, robust insects, usually 1.0 to 1.5 inches long.
  • Adults have a spear-shaped plate at the tail end; in addition females have a long ovipositor under this plate.
  • Larvae are creamy white, legless, and have a distinctive dark spine at the rear of the abdomen.
  • More than a dozen species of native horntails occur in North America. No keys to identify woodwasp larvae to the species level have been developed; however, adult specimens have features to distinguish sirex woodwasp from native horntails. Key identifying points include:
    • Dark metallic blue or black body
    • Abdomen of males black at base and tail end, with middle segments orange
    • Reddish-yellow legs
    • Black feet (tarsi)
    • Males with black hind legs
    • Antennae entirely black
  • Positive identification of Sirex noctilio needs to be confirmed by an insect taxonomist. Therefore, collect and submit any suspect woodwasps to your county extension or state Department of Agriculture office.


  • Sirex woodwasp has been successfully managed using biological control agents.
  • The key agent is a parasitic nematode which infects sirex woodwasp larvae, and ultimately sterilizes the adult females.
  • These infected females emerge and lay infertile eggs that are filled with nematodes, which sustain and spread the nematode population.
  • The nematodes effectively regulate the woodwasp population below damaging levels.

Hemlock Woolly Adelgid – Adelges tsugae

Native to Asia, the hemlock woolly adelgid (Adelges tsugae) is a small, aphidlike insect that threatens the health and sustainability of eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) in the Eastern United States.


  • The hemlock woolly adelgid develops and reproduces on all species of hemlock, but only eastern and Carolina hemlock are vulnerable when attacked.
  • The range of eastern hemlock stretches from Nova Scotia to northern Alabama and west to northeastern Minnesota and eastern Kentucky.
  • At least 274 cultivars of eastern hemlock are known to exist.


  • The hemlock woolly adelgid is tiny, less than 1/16-inch (1.5-mm) long, and varies from dark reddish-brown to purplish-black in color.
  • As it matures, it produces a covering of wool-like wax filaments to protect itself and its eggs from natural enemies and prevent them from drying out.
  • This “wool” (ovisac) is most conspicuous when the adelgid is mature and laying eggs.
  • Ovisacs can be readily observed from late fall to early summer on the underside of the outermost branch tips of hemlock trees.

Life History:

  • The hemlock woolly adelgid is parthenogenetic (all individuals are female with asexual reproduction).
  • The adelgid completes two generations a year on hemlocks. The winter generation, the sistens, develops from early summer to midspring of the following year (June–March). The spring generation, the progrediens, develops from spring to early summer (March–June). The generations overlap in mid to late spring.
  • The hemlock woolly adelgid is unusual in that it enters a period of dormancy during the hot summer months. The nymphs during this time period have a tiny halo of woolly wax surrounding their bodies. The adelgids begin to feed once cooler temperatures prevail, usually in October, and continue throughout the winter months.
  • When hatched, the first instar nymphs, called crawlers, search for suitable feeding sites on the twigs at the base of hemlock needles. Once settled, the nymphs begin feeding on the young twig tissue and remain at that location throughout the remainder of their development. Unlike closely related insects that feed on nutrients in sap, the hemlock woolly adelgid feeds on stored starches. These starch reserves are critical to the tree’s growth and long-term survival.
  • Dispersal and movement of hemlock woolly adelgid occur primarily during the first instar crawler stage as a result of wind and by birds, deer, and other forest-dwelling mammals that come in contact with the sticky ovisacs and crawlers. Isolated infestations and long-distance movement of hemlock woolly adelgid, though, most often occur as the result of people transporting infested nursery stock.


  • Cultural, regulatory, chemical, and biological controls can reduce the hemlock woolly adelgid’s rate of spread and protect individual trees.
  • Actions such as moving bird feeders away from hemlocks and removing isolated infested trees from a woodlot can help prevent further infestations.
  • State quarantines help prevent the movement of infested materials into noninfested areas.
  • Chemical control options, such as foliar sprays using horticultural oils and insecticidal soaps, are effective when trees can be saturated to ensure that the insecticide comes in contact with the adelgid.
  • Several systemic insecticides have also proven effective on large trees when applied to the soil around the base of the tree or injected directly into the stem.
  • Chemical control is limited to individual tree treatments in readily accessible, nonenvironmentally sensitive areas; it is not feasible in forests, particularly when large numbers of trees are infested.
  • Chemical treatments offer a short-term solution, and applications may need to be repeated in subsequent years.

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