Insecticide For Trees

Tree borers are wood-boring beetles, primarily known for destroying the trees in your yard. Without the right precautions, there is no way to prevent tree borers from gnawing away at your prized trees and shrubs. To prevent infestations of these destructive insects, professional insecticide treatment is usually necessary.

Insecticide For Trees

Most insect borers are attracted to weakened, damaged, dying or dead plants. These are referred to as “secondary invaders” because they attack only after a plant has been weakened by another stress. Secondary invaders are a symptom of other problems with the health of the tree or shrub, but may contribute to its decline. Secondary invaders include species from groups already mentioned, but also may include termites, carpenter bees and carpenter ants.

Many other insects live in dying or dead trees, including natural enemies (predators and parasites) of the insect borers, sap or fungi feeders, or species which merely use the spaces provided by the tunnels and galleries as living quarters.

Wood-boring insects that attack healthy trees and shrubs are called “primary invaders.” Primary invaders may eventually kill trees.

Damage

Borer infestations often go unnoticed until plants or parts of plants begin to die or show external signs of damage. Wood-boring insects often produce sawdust-like frass (excrement). Their holes are normally round, oval or semicircular and are found in a random pattern on the plant. Woodpecker damage is sometimes confused with that of wood-boring beetles; however, woodpecker damage will not produce frass. One woodpecker, the yellow-bellied sapsucker, produces square holes in rows around a trunk or branch.

Borers tunnel in the inner bark layer (cambium), which transports nutrients and water to the leaves. When the cambium layer is completely girdled the plant eventually dies above or beyond the damage site. Partial girdling reduces plant growth and vigor above the site of attack. On occasion, tunneling makes the tree weak, causing limbs and branches to fall. Borer damage can severely affect the quality of lumber and can make trees susceptible to disease.

Wood-boring Insects

Long-horned beetles or round-headed borers (Coleoptera: Cerambycidae)

Adults are called long-horned beetles (Fig. 1) because their antennae are occasionally longer than their bodies. Larvae tunnel underneath bark and into the heartwood. The tunnels are oval to almost round in cross section because of the round shape of the larvae (Fig. 2). Larvae of some species are legless, but most have three pairs of small legs on the first three segments behind the head capsule. While tunneling, larvae continually pack their tunnels with excrement (frass), which looks like compressed wood fibers, or push frass out of the holes they produce. This excrement, along with the sap exuded by the plant in response to the damage, is often visible on the outside of infested trunks or branches. Many species of beetles belong to this group, but most are secondary invaders. Some examples of long-horned beetles are described below.

Locust borer (Megacyllene robiniae) adults are medium-sized (3 ⁄4 inch long) long-horned beetles frequently found feeding on goldenrod or other flowers in the fall. They are dark brown to black with distinctive gold-yellow markings. Larvae hatch from eggs laid in bark crevices. Visible symptoms of infestation are wet spots and frass on the bark of black locusts. Later, larvae tunnel into the inner bark and construct cells in which they spend the winter months. In a year the larvae are fully grown and about an inch in length.

Cottonwood borer (Plectrodera scalator) is frequently found on cottonwood, poplar or willow trees. Adult beetles are large (11 ⁄4 inches long) with an attractive black and whitish-yellow pattern. They are active from May through August. The larvae (1.75 to 2 inches long) tunnel at the base of the trunk or below ground level. They require about 2 years to develop.

Red-headed ash borer (Neoclytus acuminatus) is one of the most common wood-boring beetles. It has a narrow body with a reddish thorax and light brown wing covers marked with four yellow lines on each. The yellow lines are slanted downward toward the middle, giving the appearance of a “V” across the back. The antennae are rather short and the long legs are thin and fragile. Redheaded ash borers feed in many species of wood including ash, oak, elm and even grapes. Adults can be found on dead log piles and frequently emerge from firewood.

Red oak borer (Enaphalodes rufulus) attacks oak and maple trees and can be a serious pest in nurseries. The reddish-brown adults ( 5 ⁄8 to 11 ⁄8 inches long) lay eggs individually in bark crevices during July and August. Larvae tunnel under the bark and into the heartwood. Infested sites can be recognized by the frass around the buckled bark near the gallery entrance. Larvae often tunnel completely around the trunk or branches they infest, producing noticeable scars or girdling. Red oak borers feed for more than a year before pupating in chambers tunnelled into the heartwood. Damage kills limbs or terminals and increases the risk from secondary invaders and diseases.

Twig girdler (Oncideres species) damage occurs primarily from egg laying. This insect attacks pecan, mimosa, chinaberry and huisache. The grayish-brown adults (11 ⁄16 inch long) girdle limbs during the fall (late August through mid November) by chewing a V-shaped groove entirely around twigs, branches or terminals. Eggs are inserted into the bark on the girdled part of the branch away from the tree. Girdled limbs eventually break and fall to the ground, particularly during high winds and storms. Damage can disfigure a young tree and leads to secondary branching, particularly if the terminal is attacked. Larvae reach up to 7 ⁄8 inch long and are unable to develop in healthy sapwood. Removing the girdled twigs and branches from the ground during winter and spring and destroying them can reduce the population of these insects.

Twig and branch pruners (Elaphidionoides and Agrilus species) produce damage superficially similar to that of twig girdlers on elm, hackberry, hickory, maple, oak, pecan, persimmon, redbud, sweetgum and other trees. In these species, however, it is the larvae that girdle twigs and branches underneath the bark. The surface of the severed end of the twig is smooth. The insect usually severs branches where small twigs branch from the main, girdled branch.

Metallic wood-boring beetles (or flat-headed borers) (Coleoptera: Buprestidae)

Adult beetles are flattened, hard-bodied and boatshaped with short antennae. These are beautiful beetles with distinctive metallic colors (green, blue, bronze, copper). Larvae are cream-colored and legless with widened, flattened body segments just behind the heads. Consequently, when these larvae tunnel beneath bark or into the sapwood they produce oval or flattened tunnels in cross section (Fig. 2). Galleries are often winding and packed with frass. Tunneling can girdle trunks and branches. Many species of flat-headed borers occur in the state. Most are secondary invaders.

Examples of flat-headed borers include the bronze birch borer (Agrilus anxius), uncommon in Texas because of the lack of host trees; Agrilus species found on oak and raspberry (A. bilineatus and A. ruficollis, respectively); flat-headed appletree borer (Chrysobothris femorata) and a closely related species that attacks recently transplanted or stressed shade, pecan and fruit trees.

Bark beetles (Coleoptera: Curculionidae)

Beetles in this group tunnel below the bark of trees and/or into the wood. Adult beetles are small and reddish-brown to black. Larvae are creamcolored grubs without legs. One member of this group, the European elm bark beetle (Scolytus multistriatus), is the carrier of Dutch elm disease. It occurs in the Texas Panhandle, but is infrequently encountered in other parts of Texas. Other members of this group are described below.

Southern pine beetle (Dendroctonus frontalis) is a primary pest of southern pine forests. Adult beetles are active during warmer months (when temperatures are above 58 degrees F), and disperse widely to injured, weakened or stressed trees in the spring. Seven or more generations may be completed within a year. When abundant, they can attack healthy trees. Larvae tunnel beneath the bark producing tunnels or galleries in patterns resembling the letter “S” (Fig. 5). This tunnelling quickly disrupts the cambium layer, girdling the tree. Infested trees can have numerous masses of resin called “pitch tubes” on the tree trunk. Needles of newly attacked trees turn reddish brown 1 to 2 months after infestation during the summer, and up to 3 months afterward in the winter. Removal and destruction of infested trees may prevent healthy trees in the vicinity from being attacked.

Ips engravers (Ips. spp.) are often mistaken for the southern pine bark beetle because their appearance and damage are similar. Their gallery patterns tend to be more parallel to each other, however (Fig. 5). Ips usually attack weakened trees only. Recently felled wood should be covered with plastic to prevent Ips beetle infestation. The black turpentine beetle, Dendroctonus tenebrans, is another species attacking pines.

Shothole borers (Scolytus rugulosus) are secondary pests of common fruit trees (peach and plum), wild plums and occasionally ash, elms and hawthorne. These bark beetles tunnel through the bark and make small holes in the bark crevices.

Granulate ambrosia beetle (Xylosandrus crassiusculus) is a newly introduced species that attacks healthy, stressed or freshly cut elm, pecan, peach, Prunus species, oak, sweetgum and other trees in east Texas. Tiny (2 to 3 millimeters long), dark reddish-brown adult female beetles tunnel into twigs, branches or small tree trunks, excavating a system of tunnels in the wood or pith in which they lay eggs. They also introduce a fungus on which the larvae feed. Visible damage includes wilted leaves on infested branches and protrusions of compressed wood dust from numerous small holes, resembling toothpicks pointing outward. Dead and dying areas of bark (cankers) can form at the damage site, eventually girdling the tree and killing it. There are several generations per year. Chemical control of this species has been generally unsuccessful. Native ambrosia beetles are also called shot-hole or pine-hole borers. These species have similar biologies but rarely attack healthy, vigorous trees.

Weevils (Coleoptera: Curculionidae)

Adult weevils have a characteristic snout that bears the chewing mouthparts (Fig. 6). Larvae are legless and cream-colored, and generally feed in cells or hollowed out cavities underneath the bark rather than in galleries or tunnels as do bark beetles. Virginia pine plantings in Texas have suffered extensive damage from the deodar weevil, Pissodes nemorensis. These weevils attack the trunks during the winter, where young trees are in poor planting sites. Several weevil species attack the bases and roots of woody ornamental plants.

Wood-boring caterpillars (Lepidoptera)

These insects are the immature stages of several kinds of moths. Caterpillars can be easily identified by their “false legs” (prolegs) with tiny rows of 4 Figure 5. Left to right: “S”-shaped egg galleries of the Southern pine beetle; “Y”- or “H”-shaped egg galleries of the Ips engraver beetles. Protrusions of compressed wood dust signal attack by the granulate ambrosia beetle. Figure 6. Deodar weevil larva, pupa and adult. hooks on the undersides of some of the abdominal segments (Fig. 7). Adult moths are rarely seen except when reared from the host plants or collected in blacklight traps. Several kinds of moth larvae tunnel into woody ornamental plants:

Carpenterworms (Prionoxystus robinae) are large larvae that tunnel through the trunks of oak, elm, black locust, willow, ash, boxelder, poplar, cottonwood, Chinese tallow and fruit trees such as pear and cherry. These larvae develop over 2 or 3 years, initially feeding underneath the bark but later tunnelling into the heartwood. Outward signs of attack include piles of sawdust and excrement, particularly in cracks and crevices. Carpenterworms may enter and exit the trunk of the tree several times during their development. Several closely related species with similar life cycles also occur in Texas, but may develop in other host trees. Adult moths, which emerge in the spring, are rather large with spotted wings.

Peach tree borer (Synanthedon exitiosa) is one of the most important insect pests of peach and plum. Adult peach tree borer moths mate and lay their eggs on the trunks of peach and plum (Prunus species) trees during August and September. These daytime fliers are one of several species often called clear-wing moths, and they look superficially like wasps (Fig. 7). Larvae hatch from eggs in about 10 days and tunnel beneath the bark for 10 to 11 months before emerging from the base of the trunk. Infected trees exhibit dieback, yellowing of leaves, stunted growth and possible death if larvae girdle the trunk near the soil line (from 10 inches above the ground to 3 inches below the ground). After emerging, they drop to the soil to pupate at the base of the tree. Affected trees can be identified by masses of sap around damage sites at the base of the trunk. Infestations can kill scaffolding limbs or entire trees.

Other species of clearwing moths are: 1) the lilac or ash borer (Podosesia syringae), which has its adult flight period during the spring and early summer; 2) the dogwood borer (Synanthedon scitula); and 3) the lesser peach tree borer (Synanthedon pictipes).

Other caterpillar pests that occur in Texas include: the southern pine coneworm (Dioryctria amatella), which tunnels around the bases of Virginia pine trunks (Fig. 8); Euzophera ostricolorella, a root collar borer that infests potted magnolia; and the American plum borer (Euzophera semifuneralis), which invades damaged or improperly pruned branches on a wide variety of woody ornamentals.

Managing Wood-boring Insects

Prevention
Since most wood-boring insects are considered secondary invaders, the first line of defense against infestation is to keep plants healthy. Proper care of trees and shrubs discourages many borer pests and helps infested plants survive. Good sap flow from healthy, vigorously growing trees, for example, defends the plant from damage by many borer pests. Good horticultural practices include:

• Selecting well adapted species of trees and shrubs that are not commonly attacked by wood borers in your area. Arizona ash, birch, cottonwood, locust, soft maple, flowering stone fruits (such as peaches and plums), slash pines (in west Texas), willow and poplar are especially prone to borer attack.
• Choosing and preparing a good planting site to avoid plant stress, freeze damage, sun scald and wind burn.
• Minimizing plant stress and stimulating growth by using proper watering and fertilization practices.
• Avoiding injury to tree trunks from lawn mowers, weed trimmers or construction.
• Promptly caring for wounded or broken plant parts using pruning or wound paint during all but the coldest months of the year.
• Properly thinning and pruning during colder months.
• Removing and destroying infested, dying or dead plants or plant parts, including fallen limbs. Wrapping tree trunks and limbs with quarter inch hardware cloth spaced about 1 ½ inches from the tree’s surface where woodpecker damage is likely.

Wrapping trunks to prevent borer attack is ineffective and may, under certain conditions, increase the rate of infestation. Using plastic trunk protectors to help prevent injury from lawn mowers and weed trimmers is a good idea.

Non-chemical control for infested plants

Once trees and shrubs are infested, non-chemical options for borer control are limited. One option is to remove and destroy heavily infested or injured plants. Also, inspect damage sites closely to determine if the larvae can be extracted from the plant with a pocket knife, wire or other suitable tool.

Chemical control

Because stressed, unhealthy trees are more susceptible to insect attack, maintaining overall tree health is vital in reducing the risk of wood-boring insect infestations and limiting the need for costly and environmentally damaging insecticides. Older trees and those damaged by drought or other environmental stress also will not benefit from control efforts.

Table 1 lists some insecticides registered by the Environmental Protection Agency (EPA) for wood boring insect control on trees and shrubs. Some of these products are for professional or commercial use only and not available at retail outlets. In addition, the product labels specify where the product is to be used, such as nurseries or landscapes, and which pest or pest category it targets. Choose products according to the labeled restrictions. Do not use insecticides on fruit or nut trees unless specifically labeled for them. Some products sold mainly through specialty stores may require the purchaser to have a Texas Department of Agriculture pesticide applicator’s license.

Application timing and method also may be specified on the label. Some products are preventive only; others are to be used during the target pest’s adult flight periods. Bark sprays target egg-laying females or the adult stages emerging from the host plant. They also may kill small larvae. Bark sprays generally use residual insecticides such as carbaryl or pyrethroid insecticides such as bifenthrin or permethrin. Only a few products are effective on larvae tunneling beneath the bark, such as that of the flatheaded borer beetles. These systemic products usually are applied as soil drenches so the insecticide can be absorbed by the roots or injected into the trunk; the insecticide imidacloprid is applied as either a soil drench or a trunk injection. Dinotefuran also may provide some control of wood-boring beetles.

Retail sale of diazinon, chlorpyrifos (Dursban®) and endosulfan (Thiodan®) products have been discontinued. Diazinon and lindane are no longer available for insect control and chlorpyrifos is available only for use in commercial nurseries. Products containing these ingredients may still be used according to label directions if you first contact the manufacturer to ascertain that usage is allowed. Otherwise they should be disposed of using directions provided by city, county or state pesticide authorities.

Only a few products for controlling wood-boring insects are available at retail stores. Occasionally these products’ containers have labels that are taped to the container and cannot be read before purchase. The products’ names may indicate target pests, such as Fertilome® Borer, Bagworm, Tent Caterpillar & Leafminer Spray, but the actual label has use directions for only the peach twig borer (a caterpillar of a clearwing moth species) on fruit trees. In other cases, lists of pests on products that are available only to commercial applicators are more extensive than those on products available to homeowners, such as those containing the pyrethroid insecticides, bifenthrin and permethrin.

Insecticide For Trees

Tree borers are insects that attack trees by tunneling through the bark, which causes the tree to become weak and die. They can also kill a tree by tunneling into the cambium layer and causing sap to flow from the wound, which attracts predators and eventually kills the tree.

Tree borers are usually small, but they can cause significant damage.

There are many different types of borers, including:

– Moth borer

– Cankerworm

– Gypsy moth larvae

– Emerald ash borer larvae

List Of Insecticide For Trees