Beetles - Borers and miners

Borers and miners are the larvae of various insects, particularly beetles, flies and moths. Beetles comprise the largest order of borers. These larvae construct tunnels in terminal shoots, branches, trunks and roots of woody plants of all sizes. Borers can esthetically and/or fatally damage shade, ornamental and fruit trees and shrubs. They are commonly concealed beneath the bark or in the wood, making them difficult to detect and control. Many of the miners that cause damage to annuals, perennials and vegetables as well as woody plants are the larvae of flies. For solutions to problems caused by these pests, see Sawflies - Borers and Miners and Flies - Leaf and Stem miners.

Damage caused by borers often begins in the upper branches of tree crowns and progresses downwards as the tree weakens. Common symptoms include sudden wilting and discoloration of foliage in the tree tops and branch die-back. Infested trees will probably also exhibit D-shaped emergence holes and sinuous or zig-zag patterns in their bark.

Since borers usually prefer to attack weakened trees, good cultural practices that promote high tree vigor and reduce the incidence of disease help to minimize infestations and the resulting damage. Such practices include preventing injury to young trees, watering during dry periods, and appropriate pruning techniques (avoid topping your trees).

Woodpeckers are known to consume borers in large quantities. Attract this natural pest control to your yard by providing suet during cooler months (suet can go rancid in warmer weather and furthermore will mat the birds' feathers).

If borer damage occurs, cut and destroy infested wood by chipping or burning. Since infested trees may die during the first season of attack, you may need to consider use of chemicals to protect particularly valuable trees.

Other images

Click for larger image
Larva of the flatheaded appletree borer larva (Coleoptera). J. Solomon, USFS, Bugwood.org
Click for larger image
Adult flatheaded appletree borer (Coleoptera). N. Wright, FDACS, Bugwood.org
Click for larger image
Larvae and galleries of the twolined chestnut borer (Coleoptera) on oak (Quercus). J. Solomon, USFS, Bugwood.org
Click for larger image
Dieback due to feeding damage of the twolined chestnut borer (Coleoptera). J. O'Brien, USFS, Bugwood.org
Click for larger image
Mandibles are allthat is showing of this beetle borer (Coleoptera) feeding on a dead white pine (Pinus strobus)
Click for larger image
Abdomen and feeding tunnel of a beetle borer (Coleoptera) in a dead white pine (Pinus strobus)
Click for larger image
Not all borers are pests; many borers are part of the decay process, like this beetle borer (Coleoptera) feeding on a dead white pine (Pinus strobus)
Click for larger image
Not all borers are pests; many borers are part of the decay process, like this beetle borer (Coleoptera) that was found feeding on a dead white pine (Pinus strobus)
Click for larger image
An adult blackhorned juniper borer (Coleoptera), Callidium texanum, on its preferred host, freshly cut eastern red cedar (Juniperus) with the bark still on
Click for larger image
An adult blackhorned juniper borer (Coleoptera), Callidium texanum, on eastern red cedar (Juniperus). Note: the holes from which the adult beetles emerged.
Click for larger image
Emergence hole of the adult blackhorned juniper borer (Coleoptera) from eastern red cedar (Juniperus)
Click for larger image
Cutaway showing tunneling in eastern red cedar (Juniperus) by the larvae of the blackhorned juniper borer (Coleoptera)
Click for larger image
View of the tunnels in eastern red cedar (Juniperus) made by feeding of the larvae of the blackhorned juniper borer (Coleoptera)
Click for larger image
Red milkweed beetle (Coleoptera) on milkweed (Asclepias), a common borer of milkweed roots
Click for larger image
Red milkweed beetle (Coleoptera) on milkweed (Asclepias), a common borer of milkweed roots
Click for larger image
Red-headed ash borer (Coleoptera) from ash (Fraxinus)
Click for larger image
Red-headed ash borer (Coleoptera) from ash (Fraxinus)
Click for larger image
Red-headed ash borer (Coleoptera) from ash (Fraxinus)
Click for larger image
Flatheaded borer adult (Coleoptera) found on an oak tree (Quercus)
Click for larger image
This adult spined oak borer Elaphidion lays its eggs on dead oak trees Quercus); it is obviously a type of longhorn beetle (Coleoptera)
Click for larger image
This adult spined oak borer Elaphidion lays its eggs on dead oak trees Quercus); it is obviously a type of longhorn beetle (Coleoptera)
Click for larger image
Buprestis rufipes (Coleoptera), a beetle borer that feeds primarily on maples (Acer), birches (Betula), sourgum (Nyssa), oak (Quercus) and elm (Ulmus)
Click for larger image
Buprestis rufipes (Coleoptera), a metallic beetle borer; note the reddish colored legs
Click for larger image
Underside of Buprestis rufipes (Coleoptera), a metallic beetle borer; note the reddish colored legs
Click for larger image
Honey locust (Gleditsia), pruned and trained to resemble wisteria, is infested with borers (Coleoptera)
Click for larger image
Borer holes (Coleoptera) in a honey locust (Gleditsia) that has been pruned and trained to resemble wisteria
Click for larger image
The leafminer damage on the leaflets of this trumpet vine (Campsis radicans) was caused by beetle larvae (Coleoptera)
Click for larger image
When a twig girdler larva (Coleoptera) is ready to pupate, it chews through the sapwood of twigs, causing the twigs, with the pupa inside, to fall to the ground; shown here on pin oak (Quercus)
Click for larger image
A twig girdler larva (Coleoptera) girdled this pin oak twig (Quercus) then tunneled into the heartwood, plugging the hole behind it.
Click for larger image
Girdled pin oak twig (Quercus) caused by feeding of a beetle known as a twig girdler (Coleoptera)
Click for larger image
Locust borers (Coleoptera) attack only black locust (Robinia pseudoacacia) and its cultivars. Honey locusts are not attacked.
Click for larger image
Dead top (flagging) caused by borers (probably beetles) in Chinese juniper (Juniperus chinensis ‘Fairview’)
Click for larger image
Borer damage in Chinese juniper (Juniperus chinensis ‘Fairview’)