Elm Borer

Elm Borer, Pests of Trees and Shrubs one generation a year. This beetle is found in the eastern region of the united states NY, NJ, Connecticut.

Adult moths are light brown, 25 mm long,with two diagonal white stripes across the forewings.Wingspan is 37–50 mm. Larvae can grow to 50 mm or more in length. They have black heads, a white stripe down the length of the back and yellow lateral stripes with blue spots.Overwintered eggs hatch as host tree buds begin to unfold in the spring. Larvae are gregarious and construct a communal web or tent, which grows as they develop and from which they emerge to feed.

Life Cycle:Elm Borer larvae are white with a long (about one inch when mature) narrow, segmented abdomen that is also flattened, which gives them the appearance of small tapeworms. Adults are elongate, 1/2-inch-long beetles with striking, metallic-green coloration. Adult beetles emerge from infested ash trees in late May through early August, with emergence peaking in mid to late June.As adults emerge, they leave small, distinctly D-shaped exit holes in the trunk and main branches. Adults may live three to six weeks and nibble on small patches of ash leaves during this period.

Females generally produce 50 to 80 reddish eggs, which are laid individually on the bark surface, or within bark cracks and crevices. When the larvae hatch, they tunnel into the tree, where they feed on the phloem and outer sapwood, excavating S-shaped, serpentine galleries just under the bark.

The galleries disrupt the flow of nutrients and water between the canopy and roots. This causes canopy thinning and branch dieback, and ultimately tree death.Larvae continue to feed through the summer and into the fall. They overwinter in the outer bark or within the outer inch of sapwood. Pupation occurs in mid to late spring. Adults emerge soon thereafter to complete the typical one-year lifecycle.

Damage: The first, visual inspections has proved ineffectual. The second, trap trees, is expensive and time consuming. Emerald ash borer prefers to attack stressed trees, attracted by the chemicals produced, but will readily attack healthy ones as populations build. The creation of a trap tree involves girdling a healthy ash in the spring. Green ash, Fraxinus pennsylvanica, is used most often. This provides the beetle with ideal host material. Tree placement occurs on a grid with trap density increased around higher risk areas such as sawmills, campgrounds, and tree nurseries. During the winter, trap trees are peeled and examined for evidence of beetle larvae or galleries.

The procedure works but the method is also problematic. Suitable host material is not always available and when it is, the method certainly is destructive. The numbers of trees to be examined may run into the thousands. When eradication was the goal, protocol called for the removal, chipping and burning of all ash within half a mile of any identified beetle tree and costs per site ran between $500,000 and $1,000,000.

These protocols are followed now only when sites are located so early that the beetle population is small and there is little ash on site. The beetle flies much farther than the half-mile treatment boundary although it probably will not if suitable host material remains nearer. A third detection method, currently the method of choice by most state and federal agencies, involves the use of a purple panel trap, a large triangular boxlike structure without top or bottom. The color is attractive to the beetle and the trap’s attractiveness is usually enhanced with a chemical attractant.

Control: In the dormant season, prune and destroy egg masses. Destroy webs and their contents as soon as they appear.Use Bacillus thuringiensis var. kurstaki when trees are flowering to protect pollinating bees.Spray foliage when tents first appear. A diverse assemblage of parasitoids and predators attack this highly conspicuous species.These include parasitic wasps Hyposoter spp.(Ichneumonidae) and Bracon spp. (Braconidae), tachinid flies, hornets, yellow jackets, ants, predatory stink bugs,and birds. Epizootics of an NPV virus decimate popula-tions in peak years.

when the beetle arrives, the landowner has few options. Individual, high value trees can be protected with an insecticide. These treatments have to be repeated regularly and should a beetle tree be located within a designated area and an eradication cut performed, the treated tree would be removed. Removal and utilization of ash, particularly larger diameter ash from woodlots retards population buildup because the larger the tree, the more beetles that tree is capable of feeding. Ash value, already diminished, will probably continue to shrink. Once the beetle arrives in New York options available to the forest owner will also shrink due to quarantine. The picture is bleak. Emerald ash borer continues to devastate ash in this country and it is headed our way.

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