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Plantwise Technical Factsheet

emerald ash borer (Agrilus planipennis)

Host plants / species affected
Chionanthus virginicus (white fringe tree)
Fraxinus americana (white ash)
Fraxinus chinensis (chinese ash)
Fraxinus excelsior (ash)
Fraxinus lanuginosa
Fraxinus mandshurica (Manchurian ash)
Fraxinus nigra (black ash)
Fraxinus pennsylvanica (downy ash)
Fraxinus profunda (Pumpkin ash)
Fraxinus quadrangulata (Blue ash)
Fraxinus rhynchophylla
Fraxinus velutina (velvet ash)
Juglans mandshurica (Manchurian walnut)
Pterocarya rhoifolia (japanese wing nut)
Ulmus davidiana (japanese elm)
List of symptoms/signs
Leaves  -  abnormal colours
Stems  -  dieback
Stems  -  internal feeding
Whole plant  -  internal feeding
Whole plant  -  plant dead; dieback
Symptoms

The larvae make long serpentine galleries (up to 26-32 mm long) into the sapwood, which enlarge as they grow and are filled with brownish sawdust and frass. Callus tissue produced by the tree in response to larval feeding may cause vertical splits, 5-10 cm long, in the bark above a gallery. Newly emerged adults bore 'D'-shaped (3-4 mm diameter) exit holes on trunks and branches. As the larvae damage the vascular system, attacks cause general yellowing and thinning of the foliage, dying of branches, crown dieback and eventually death of the tree after 2 to 3 years of infestation. Basal sprouting and also the presence of woodpeckers may indicate wood-boring beetle activity. After 1 to 2 years of infestation, the bark often falls off in pieces from damaged trees, exposing the insect galleries.

Prevention and control

Since the discovery of A. planipennis in North America in 2002, various control methods have been studied and implemented.

Silvicultural Methods

In North America and Europe, A. planipennis attacks and kills healthy trees. Thus, the silvicultural methods to maintain or enhance tree vigour, which are usually applied to prevent the attack of most bark and wood-boring insects are of little value.

To prevent the emergence of adults from dead or cut trees, mechanical destruction of infested trees through chipping, grinding or heat treatment is recommended (McCullough et al., 2007).

Chemical Control

Insecticides can be sprayed on cut logs to kill adults at emergence and sanitize infested logs (Petrice and Haack, 2006). Cover sprays and trunk or soil injections of insecticides can also be used to protect high value urban and shade trees within the quarantined areas, although annual treatments are usually required (Poland, 2007). Effectiveness depends on insecticide products, injection methods, timing tree size and the extent of previous injury. No insecticide seems to provide 100% control, but ash trees can tolerate minor damage by the beetle. In woodland and forested areas, insecticidal control is neither economically viable nor environmentally desirable (Cappaert et al., 2005; Poland and McCullough, 2006).

Biological Control

Three parasitoid species were collected in China, determined to have adequate specificity, and released in North America: the egg parasitoid Oobius agrili and two larval parasitoids, Tetrastichus planipennisi and Spathius agrili (Bauer et al., 2007). At least O. agrili and S. agrili seem to have become established (Bauer et al., 2008) but impacts of the parasitoids have not yet been determined.

The fungus Beauveria bassiana has been found to be highly virulent against A. planipennis, and demonstrated lethal effects in greenhouse and field trials when applied on emerging adults and larvae (Liu and Bauer, 2008a). Foliar and trunk applications in the field were also able to significantly reduce populations of A. planipennis both at newly colonised ash sites and at sites with established pest populations (Liu and Bauer, 2008b).

Phytosanitary Measures

In the USA and Canada, movement of ash material from infested areas is regulated by federal quarantine regulations. Prohibited material includes ash trees, limbs or cut firewood, ash logs and lumber, uncomposted ash wood chips and bark chips larger than 1 inch in diameter. In Michigan, sale or transport of ash nursery trees is prohibited state-wide, and transport of any non-coniferous firewood out of the quarantined counties is prohibited as well (Poland and McCullough, 2006). In various regions in the USA and Canada, eradication cuts have been carried out at outlier sites, consisting of the cutting and shipping of all ash trees within a certain distance of infested trees (Poland and McCullough, 2006; Poland, 2007).

Current regulations, following the IPPC International Standards for Phytosanitary Measures No. 15, require that solid wood packaging material be heat treated or fumigated prior to export.

Impact

Related treatment support
 
External factsheets
USDA-NAL National Invasive Species Information Center Species Profiles, USDA-NAL National Invasive Species Information Center (NISIC), 2012, English language
Maine Forest Service Insect and Disease Factsheets, Maine Department of Conservation, 2012, English language
Ohio State University Extension Fact Sheets, The Ohio State University Extension, English language
British Columbia Ministry of Agriculture Factsheets, Government of British Columbia, English language
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