Emerald ash borer

Order: Coleoptera
Family: Buprestidae
Latin: Agrilus planipennis Fairmaire
English: Emerald ash borer
French: Agrile du frêne

Control

Laws

This insect is one of the pests regulated by the Canadian government and is the subject of the following policy directives:

Directives

D-98-08: Entry Requirements for Wood Packaging Materials Produced in All Areas Other than the Continental United States
D-02-02: Plant Protection Import Requirements for Rooted, or Unrooted Plants, Plant Parts, and Plants In Vitro for Planting
D-02-12: Import requirements of non-manufactured wood and other non-propagative wood products, except solid wood packaging material, from all areas other than the continental United States
D-03-08: Phytosanitary Requirements to Prevent the Introduction into and Spread Within Canada of the Emerald Ash Borer, Agrilus planipennis (Fairmaire)

Prevention

Canadian and U.S. authorities have given up the strategy of trying to eradicate the emerald ash borer and instead are turning to measures to accommodate and manage this pest (Bauer et al. 2008). Quarantine measures coupled with better detection techniques (Lyons et al. 2007) may prevent small infestation centres from spreading. To date, the main pathway for the spread of the insect appears to be the transport of infested materials, nursery stock and natural dispersal (CFIA 2008; Anonymous 2008; Liu and Bauer 2008).

Control

1. Mechanical and silvicultural

Cutting down infested trees and burning or burying the wood can help reduce emerald ash borer populations and slow their spread, particularly when infestation centres are small. Salvage cutting of affected trees in woodlots within regulated areas can be done but it is expensive. Logs can be cut up since the borer does not penetrate very deeply into the wood but whole logs must not be taken out of regulated areas and all residues must be destroyed.

2. Chemical

The systemic insecticide imidacloprid, applied either through trunk injections or soil drenching, has been tested in the United States (GISD 2008). Emamectin benzoate is another systemic insecticide that has shown some promise in the United States. Special permission from the authorities for its use in Michigan, Indiana, Ohio, Illinois and West Virginia was obtained in 2007 (Anonymous 2008).

In Canada three active ingredients are registered for controlling the emerald ash borer by trunk injection : acephate, imidacloprid and azadirachtin.

Caution
There are many different chemical pest control products available. They may be toxic to plants, animals, humans or the environment in general. A number of these products pose potentially lethal risks to humans. To protect human health and the environment from pesticide-related risks, Canada adopted the Pest Control Products Act (PCPA). The Pest Management Regulatory Agency (PMRA; http://www.hc-sc.gc.ca/ahc-asc/branch-dirgen/pmra-arla/index-eng.php) is responsible for administering the Act. A pesticide product label indicates the class designation (domestic, commercial, agricultural), the potential risks to human health and the environment, and the conditions and restrictions pertaining to product use. Compliance with the label directions and restrictions is mandatory. The provinces may also regulate the use of pesticides within their respective territory. For more information on these products, contact PMRA at the following E-mail address: pmra.infoserv@hc-sc.gc.ca

3. Biological

Spraying the trunk and foliage with the entomopathogenic fungus Beauveria bassiana strain GHA (only strain HF 23 is registered in Canada) has shown promise when applied before adult emergence (Liu and Bauer 2008). However, there are not enough data to assess how well this product protects trees from emerald ash borer attack (GISD 2008)
Two parasitoids, Tetrastichus planipennisi and Spathius agrili, were released in Michigan in 2007 to improve the very low parasitism rates observed in the United States (Bauer et al. 2008). It is still too early to assess the effectiveness of these biological control agents. Studies on another parasitoid (Hui et al. 2008) are under way.

4. Genetic resistance

The hybridization of North American ashes with Asian species could produce trees more able to resist attack by the emerald ash borer (Rebek et al. 2008).

5. Stages in an integrated disease management program

Studies are under way on establishing an integrated management strategy for the emerald ash borer. The use of parasitoids, already attempted in Michigan, is promising but we will have to wait for results from recaptures and parasitism measurements before determining how effective these measures actually are. Although the entomopathogenic fungus Beauveria bassiana strain GHA provides an alternative to pesticides, its effectiveness in preventing attacks remains to be seen. Promising systemic insecticides are already available on the U.S. market and allow ornamental trees to be saved.Control cannot be achieved at the stand scale. Infested trees still have value on the pulp and lumber markets since the emerald ash borer only attacks the outer layers of the sapwood. In regulated areas, usable trees can be sawn on site with a portable sawmill. Logging and sawmill residues must be burned, chipped or buried. Before proceeding, operators must contact the Canadian Food Inspection Agency (Rose et al. 2006).
For ornamental trees, Rebek and Smitley 2007 recommend that the following treatments should only be done if the trees are in a quarantined area:

Maintain trees in overall good health by fertilizing them and watering them during dry periods.
Infested trees exhibiting between 20% and 40% dieback can be treated with acéphate systemic insecticide.
Trees with over 40% dieback should be felled.
Trees with a greater diameter should be treated annually.

References