Pest type: Insects
Emerald ash borer (EAB), a beetle from Asia that feeds on ash trees, was discovered as the cause of extensive ash mortality in southeast Michigan and adjacent areas of Canada in 2002. It is thought that this destructive pest was introduced in the early 1990’s in infested solid wood packing material originating in Asia. Ash trees are widespread in the United States and all 16 native ash species are susceptible to attack. EAB now affects Ash trees in Michigan, Arkansas, Colorado, Connecticut, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Massachusetts, Minnesota, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, Wisconsin, Ontario and Quebec.
EAB adults begin to emerge from ash trees after the accumulation of 400-500 growing degree days (GDD) base 50°F. Peak adult activity occurs at ~1,000 GDD. After emergence, adults fly into the ash canopy where they feed on leaves throughout their lives. EAB adults start mating one week after emergence, and females begin laying eggs 2-3 weeks later.
A female EAB may lay >200 eggs in her lifetime, depositing them individually or in groups on the bark along the trunk and portions of the major branches. Eggs are laid in areas where the bark is rough, and between bark layers or in bark crevices. Eggs are approximately 1.0 mm long x 0.6 mm wide and creamy white when laid; fertile eggs gradually turn amber after a few days. The eggs hatch after about two to three weeks.
Newly hatched larvae bore through the bark to the phloem and outer layer of new sapwood where they feed until the weather gets too cold in the fall. There are four stages of larval development (instars). As they feed, the larvae create serpentine galleries filled with frass, which enlarge in width as the larvae grow. Larvae are creamy white, and dorso-ventrally flattened. When fully mature, fourth-instar larvae are 26 to 32 mm long. Their head is mostly retracted with only the dark brown mouthparts visible.
EAB is a significant threat to our urban, suburban, and rural forests as it kills stressed and healthy ash trees. EAB is so aggressive that ash trees may die within two or three years after they become infested. Ash trees are as important ecologically as they are economically in the forests of the eastern United States. Ash trees fill gaps in forests and are highly desirable for urban tree planting. Ash wood is valued for flooring, furniture, sports equipment (e.g., baseball bats, hockey sticks, and oars), tool handles, and supplies for dairies, poultry operations, and beekeepers. Ash trees and ash wood are also significant to Native American cultures for traditional crafts and ceremonies.
Don't move firewood. EAB larvae can survive hidden in the bark of firewood. Remember: buy local, burn local. Inspect your trees. If you see any sign or symptom of an EAB infestation, contact your State agriculture agency. Talk to friends, neighbors and co-workers about EAB and what they should be aware of on their trees. Ask questions. If you receive ash nursery stock or firewood, know its point of origin and your supplier, as larvae could be hiding under the bark. Know State and Federal regulations. Make sure you understand regulations that govern your state and those you may visit.
Ash trees with low population densities of EAB often have few or no external symptoms of infestation. Symptoms of an infestation may include any or all of the following: dead branches near the top of a tree, leafy shoots sprouting from the trunk, bark splits exposing larval galleries, extensive woodpecker activity, and D-shaped exit holes.
Removal of ash trees is the most effective control method to stop the spread of the pest to other areas. You can replace ash trees with an appropriate native species.
Encourage biodiversity. Woodpeckers hunt for both the larvae and pupae, the last life cycle stage before the insect turns into an adult beetle, emerges from the tree and starts all over again. Researchers from the University of Illinois at Chicago found that woodpeckers are feeding on the pest. They also concluded that a native insect fighter such as the woodpecker is better than using chemicals to kill the pest. Chemicals are expensive and can damage the environment
Early in the EAB program, USDA’s Animal and Plant Health Inspection Service (APHIS) and the Forest Service (FS) initiated a search for potential biological control agents in The People’s Republic of China. Three potential biological control agents were identified; Spathius agrili, Tetrastichus planipennisi, and Oobius agrili. Since 2007, releases of these stingless wasps show promise as a long-term management strategy. USDA researchers conclude, “At present, the most sustainable and long-term approach to reducing EAB populations and conserving ash in forested areas of North America is biological control. Efforts are ongoing to find and evaluate additional biological control agents.
Unfortunately, these biological control options are not widely available to the public (individual homeowners). Municipalities can reach out to APHIS to see whether their city can become part of a release program. Guidelines for APHIS biocontrol releases can be found here. The first step is to get a release permit from APHIS. A city can apply for a permit here (see “Guidelines and Regulations for the Importation of Pests and Organisms).” Permitting takes roughly 4 to 6 months.
Azadirachtin, which is derived from neem, has a relatively short half-life and is less toxic to bees than the synthetic, systemic chemicals often used to treat EAB. Yet, there is some evidence of reproductive toxicity associated with exposure to bumblebees, and indications that they can be negatively affected by the chemical even at levels significantly lower than recommended levels. However, if it is applied after ash trees bloom, the likelihood of affecting pollinators would be reduced. Any pesticide use, either least-toxic or synthetic, is simply a delaying tactic. Even with treatment, EAB is likely to irreparably damage ash trees within 5 years, and kill them within 10.
Look at your product labels and try to avoid products containing those chemicals listed below:
(A = acute health effects, C = chronic health effects, SW = surface water contaminant, GW = ground water contaminant, W = wildlife poison, B = bee poison, LT = long-range transport)
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