Emerald Ash Borer is an exotic beetle
Emerald Ash Borer, Agrilus planipennis Fairmaire, is an exotic green beetle discovered in Michigan in 2002. This beetle is responsible for killing tens of millions of ash trees in the U.S. and has caused the USDA to enforce quarantines in 12 states, including Missouri and Illinois. The adult beetles nibble on ash foliage, causing little damage. The main damage is caused by the beetle larvae, which feed on the tree’s inner bark, disrupting the tree’s ability to transport water and nutrients.
What trees and shrubs are affected?
- Ash Trees
- The canopy of infested trees begins to thin above infested portions of the trunk and major branches. Heavily infested trees exhibit canopy dieback usually starting at the top of the tree. One-third to one-half of the branches may die in one year. Most of the canopy will be dead within 2 years of when symptoms are first observed. Sometimes ash trees push out sprouts from the trunk after the upper portions of the tree dies. Although difficult to see, the adult beetles leave a "D"-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they emerge in June.
The beetle can have a one- or two-year lifecycle. Adults begin emerging in mid- to late May with peak emergence in late June. Females usually begin laying eggs about 2 weeks after emergence. Eggs hatch in 1-2 weeks, and the tiny larvae bore through the bark and into the cambium -- the area between the bark and wood where nutrient levels are high. The larvae feed under the bark for several weeks, usually from late July through October. The larvae typically pass through four stages, eventually reaching a size of roughly 1 to 1.25 inches long. Most EAB larvae overwinter in a small chamber in the outer bark or in the outer inch of wood. Pupation occurs in spring and the new generation of adults will emerge in May or early June, to begin the cycle again.
Solution
Experts do not recommend treatment of a tree with more than 20% dieback of its canopy. Treatments should be considered mainly for prevention. Currently no treatments have been proven effective against EAB. Treatments usually require annual applications. Other preventative measures include:
Don’t move firewood. Emerald ash borer travels in firewood. Many infestations were started when people moved infested ash nursery trees, logs or firewood into uninfested areas. Shipments of ash nursery trees and ash logs with bark are now regulated, and transporting firewood outside of the quarantined areas is illegal, but transport of infested firewood remains a problem. The easiest way to keep it from spreading is to avoid buying wood that is sold more than 50 miles from the place it was cut. If you burn firewood in your home stove or use it for camping, cut and burn your own or make sure the wood you buy comes from a local forest.
Don't plant ash trees. EAB feeds exclusively on ash trees. If you deprive them of food, they can't survive. Choose from any number of other suitable hardwoods for shade, habitat and timber.
