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insecticide up the trunk and into the branches and canopy. When EAB larvae feed, their gai- leries injure the phloem and xylem that make up the plant's circulatory system. This inter- feres with the ability of the tree to transport nutrients and water, as well as insecticides. As a tree becomes more and more infested, the injury becomes more severe. Large branches or even the trunk can be girdled by the larval galleries. Studies have also shown that if the canopy of a tree is already declining when insecticide treatments are initiated, the condition of the tree may continue to deteriorate during the first year of treatment. In many cases, the tree canopy will begin to improve in the second year of treatment. This lag in the reversal of canopy decline probably reflects the time needed for the tree to repair its vascular system after the EAB infestation has been reduced. Scientists have learned that ash trees with low densities of EAB often have few or no exter- nal symptoms of infestation. Therefore, if your property is within a county that has been quarantined for EAB, your ash trees are prob- ably at risk. Similarly, if your trees are outside a quarantined county but are still within 10-15 miles of a known EAB infestation, they may be at risk. If your ash trees are more than 15 miles beyond this range, it is probably too early to begin insecticide treatments. Treatment programs that begin too early are a waste of money. Remember, however, that new EAB infestations have been discov- ered every year since 2002 and existing EAB populations will build and spread over time. Stay up to date with current EAB quaran- tine maps and related information at www. emeraldashborer.info. You can use the links in this Web site to access specific information for individual states. When an EAB infesta- tion is detected in a state or county for the first time, it will be added to these maps. Note, however, that once an area has been quarantined, EAB surveys generally stop, and further spread of EAB in that area will not be reflected on future maps. -' 1 realllH lhat i \/\'ill ha.,/e to protect my ash tn:f:.g froilI EAB for sevPfi::d ye;FS. L:; it worth it? The economics of treating ash trees with insecticides for EAB protection are com- plicated. Factors that can be considered include the cost of the insecticide and expense of application, the size of the trees, the likelihood of success, and potential costs of removing and replacing the trees. Until recently, insecticide products had to be applied every year. A new product that is effective for two years or even longer (emamectin benzoate) has altered the eco- nomics of treating ash trees. As research pro- gresses, costs and methods of treating trees will continue to change and it will be impor- tant to stay up to date on treatment options. Benefits of treating trees can be more difficult to quantify than costs. Landscape trees typi- cally increase property values, provide shade and cooling, and contribute to the quality of life in a neighborhood. Many people are sen- timental about their trees. These intangible qualities are important and should be part of any decision to invest in an EAB management program. It is also worth noting that the size of EAB populations in a specific area will change over time. Populations initially build very slowly, but later increase rapidly as more trees become infested. As EAB populations reach their peak, many trees will decline and die within one or two years. As untreated ash trees in the area succumb, however, the local EAB population will decrease substantially. Scientists do not yet have enough experi- ence with EAB to know what will happen over time to trees that survive the initial wave of EAB. Ash seedlings and saplings are common in forests, woodlots, and right-of- ways, however, and it is unlikely that EAB will ever completely disappear from an area. That means that ash trees may always be at some risk of being attacked by EAB, but it seems reasonable to expect that treatment costs could eventually decrease as pest pressure declines after the EAB wave has passed. INSECTICIDE OPTIONS FOR PROTECTING ASH TREES FROM EMERALD ASH BORER