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On May 14, 2009, emerald ash borer (EAB) was confirmed as present in the South Saint Anthony Park neighborhood in St. Paul. EAB is a serious invasive tree pest, and consequently a quarantine has been placed to help slow the spread of EAB to other areas.
EAB is an insect that attacks and kills ash trees. It is spread through transported firewood. The adults are small, iridescent green beetles that live outside of trees during the summer months. The larvae are grub or worm-like and live underneath the bark of ash trees. Trees are killed by the tunneling of the larvae under the tree's bark. Check out this video on the life cycle of EAB.
EAB is native to eastern Asia but was discovered in Detroit, Michigan, and Windsor, Ontario, in 2002. Indications are it may have been introduced to this area as early 1990. EAB has been spread in ash firewood, nursery stock and possibly other ash materials to a number of new areas. View map of EAB finds and quarantines in Minnesota by clicking the map icon to the right, or by clicking here. View the national quarantine map here.
EAB kills ash trees. All ash trees are susceptible to EAB and millions of ash trees have been killed in infested areas already. Minnesota has the highest volume of ash trees in the U.S. with almost a billion forestland and urban wood ash trees. The potential economic and environmental impacts of losing these trees is substantial. The cost of removing and replacing a single tree can range from hundreds to thousands of dollars – how many ash trees are in your yard? Here is a guide for Ash tree Identification (PDF: 7.95 MB / 2 pages).
Myth No. 1. We can’t do anything about EAB anyway; we might as well let it spread.
EAB is a devastating pest; our choices now for ash trees near an outbreak are either treat or remove. Slowing the actual spread of EAB may mean economic viability for cities that are affected. If nothing is done to slow the spread, EAB can kill all area ash trees in a very short time. Slowing the spread means a city can spend $1M a year on ash tree removal for eight years, instead of spending $8M in one year for all the dead trees. Spreading the costs over many years is easier on any city’s budget, and that city’s taxpayers. Another reason is to buy time to let the science catch up: detection methods are improving and more is being learned about EAB weaknesses. Additional research is needed, but it takes time. While it’s unlikely there will be a silver bullet, if scientists can find enough weaknesses in EAB, we may be able to save ash tree species in the U.S.
Myth No. 2. EAB has no impact on human health, it just kills trees.
EAB-killed trees dry out quickly and become hazard trees in less time than after a normal tree death. Hazard trees are trees that can be dangerous because of the possibility of them falling over or large branches breaking off, with a potential to cause personal injury to people. In addition, a recent study by the U.S. Forest Service found that the decrease in tree numbers due to EAB in the Detroit, Michigan area (where EAB started) caused an increase in human mortality related to cardiovascular and respiratory systems.
Minnesota Department of Agriculture considers May 1 – September 30 to be the flight season for emerald ash borer (EAB). This means that EAB adult beetles are emerging from infested wood or trees and flying in search of new hosts during this time. EAB larvae complete their development by pupating into adult beetles in the spring and early summer. However, this process only occurs when temperatures are sufficiently warm and the whole process requires a certain amount of accumulated heat – i.e., development time. Accumulated heat can be measured and tracked by using degree days which are a measure of time spent above a threshold temperature.
For EAB a base temperature of 50° F is used and the following are estimated thresholds for EAB activity:
450 degree days – first EAB adults may begin emerging
900-1100 degree days – peak EAB adult activity
Current base 50° F degree day accumulations for Minnesota and Wisconsin are available from UW Extension Ag Weather.
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Helpful External Links
Minnesota Department of Agriculture (MDA), 625 Robert Street N, St. Paul, MN 55155-2538, firstname.lastname@example.org