Wood Management/Utilization
Biological Control


A mission of the Minnesota Department of Agriculture (MDA) is to prevent the movement of invasive plant pests into areas of the state that are not yet infested. This document provides communities and other entities responsible for ash trees in landscaped areas with guidelines to slow the spread of emerald ash borer to areas of Minnesota that are not yet infested. While communities and others following these guidelines may derive additional benefits, such as a reduced rate of ash mortality, this document was written from the perspective of protecting for as long as possible the areas of the state where emerald ash borer does not yet exist. As such, other planning documents should also be consulted and used in developing a comprehensive community emerald ash borer management strategy.



EAB 101

Emerald ash borer (EAB), Agrilus planipennis, is an invasive wood-boring beetle first detected in the U.S. near Detroit, Michigan in 2002. Since that time, EAB has killed millions of ash trees. All ash trees native to Minnesota are considered highly susceptible to EAB. Minnesota has about one billion ash trees in our forests, and ash accounts for about 15 percent of trees in the average community (Minnesota Department of Natural Resources, 2010).

A single generation of EAB is completed in one to two years. Eggs are laid during the summer on trunks and branches of ash trees. Larvae hatch from the eggs and tunnel beneath the bark. Larvae make distinct “S”-shaped (serpentine) galleries and feed on the phloem of the tree. Larvae may spend the winter inside pupal chambers in the outer sapwood, bark, or in feeding galleries, and some larvae will feed for another summer before completing development. Adults emerge from ash trees through a distinct “D”-shaped exit hole from May through September. Upon emergence, adults will feed on ash leaves in the canopy before mating and laying eggs.

Trees are killed by continual larval feeding, and tree mortality accelerates as EAB populations increase in density. Although the beetle is capable of spreading to nearby areas through flight, the primary means of long distance EAB spread to new areas is through the transport of firewood or other woody material from ash trees.


The best strategies for slowing the growth and spread of EAB depend on the level of infestation. We define here three broad categories of infestation, each of which would warrant different types and levels of management. These categories should not be considered exclusive, but rather a spectrum.

  • Not Known To Be Infested – these are areas where EAB has not yet been found. EAB will be present in an area for several years before being detected. However, until detection has been made, areas where EAB has not been found are best considered not infested. As of January 2018, most of Minnesota falls into this category.
  • Generally Infested – EAB infested trees have been found, but trees are not yet being killed by the insect. As of January 2018, this includes a large area of southeastern Minnesota through the Twin Cities metro, a portion of Duluth, and a portion of Martin County.
  • Heavily Infested – trees killed by EAB are present. In this stage, the EAB population is sufficiently large enough to kill trees faster than they can be removed. As of January 2018, this includes the core area of the Twin Cities (mainly Minneapolis and St Paul) and a larger area in southeast Minnesota.



It is important to understand the goals of any particular management work before it is implemented. A very general but important distinction is the difference between activities that only impact the tree canopy versus those that also impact EAB populations. The difference between the two is simple:

EAB management tactics directly reduce the population size of EAB, tree canopy management tactics do not.

For instance, the removal of ash trees not infested with EAB would be considered a tree canopy management tactic because it has no direct impact on the EAB population. The removal (and destruction) of EAB infested ash trees would be considered an EAB management tactic because it directly reduces the EAB population. In every forest there is a need for tree canopy management; where EAB is present, there is the additional opportunity for EAB management.


EAB in natural forests is difficult to manage because the trees are generally less accessible, more numerous, and of lower value on a per tree basis than trees in community or landscaped areas. As a result, the only practical EAB management tool for natural forests at this time is biological control. Consequently, management in natural forests primarily needs to focus on tactics for managing the tree canopy and not EAB – even in areas where EAB is present. “Ash Management Guidelines for Private Forest Landowners” as well as other resources are available from the University of Minnesota.

In landscaped areas such as communities and other residential areas, there are greater potential benefits from implementing EAB management tactics. These areas are also likely to be the first places where EAB appears and also the easiest places from which EAB spreads. Thus, the potential benefits from EAB management tactics in communities and other residential areas is much greater than in forested areas.