Emerald Ash Borer
Risk Maps

Over the past few years, we have analyzed the risk of emerald ash borer's introduction and spread in Wisconsin by specifying predictive factors associated with emerald ash borer infestation and spread, and incorporating them into a risk assessment model. Risk mapping involves determining the factors affecting the probability that an event, such as the introduction of emerald ash borer into Wisconsin, will occur. Each factor is assigned a weight; the weighted factors are added to determine the overall risk or probability of the event; and the results are mapped.

Risk Map: Emerald Ash Borer Introduction

Based upon observed patterns of emerald ash borer introductions in nearby states, four factors were used in the Wisconsin model:

1. Human population density: The major pathway of introduction will probably be transportation of emerald ash borer from infested areas by people.
2. Number of campsites in a county: Infested campfire wood is predicted to be a major vector of this wood-boring insect.
3. Basal area (or volume) of live ash.
4. Density of seasonal homes: Firewood may be transported from permanent homes in infested urban areas to vacation homes in un-infested woodlands.

The resulting map shows that major population areas and parts of northern Wisconsin where ash is abundant are at high risk for emerald ash borer introduction.

Risk Map: Emerald Ash Borer Spread

In order to predict the risk of spread once emerald ash borer has been introduced into Wisconsin, two factors were considered:

1. Risk of emerald ash borer introduction.
2. Basal area of live ash present.

Since ash trees are abundant in both urban centers and in the maple-basswood forests of northern Wisconsin, these areas are predicted to be the most highly affected by emerald ash borer populations.