Optimizing tree injections against emerald ash borer

Background

The emerald ash borer (EAB) was discovered in Minnesota trees in 2009, and infestations have since been confirmed in 13 of 87 counties. This insect poses unique challenges to city governments who made ash trees a fixture in their urban infrastructure plans years ago. These trees have helped reduce air pollution, storm water runoff and cooling costs while increasing property values in local communities.

Today’s recommended treatment for an EAB-infested ash tree is injection of insecticide into the trunk. We also think that by treating enough trees in a local population with injection, it may be possible to achieve “herd immunity” against EAB. Herd immunity refers to the phenomenon through which treating a certain portion of a population confers protection to untreated members as well.

This project will focus on optimizing the protocol for treatment of Minnesota’s urban ash trees to protect as many trees as possible. Researchers will determine what percentage of trees must be treated to achieve EAB herd immunity, and assess the possible effects of treatment on bees and other local pollinators.

The information learned will inform local governments’ plans for safely and effectively protecting their ash on a citywide scale.

Research questions

• What proportion of trees must be treated to achieve herd immunity against EAB?
  
  
• Does a thorough biological survey suggest any danger of the treatments to non-target insects like bees and other pollinators, either through ingestion of plant material or contact with foliage?
  
  

Practical implications

This work will guide cities towards an ideal EAB management strategy, considering insect density, forest management goals and environmental safety. As EAB continues to spread to new urban areas across the state, cities will be looking towards this information to help reduce cost and maximize results.

Details

Funding:

$320,000

Collaborators:

Minnesota Department of Agriculture

Research Team:

Brian Aukema, principal investigator

Dorah Mwangola, PhD student