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You are here: NRS Home / Research Programs / Forest Disturbance Processes / Invasive Species / Emerald Ash Borer /Control and Management / Evaluation of Chipping and Heat Treatment to Control Emerald Ash Borer
Emerald Ash Borer

Evaluation of Chipping and Heat Treatment to Control Emerald Ash Borer

Research Issue

[photo:] Researchers collect bins of chipe to study effects of chipping and heat treatments on eab.The emerald ash borer (eab), a phloem-feeding insect from Asia, was identified in 2002 as the cause of widespread ash mortality in southeast Michigan and Ontario.  Most larvae overwinter as non-feeding prepupae in the outer sapwood or thick bark of large trees.  Mechanical destruction of infested trees with grinders or chippers has previously been used as a regulatory treatment for wood infested by wood-boring or phloem feeding-insects.  However, effectiveness of grinding or chipping infested ash material has not been previously evaluated for eab, particularly in winter and early spring when most of the insects are prepupal larvae.  During this stage, the larvae are folded into oval cells within the sapwood or thick bark, where they may be somewhat protected from desiccation or injury during processing.  Moreover, prepupal larvae require no additional feeding and uninjured individuals could potentially complete development without intact host material.  In contrast, larvae that are still feeding in ash phloem between the outer bark and sapwood are more vulnerable to exposure, injury and desiccation resulting from bark separation during grinding or chipping. 

 Our Research

In a series of studies, we evaluated effects of grinding, chipping and heat treatment on survival of eab prepupae in ash material.  Heavily infested ash bolts containing roughly 8700 prepupae were processed by a horizontal grinder with either a 2.5 or 10 cm screen.  We chiseled additional sentinel chips with prepupae from ash logs and buried 45 in chip piles constructed from the chips created by the grinder.  Subsequently, we assessed prepupal survival in chips processed by a chipper or a horizontal grinder fit with 5-, 10, or 12.7-cm screens.  Infested wood and bark chips chiseled from logs were held in ovens at various temperatures from 25 to 60 °C for different periods of time from 20 min to 48 h. 

Expected Outcomes

Evaluation of regulatory treatments including chipping and heat treatment will lead to recommendations for regulations on treating eab infested material.  The results demonstrate that chipping with a chipper or with a grinder fit with a small screen (2.5 cm) results in smaller chips and is more effective in destroying eab.  Heat treatment at 60°C for at least 120 min is required to kill eab in bark or wood chips.

Research Results

There was no evidence of eab survival in chips processed by the grinder with the 2.5 cm screen but eight viable prepupae were recovered from chips processed with the 10 cm screen.  A total of six prepupae in sentinel chips survived the winter but we found no evidence of adult eabemergence from the piles of chips processed by the grinder with either the 2.5 cm or 10 cm screenIn the subsequent experiment with the chipper and grinder fit with 5-, 10-, or 12.7-cm screens, an estimated 1565 eab prepupae were processed in the logs by each treatment.  Chips from the chipper were shorter than chips from the grinder regardless of the screen size used.  No live prepupae were found in chips produced by the chipper but 21 viable prepupae were found in chips from the grinder. Prepupal survival was consistently higher in wood chips than bark chips held at 40 °C, while no prepupae survived exposure to 60 °C for 8 or more h.  Some prepupae survived 20 min of exposure to all temperatures.  No prepupae survived exposure to 60 °C for 120 min but 17% survived exposure to 55 °C for 120 min.


Research Participants

Principal Investigators

  • Deborah McCullough, Michigan State University
  • Therese Poland, USDA Forest Service - Northern Research Station Research Entomologist

Research Partners

  • David Cappaert, Michigan State University
  • Ivich Fraser, APHIS
  • Vic Mastro APHIS

Last Modified: 12/07/2017

About this Research Area
About Emerald Ash Borer
Selected Studies