Evaluation of Xylem Discoloration in Ash Trees Associated with Macroinjections of a Systemic Insecticide

Abstract

Emerald ash borer (EAB) (Agrilus planipennis), first identified near Detroit, Michigan, U.S., in 2002, has killed millions of ash trees (Fraxinus spp.) in 28 states and two Canadian provinces to date. Trunk injections of insecticide products containing emamectin benzoate (EB) (e.g., TREE-ageR) are often used to protect ash trees in landscapes from EAB, but wounds and potential injury resulting from injections are a concern. Researchers examined 507 injection sites on 61 trees and recorded evidence of secondary wounding (e.g., external bark cracks, internal xylem necrosis and pathogen infection). Researchers assessed 233 injection sites on 22 green ash and 24 white ash trees macro-injected with a low or a medium-high rate of EB in 2008 only, or in both 2008 and 2009. Only 12 of 233 injection sites (5%) were associated with external bark cracks and there was no evidence of pathogen infection. On 39 of the 46 trees (85%), new xylem was growing over injection sites. Researchers assessed 274 injection sites on 15 green ash trees injected annually with EB from 2008 to 2013 or injected in 2008 and again in 2011. Bark cracks were associated with four injection sites on three trees, but no evidence of injury was found on the other 12 trees. All 15 trees had new xylem laid over injection sites. Confocal laser scanning and polarizing digital microscopy were used to assess the integrity of discolored xylem tissue removed from the immediate area surrounding 140 injection sites on 61 trees. Researchers found no evidence of decay associated with discoloration.

Biological invasion threatens keystone species indelibly entwined with Indigenous cultures

“…Methods for freezing or drying partially processed splints that can be rehydrated also warrant consideration. Ongoing discussions among basketmakers include potentially using alternative materials to sustain traditional basketry practices such as Manchurian ash ( Fraxinus mandshurica ), an Asian species related to black ash but more resistant to EAB infestation (Tanis and McCullough 2016). Members of several Tribal Nations have participated in national or local efforts to collect and store seed from black ash populations to conserve genetic diversity prior to EAB invasion.…”

Evaluation of Trunk Injection Techniques for Systemic Delivery of Huanglongbing Therapies in Citrus

“…The OTC formulation had a pH of 1.8 and the IMI formulation had a pH of 4.6, corresponding to more damage and discoloration caused by the former than the latter. However, the discoloration may also be, at least in part, associated with the color of the formulation (Tanis and McCullough 2016). Research on how the concentration and/or formulation of a specific crop protection material affects wound healing and compartmentalization as well as longer-term impact on tree health is necessary before using it on a larger scale.…”

Observation of External Wounding on Green Ash (Fraxinus pennsylvanica Marshall) Trees Associated with Tree Injection Systems

“…Bark cracking was observed in this study and was included as a part of overall wounding. Tanis and McCollough [24] observed 5% of green ash and white ash (Fraxinus americana L.) trees developed bark cracking in their field study in central Michigan, MI USA. Aćimović et al [14] found vertical bark cracking occurred the first season with every system they studied.…”

“…However, bark cracking or a canker may result from the wound associated with drilling and other factors as a part of tree injection. In two short-term studies with ash trees, after two years less than 5% of trees showed external bark cracking [23,24].…”