Reported Emerald Ash Borer Locations as of February 2011.
Above image from www.emeraldashborer.info
Above image from www.emeraldashborer.info
(Wang et al. 2010)
Larval gallery and new methods of detection
Serpentine galleries are created by the larval instars of A. planipennis. This occurs when the larvae consumes the phloem and cambium as it develops. This damage occurs out of sight and usually once it is detected it is too late to save the tree. However, new methods have been developed that are allowing for the detection of low density A. planipennis larva using a two branch testing method. The two branch testing method is 18 times more likely to detect the presence of low density EAB than the previoius trunk window testing method. The trunk window testing method resulted in a 81 percent false negative rate in a study by the Canadian Forest Service. These new methods are much more cost effective in the determination of EAB presence, and are much more efficient than felling entire ash trees. (Ryall et al. 2011)
Effect on Ash trees
The Emerald Ash Borer will attack a wide range of different species of the genus Fraxinus. This genus, which contains between 45-65 species, is susceptible to A. planipennis from May to late August. The death of ash trees occurs through the serpentine galleries created in the phloem and cambium by the larvae of A. planipennis. The larvae are the source of the majority of the damage done to the trees, while the adults primarily feed on foliage. These serpentine galleries reduce and even eliminate the flow of nutrients vertically in the tree. This lack of flow essentially kills the trees and results in the loss of canopy foliage and necrosis of affected areas above the serpentine galleries. (Hill et al. 2012)
A. planipennis has a few interesting habits. First of all, it is attracted to girdled ash trees. Trees that have been girdled, where they have been trimmed or have had bark removed, are highly stressed and thus are more attractive to the Emerald Ash Borer. Often trees are girdled intentionally by removing a ring or section of bark and phloem and used as traps for the adult Emerald Ash Borers. The EABs lay their eggs on the stressed ash tree, and then the stressed tree is felled later and inspected for larvae. (McCullough et al. 2009)
A. planipennis has a few interesting habits. First of all, it is attracted to girdled ash trees. Trees that have been girdled, where they have been trimmed or have had bark removed, are highly stressed and thus are more attractive to the Emerald Ash Borer. Often trees are girdled intentionally by removing a ring or section of bark and phloem and used as traps for the adult Emerald Ash Borers. The EABs lay their eggs on the stressed ash tree, and then the stressed tree is felled later and inspected for larvae. (McCullough et al. 2009)
There are several different signs of Emerald Ash Borer activity. Some visual signs of A. planipennis, according to the United States Department of Agriculture, include:
- 1. Canopy stress and dieback
- 2. Epicormic shoots and suckering
- 3. Bark split with larval gallery underneath
- 4. Woodpecker damage and excessive activity
- 5. D-shaped exit holes
- 6. Serpentine larval galleries
(USDA-APHIS 2011)