New Invasive Insect Confirmed in Iowa

By Erin Hodgson, Department of Entomology

The Iowa Emerald Ash Borer Team confirmed the presence of emerald ash borer (EAB) in Iowa on May 14. Four EAB larvae were found in one ash tree along the Mississippi River just two miles south of the Minnesota border in Allamakee County. The infested area is owned and managed by the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service. The Iowa EAB Team is made up of members from the Iowa Department of Agriculture and Land Stewardship, USDA Animal Plant Health Inspections, USDA Forest Service, and Iowa State University Extension. The team has been scouting for EAB since 2003 using several detection methods.

Description 
Larvae are creamy white with a brown head and are legless. They have flattened, bell-shaped body segments (Fig. 1). Adults have metallic green forewings and copper red abdomens, and are approximately three- to five-eighths inch long (Fig. 2). Adults emerge from May to August and leave distinctive "D" shaped exit holes in the outer bark of branches and trunk (Fig. 3). Many other wood-boring beetles can be confused with EAB (e.g., bronze birch borer, two-lined chestnut borer, white-spotted pine sawyer, cottonwood borer). It is important to distinguish native wood boring beetles from EAB. Adults can be sent to ISU for positive identification.

Figure 1

Figure 2

Figure 3

Why care about EAB?
The first EAB confirmed in the U.S. was in southeastern Michigan in 2002. Larvae kill North American ash species, including green, white, black and blue ash. Larvae feed on phloem just below the bark and create serpentine tunnels, or galleries, that eventually kill trees (Fig. 4). Adults will feed on leaves and create notches on leaf edges.
Several symptoms occur in EAB-infested ash trees.
• Vertical fissure on bark
• Serpentine galleries exposed if bark removed
• Galleries are filled with sawdust-like frass (excrement)
• Increased woodpecker activity
• Canopy dieback begins in top third of tree (Fig. 5)
• Shoots form at the base of the tree

Figure 4

Figure 5

Learn more about EAB
EAB main site     
Ash tree identification guide    

Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at ewh@iastate.edu or phone (515) 294-2847.