Federal identification has confirmed the presence of the emerald ash borer (EAB) in Plymouth County for the first time. Insect samples were collected by the Iowa Department of Agriculture and Land Stewardship from an ash tree in Remsen after an area tree service alerted the department of a tree with symptoms of an infestation. EAB is a non-native, wood-boring insect threatening all species of ash trees.
The adult beetle is approximately one-half inch long and metallic green. The larval stage of this insect tunnels through the wood just beneath the bark of ash trees, cutting off the tree’s ability to transport water and nutrients. The cumulative damage typically kills a tree within two to four years after becoming infested.
Indicators of an infestation may include canopy thinning, leafy sprouts shooting from the trunk or main branches, serpentine (“S”-shaped) galleries under the bark, bark splitting, woodpecker damage, and 1/8-inch D-shaped exit holes.
EAB was unknown to North America until its discovery in southeast Michigan in 2002. The invasive, ash tree-killing insect from Asia has now been found in 36 states and confirmed in all but two of Iowa’s 99 counties. The only remaining counties in Iowa without a detection are Emmet and Palo Alto. In 2010, EAB was first discovered in Iowa in Allamakee County.
Now is the time to decide a course of action for ash trees at risk of EAB attack (within 15 miles of a known infestation). Landowners and managers can wait and see what happens, remove declining ash trees and replace them with other species, or use preventive insecticide treatments to preserve and protect valuable and healthy ash trees. The best time to treat for EAB is in the spring, from mid-April to mid-May. Insecticides are most effective when the ash tree is actively growing and uptake is at its peak. Tree service companies can apply insecticide trunk injections through the summer if soil moisture is available.
Iowa State University Extension and Outreach has produced a publication about EAB treatments. For more information, download Emerald Ash Borer Management Options.
Source: iowaagriculture.gov
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