May 26, 2016
Emerald Ash Borer and Camels
In my 38-year Extension career, I never remember talking so long about a pest that wasn't even here! I'm sure part of the reason is that emerald ash borers (EAB) are so devastating to ash trees. Since its arrival, EAB has killed hundreds of millions of ash trees.
EAB was first discovered in the United States in 2002 near Detroit in southeastern Michigan. I attended a conference in Michigan in the summer of 2007 and saw the devastation first hand. By then, EAB had spread through most of Michigan's lower peninsula as well as into the upper peninsula, Ontario (Canada), neighboring states, and to an isolated outbreak in Maryland. The Maryland area was over 300 miles away from the closest confirmed case of EAB at that time.
The Maryland outbreak is significant because it shows how EAB can move over long distances. On its own, the adult EAB is not a strong flyer, according to the USDA Forest Service, and most will move less than two miles a year. (About 1% of the mated females may disperse up to 12 miles.) With help from humans, however, it is a great traveler. It has been known to travel large distances, migrating in firewood or nursery stock from infected areas.
Currently, the closest confirmed infestation to Nebraska is in Union County, Iowa, about 80 miles east of Plattsmouth on Highway 34. Other infestations have been confirmed in the Kansas City area as well as in Boulder, Colorado.
Our current recommendation is to not start treating for EAB until its presence has been confirmed within a 15-mile radius of your ash trees. Thus, at this time, we would not recommend treating any ash tree in Nebraska for EAB.
I'm sure many of you thought I'd completely lost my mind (and you might have a point) when you saw a reference to camels in this column's title. Let me explain.
Last summer I was visiting with an older gentleman who lived near Pierce. When he found out what I did for a living he was quick to ask what I knew about emerald ash borer. I explained that it will almost certainly get here - someday, but I would not recommend treating for this pest until it has been confirmed within 15 miles of his home.
He told me he recently went to a large chain nursery and asked them about EAB. They told him he needed to start treating his ash trees immediately and sold him a treatment costing several hundred dollars.
I asked him if he knew that same product would be 100% effective on preventing camel damage to his ash trees. He glared at me and snapped back that he wasn't worried about camel damage, he didn't have any camels. Before I could respond, his glare turned to a big grin and all he said was, "I get it!" He also mentioned that he would be returning any unused product. When I counted my many blessings that night, I included that I would NOT be the person at the nursery accepting the product he returned.
EAB adults are small, metallic green beetles. They are about 1/2 inch long and 1/16 inch wide. Several other green insects are easy to mistake for EAB, but you can distinguish EAB based on body shape. If you look at EABs from above, their body is shaped like the head of an ax, blunt and flat across the head and tapered toward the tail. One other unique characteristic is that when their wings are spread like they are flying, the top of their body which is normally hidden by their wings is reddish in color.
Adult EABs emerge in late May to late June, leaving a "D-shaped" hole in the trunk. Females lay eggs about two weeks after they emerge and these eggs hatch in one to two weeks. The tiny larvae bore through the bark and into the cambium, the area between the bark and the wood, where nutrient levels are high.
EAB larvae injure ash trees by feeding under the bark where they damage the conductive tissue or "plumbing" of the tree, disrupting the flow of moisture and nutrients. The larvae eventually form a pupa and the new generation of adults emerge the following May or June to begin the cycle again.
Understandably, homeowners are concerned about losing their ash trees to the EAB. However, it is important to not begin insecticide treatment too early as premature treatments can have negative consequences. Some treatment involve drilling holes around the trunk through the bark and into the cambium to inject a systemic insecticide. Research has shown that healthy trees can be injected seven to 10 times before trunks become so damaged that trees begin to decline.
The drilled holes also open the trunk to insect pests and decay fungi. Drilling may break through the internal barriers in the trunk the tree is using to wall off internal decay, causing decay to spread. Also, the insecticide itself can cause internal damage. This is why treating ash trees for EAB is not, and will not, be recommended for trees until it has been found within 15 miles of a tree's location... or if you are concerned your ash trees might be overrun by camels.
For more information including images to help identify this pest and the damage it causes, visit the Emerald Ash Borer Information Network at http://www.emeraldashborer.