BROOKINGS – I received a text the morning of Saturday, May 6, from a Sioux Falls tree company that was pruning some ash on a client’s property. This was pruning for clearance away from the structure, not because the trees were declining or dying.
One of the crew members noticed woodpecker pecks in the branches pruned from the upper canopy of some of the green ash (Fraxinus pennsylvanica). The crew set these branches aside on the ground. The crew leader pulled the bark away and found galleries and during further investigation discovered a larva.
I arrived at the site about an hour later. The woodpecker pecks and blonding were not very extensive on these ash or the surrounding ash trees and were mostly concentrated in the upper canopy. Woodpecker pecks and blonding – where the woodpeckers have removed patches of bark in their search for the larvae – are excellent means of identifying an infested tree. Woodpeckers seem to have the ability to find the borer before we do!
The crew had left all the brush from the two ash they had pruned for me to inspect. The bark slips easily in the spring, so I was able to pull the bark back from the cambium in long sheets. The galleries beneath the bark were widely separated from one another and in very tight serpentines. These are indicators of a relatively recent infestation, perhaps only a couple of years, in otherwise healthy trees.
I removed larvae from the galleries. The larvae were 1/2- to 1-inch long, white, flattened, with 10 bell-shaped segments and a pair of brown pincher-like spines on the last segment. The majority were alive but about one-third were discolored and dead – they appear to have died during the winter. I was able to find several different larval instars but no pupa or adults. However, I did find a few D-shaped holes where adults emerged last year.
As is required, the larvae were sent off to be verified by the Animal and Plant Health Inspection Service in Washington, D.C., and we received the confirmation on Wednesday.
So far, we have identified about 250 infested trees in the north side of Sioux Falls. The infestation appears to be recent – perhaps 3 or 4 years old – and concentrated. This is good news, if finding emerald ash borer can be considered good news. Thanks to the great observation skills of a local tree company and our quick response the insect was identified early, and management of the infestation can begin.
So now what?
If you live within 15 miles of the northern part of Sioux Falls, you do not need to have anyone come out to inspect your ash trees. You can assume your tree will become infested soon – within 10 years – or may even already be infested. If you would like to keep the ash, treatments should begin this spring. There are several available treatment methods, but many opt for trunk injections. These need to be performed every two years but are highly effective in saving your tree if done properly. Regardless, the most effective means of treating for emerald ash borer is to contact a commercial applicator.
Within this area you should also avoid pruning ash until autumn as fresh pruning cuts will attract the beetles. You should also avoid removing an ash tree during the summer months as the beetles emerge during this time (within a few weeks from now) and the adults can fly out of infested logs.
There are quarantines being established for Minnehaha and some parts of the surrounding counties to the south. These will be announced soon and movement of any ash – tree, log, wood – cannot be out of these areas.
What if I live outside the Sioux Falls area?
The fact that emerald ash borer was confirmed in Sioux Falls does not mean it is found throughout the state or that it will quickly move to other communities. Quarantines will help slow the movement out of this area and it may be years or decades before a specific community is also impacted by the borer.
The best approach for other communities is inspecting ash trees for the most common symptoms of an infestation – woodpecker pecks and blonding – and report any suspicious trees. Do not assume if your ash is declining, it’s emerald ash borer. Most of the ash in South Dakota have some degree of dieback and many are already infested by our native borer. Dying ash are not unusual in our state.
The South Dakota Department of Agriculture and the South Dakota Cooperative Extension Service have information on their web sites to answer more questions on this insect.
John Ball photos/SDSU:
Above, emerald ash borer larvae found in green ash in northern Sioux Falls.
Below 1, an emerald ash borer adult.
Below 2, en emerald ash borer infested tree is shown with woodpecker pecks.
Below 3, emerald ash borer larva and galleries in an ash tree in Sioux Falls May 5.
Kenneth R. Law photo, USDA APHIS PPQ, Bugwood.org:
Below 4, an emerald ash borer D-shaped emergence hole.
