“Trees shade and cool our homes, bring songbirds close by, mark the changing seasons. Kids can climb them or build a tree house in their branches. For all of us, trees are a source of lumber, food, and countless products – and they beautify our communities and countryside. But equally important, trees conserve energy, reduce soil erosion, clean the air we breathe, and help protect rivers and streams. If trees are to provide all these benefits, we need to care for the trees we have, and to plant more. As you plant and care for your trees, you can be sure that you are making the future better for your family, your neighborhood, your countryside, your world. ” – Arbor Day Foundation
The goal of the Dutch Elm Disease Program is to slow the spread of Dutch Elm Disease to a rate where the tree canopy stays the same, only with new tree replacements moving into the tree population at the same rate as losses. This can be seen throughout the older established neighborhoods in Grand Forks. The first case of Dutch Elm Disease in Grand Forks was discovered in 1979. From 1979 to 2020, the Forestry Department removed 9,200 diseased elms and due to their efforts around 3,000 are left on the berms and in the parks today. The Forestry Department also are working to plant new Dutch Elm Disease resistant species of elms throughout Grand Forks.
- Scouting for diseased elms, firewood piles and other sources of elm beetle nesting sites.
- Removal of confirmed diseased trees on berms, parks, private property and the city river corridor.
- Removal of confirmed diseased trees on private property is free to homeowners.
- General berm tree tree maintenance (pruning, removal, and planting) contributes extensively to the program.
Does your tree have Dutch Elm Disease?
During the months of June, July, and August, a Grand Forks Park District scout continually surveys all elm trees for signs of Dutch Elm Disease. The scouts inspect all elms on berms, parks, private property and the river corridor. The first evidence of the disease generally is wilting or flaggling in one or more of the upper branches. Leaves on affected branches turn dull green to yellow and curl, then become dry and brittle, and turn brown. Peeling bark from wilted branches reveals light to dark brown streaks. The scouts test the samples and if positive the trees are marked and a notice is left for the homeowner.
Emerald Ash Borer (EAB) is native to eastern Asia and it is believed that this beetle was unintentionally brought to the U.S. in infested ash crates or pallets. The most recent findings have been in Winnipeg, Manitoba in 2017, Sioux Falls, South Dakota in 2018 and Sauk Centre, Minnesota in 2019. EAB has already killed 100’s of millions ash trees within North America. Federal and state quarantines have been imposed that regulate the interstate movement of ash material from infested areas.
Description: Adult beetles are a half inch long and slender. The wing covers are rough metallic emerald green and the rest of the body appears metallic golden green.
Damage & Symptoms: EAB attacks and kills all ash species and cultivars regardless of the tree’s health or size. Larvae damage the conductive tissues and restrict the trees ability to move nutrients. The first visible symptoms are thinning and dieback of foliage. After dieback, trees often grow a large mass of shoots below the infested area. Close inspection may reveal “D” shaped exit holes, vertical splits in the bark over the infested area, and serpentine tunnels under the bark.
EAB & North Dakota: At this time, no evidence of EAB has been detected in North Dakota or Grand Forks. EAB can move only short distances on its own, but when transported by way of infected ash materials, the beetles can move from one state to another in a matter of hours. Annually, the Grand Forks Park District Forestry Department works with the ND Department of Agriculture in setting EAB traps throughout Grand Forks. The traps are inspected throughout the season to detect any signs of EAB.
What can you do? When camping, leave your firewood at home and purchase local campsite firewood. Only purchase what you will use. Burn all wood and do not travel with wood. When at home, only purchase from local firewood sources and burn wood within the season. Diversify your tree plantings (do not put all your eggs in one basket).
Recommended Tree Species: Linden Cultivars, Crab Cultivars, Emerald Luster Maple, Unity Sugar Maple, Ohio Buckeye, Black Walnut, Hackberry, Northern Acclaim Honeylocust, Bur Oak, Japanese Tree Lilac, Prairie Expedition Elm, Cathedral Elm, Discovery Elm.
What are Carpenter Worms:
In Grand Forks there has been significant damage to our ash trees by carpenterworm. Carpenterworms are native to our region unlike insects such as Emerald Ash Borer (EAB) which found its way to the United States from Asia in 2002. (As of 3/8/23 the closest location to Grand Forks EAB has been found is Moorhead, MN. Currently EAB has been confirmed in 36 states across the country and in Winnipeg, MB).
During early summer, the female carpenterworm moth deposits her eggs in cracks or crevices in damaged areas of trees. When the young larva hatches, it feeds on the sapwood of the tree. After the larva matures, it bores into the heartwood of the tree. The larva lives in the tree for 3-4 years and can get as large as 2-3 inches long at maturity. At the end of its life cycle, the carpenterworm exits the tree as a moth. Signs of carpenterworm are large holes around ½ inch in diameter on the trunk or branches along with frass (sawdust) near the holes. Holes can be further enlarged by Woodpeckers which feed on carpenterworms.
One thing that has made matters worse is the variety of ash trees planted. Pyramidal ash trees have a growth habit that forms a tight “V” union in the center of the tree. This union can form a small crack (referred to as included bark) in the central leader of the tree. Other common damage found in pyramidal ash are frost cracks, which are caused by fluctuating temperatures in the wintertime. The reason this is significant is the fact that carpenterworm moths deposit their eggs in cracks or damaged areas of the tree.
Carpenterworm have found a great location to live and spread, in streets were we have monoculture of pyramidal ash trees.
How are Carpenter Worms Killing Our Trees:
Carpenterworm causes damage to the sapwood and heartwood layers in tree during its life cycle of 3-4 years. Small infestations are less of an issue but when the population of the insect is larger (as we see in Grand Forks) it can cause enough damage to the tree that the health of the tree begins to decline. Eventually it will kill most of the tree. Adding to damage caused by carpenterworms, woodpeckers feed on carpenterworm larva by enlarging the hole created by the carpenterworm to feed. This does help reduce the carpenterworm population but it also causes more damage to a tree that is already stressed and declining.
The accumulation of damage from carpenterworms, woodpeckers, and other insects also introduce wood decay organisms.
Carpenterworms + Woodpeckers + Wood Decay = Tree Decline
Once the tree reaches the point where over half the tree is dead, removal is recommended so the tree does not become a hazard.).
What Controls Can be Used for Carpenter Worms:
Because carpenterworm larvae live deep inside the tree and the moth flight period is long, targeting carpenterworms with insecticides is difficult. There are also options using mechanical and biological treatments. Unfortunately, both methods are too labor intensive for the Forestry Department to administer to the roughly 12k ash trees we manage. However these treatments are manageable for property owners that have just a few trees to treat.
Mechanical method (works best with small infestations):
- First identify the hole(s) created by the carpenterworm and look the for frass (sawdust) in and around the hole.
- Next remove the frass from inside and around the hole.
- After the frass has been removed, stick a long sharp wire in the hole to try and kill the larva. It might be hard to know if you were successful on the first try, so mark the hole(s) with some paint for future treatments.
- Check the hole(s) weekly to look for new frass around the hole(s), if you do see new frass, repeat the process over again until no new frass is found.
Biological method (always read and follow all label instructions before application):
- Treatments with beneficial nematodes Steinernema carpocapsae have been successful in controlling carpenterworm. Applications should be made in the spring or fall when the larvae are actively feeding.
- Clean the frass out of the gallery entrances.
- Mix the nematodes with distilled water into an applicator that has a long narrow nozzle and insert as far as possible into the galleries and inject the liquid.
- Plug the entrances with rope putty or grafting wax to seal the holes.
- A second application may be necessary in 1-2 weeks if there are new signs of carpenterworm activity.
How are we going to lose all our Ash Trees?
Our ash trees are being attacked by carpenterworm, but they are primarily attacking our pyramidal ash trees for reasons stated above. Although we do find carpenterworm in our broad growth habit ash trees, we aren’t in danger of losing large numbers of these trees to carpenterworm. Carpenterworms also attack other types of trees such as aspen, elm, birch, oak, and poplar trees but they typically won’t kill these trees in large numbers. The main threat is to our pyramidal ash trees.
Emerald Ash Borer (EAB) is a far greater threat to our ash population (and only our ash trees) when it finds its way to Grand Forks. Currently we have avoided EAB, but it has been found in 36 states since it was first discovered in Michigan in 2002, and with the discovery of EAB in Moorhead, MN in 2023 it will make its way to Grand Forks. The question now is when, not if, EAB will be found in Grand Forks. Currently there are treatments that can be used to save ash trees from EAB, but the treatment will only last for 2-3 years before it must be repeated. EAB treatments while effective, are very difficult and expensive to administer on a large scale for the roughly 12k ash trees the Park District maintains. Unless new treatments methods are developed, we will lose all non-treated ash trees in Grand Forks. The North Dakota Department of Agriculture doesn’t recommend treating ash trees until it’s been detected within 15 miles of your location.
Many EAB discoveries are found to have originated from firewood piles that were transported to the city from other areas. The insect itself doesn’t travel vast distances in a year but the insect overwinters inside the tree’s branches and trunk and will emerge in the Spring to look for new ash trees to infest. Our best defense against EAB is to not transport ash firewood into Grand Forks. It is recommended to burn or leave ash firewood where it originated and not transport it to new areas.