Archives For Tom Tiddens

Emerald Ash Borer: Sad But True, Part 3

The invasive insect appears to have spread to a different host.

Tom Tiddens —  October 23, 2014 — Leave a comment

Last week, a college biology professor in Ohio announced he had found evidence that the emerald ash borer (EAB), an invasive insect decimating the continent’s ash trees, is also attacking white fringetrees (Chionanthus virginicus).

PHOTO: White fringetree in bloom.

White fringetree (Chionanthus virginicus) in bloom

In August he found the telltale D-shaped exit holes on a fringetree near his home. When he investigated further by peeling back the bark, he found feeding galleries and live borers. He had the borers positively identified morphologically as well as with DNA tests conducted by the USDA’s Animal and Plant Health Inspection Service (APHIS). He also found evidence of EAB activity on fringetrees in three other locations in Ohio.

The recent discovery marks the first time EAB has been found completing its life cycle on anything other than ash in the United States.

The finding adds an alarming new element to the EAB story:

  • Researchers have been wondering whether the host range for EAB could be wider than just ash. That theory had seemed unlikely up to now but is proven with the fringetree discovery. There has already been a lot of research investigating other possible hosts, and with the new discovery, there will likely to be more.
  • Is the insect adapting? This is a scary thought!
  • Will EAB kill fringetrees as it does ash, or just cause damage? So far the invasive insect appears to only be damaging—not killing—fringetrees.
  • Has EAB moved to fringetrees because EAB populations are locally so high? If the buffet is crowded at the “prime rib station,” it seems logical that “meatloaf station” may get some visits.
  • What will happen when ash tree populations dwindle? Will the EAB population die back, or just move to a secondary host (the meatloaf, as the prime rib is gone) and/or develop a completely new palate?
PHOTO: A D-shaped exit hole left by EAB.

This D-shaped exit hole was left by a mature emerald ash borer as it exited this host tree.

The Ohio professor’s find was not all by luck; he had reason to focus on the white fringetree. Laboratory studies have shown that the adult EAB will feed on the foliage of other tree species in the same family as ash—the olive family, or Oleaceae. Members include ash (Fraxinus), fringe tree (Chionanthus), lilac (Syringa), forsythia, privet (Ligustrum) and swamp privet (Forestiera). Literature from Asia, the homeland of the EAB, indicates other secondary EAB hosts.

The Chicago Botanic Garden has 42 fringetrees; all have been inspected and show no signs of EAB activity. Even a fringetree that is 25 feet from an ash tree that was heavily infested with EAB shows no signs. If you have a fringetree, you should inspect it for signs of EAB. These include dieback starting at the upper limbs of the tree, new growth on the lower trunk, and small, D-shaped holes where the larvae have exited through the bark. Emerald ash borer larvae can kill a mature ash tree in two to three years by destroying the tree’s vascular system.

Find more information on identifying and dealing with EAB on our website, and in our previous posts, Signs of Emerald Ash Borer, and Emerald Ash Borer: Sad But True, Part 2.

As the world has become less fragmented by ease of transportation, more exotic, high-consequence plant pests and pathogens like EAB have entered—and will continue to enter—the country. Other exotic plant pests and pathogens we are watching for at the Garden include the following: viburnum leaf beetle, Asian gypsy moth, brown marmorated stink bug, Asian longhorned beetle, thousand cankers disease, plum pox virus, chrysanthemum white rust, sudden oak death, and so on; most are already in the country. Vigilance and education are the key to managing and slowing the spread of these foreign invaders.

The Garden is a member of the Sentinel Plant Network, a group that unites botanic gardens in monitoring and providing education on exotic plant pests and pathogens, and works in partnership with the National Plant Diagnostic Network (NPDN).

If you are a plant and bug person like me, please consider becoming a NPDN First Detector and help be on the lookout for these exotic plant pests and pathogens. The NPDN offers an online training course to become a First Detector at firstdetector.org. It’s free, and upon completion, you even get a printable certificate!

©2014 Chicago Botanic Garden and my.chicagobotanic.org

A couple years ago, in early spring, I got the kind of call that puts a “plant doctor” like me on edge. “Come look at the roses right away,” someone said. In my 25 years at the Chicago Botanic Garden, no one has ever called me to say, “Hey, Tom, come look at the roses; they look great today!” I’m in charge of plant healthcare at the Garden, so when I pick up the phone, there’s usually a problem.

I got the call about the Krasberg Rose Garden following a string of very damp nights that meant trouble—a white fuzz had spread over all the roses. The fuzz was a destructive pathogen that produces mycelium, or fungal spores. It can happen pretty much overnight. We ended up managing the problem, but it was scary to start off a season like that. Roses are tricky, prone to a lot of diseases and insect problems. Our friends at the Missouri Botanical Garden lost all their roses to a virus called rose rosette disease. 

I don’t just get calls about diseases or pests such as the emerald ash borer. I get called to the Butterflies & Blooms exhibition if the staff is worried about a larva or to the Elizabeth Hubert Malott Japanese Garden if there’s a raccoon problem. I like to say that I’m sort of like a CSI detective when it comes to plants. If a plant is failing, I try to find out why and what it needs. I look at the buds, the stem, the trunk, the root flare, the soil, and the plant’s history over the years.

PHOTO: Tom Tiddens poses with a cardboard coyote cutout, used to deter varmints from veg.

Tom Tiddens and a plant healthcare specialist’s best friend head out to play fetch.

I also work with the horticulturists on preventive care, including watering, pruning, weeding, and fertilizing. When I see a problem in the early stages, I’m very patient and tolerant. I like to see if Mother Nature might take care of it—maybe a hard rain will wash away any aphids or the ladybugs will get rid of the pests, for instance.

People ask me how I track the health of more than 2.6 million plants here. I have two great plant healthcare specialists who work with me, and I really rely on the horticulturists—they’re my eyes out in the field—and my volunteer team, which includes a lot of master gardeners. Every week, I give the volunteers a map and checklist marked with target plants and pests. So a typical volunteer assignment, for example, would be to check the spirea bushes in the Sensory Garden for aphids.

PHOTO: Bagworms infect a pine.

From bagworms…

PHOTO: Rust infects a fruit and leaf.

…to rust…



PHOTO: Black spot infects rose foliage.

…to black spot on roses, Tom Tiddens treats them all.

The average home gardener doesn’t have to be so methodical. Gardening shouldn’t be a chore. I like to keep things simple at home. I don’t like weeding, and I avoid using a lot of perennials or groundcovers. I like having a nice woodchip mulch bed and a mulching lawnmower. It’s the same thing with fall leaves. Everyone bags up all the leaves. Nope. I raise my mulching lawnmower, and I just grind them into the lawn.

Register now for a certificate class with Tom Tiddens, plant health care supervisor and certified arborist. From July 21 to August 28, he will teach Plant Health 2 with Kathie Hayden, the Garden’s manager of plant information service.    

©2014 Chicago Botanic Garden and my.chicagobotanic.org

Emerald Ash Borer: Sad But True, Part 2

The invasive insect appears to have weathered the polar vortex just fine.

Tom Tiddens —  April 24, 2014 — 2 Comments

In the past few months, the number one question I have been asked is “Will the cold winter have an effect on the emerald ash borer?” It’s sad but true that our cold winter will have very little effect on the emerald ash borer.

PHOTO: Emerald ash borer larva closeup.

An emerald ash borer larva lurks just under the bark of one of the Garden’s ash trees.

As we know, the emerald ash borer overwinters as larva under the bark, and that alone gives it some winter protection. More importantly, the emerald ash borer has another very interesting overwintering strategy: “supercooling.” In the fall, as the borer senses the cooler temperatures, it begins to produce a natural antifreeze that allows it to survive well below 32 degrees without freezing. The borer can also purge its stomach of materials that could freeze, flattening out and folding over. They are often found in this folded-in position under the bark in spring—I have seen this firsthand when I scraped the bark off an ash in January. Researchers in Minnesota have determined that it takes a prolonged period of about minus 25 degrees Fahrenheit or more to kill the borer. Our lows this past winter only reached about minus 16 degrees Fahrenheit (twice), as recorded by the Chicago Botanic Garden’s weather station. So, in our area, the march of the emerald ash borer continues undisturbed by our nasty winter.

PHOTO: A neighborhood ash tree with huge gaps in foliage, caused by dieoff from borer damage.

Crown die-off, due to emerald ash borer damage. Photo by Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org

If you have ash on your property, I recommend monitoring closely for signs of emerald ash borer; if you don’t see signs, it is only a matter of time. When you do discover the borer, begin treatments as soon as possible. Treatments are best made proactively—before you see signs of damage on the tree! You may wish to simply plan/budget to have your trees removed. Be aware that dead ash trees are hazardous, not just for their spread of the beetle. They become brittle quickly and become a hazard as limbs fail and fall.

The Garden is a great resource if you have questions or just want to learn more about the emerald ash borer. If you have recently removed ash trees, or have already scheduled removal and are looking for replacement trees, consider our list of ash tree alternatives. Drop by our Plant Information Service with your questions! Our new location is outside the Lenhardt Library.

Click here to register online for one of two informational sessions, Emerald Ash Borer: What You Need to Know, from 10 a.m. to noon on Friday, May 16, and Saturday, May 17. This is a free seminar, but advance registration is required.

©2014 Chicago Botanic Garden and my.chicagobotanic.org

Signs of Emerald Ash Borer

Tom Tiddens —  January 4, 2013 — 4 Comments

It’s sad but true:

As I drive around the north suburbs, I am noticing many roadside trees with a spray-painted mark or a ribbon around the trunk. As an arborist, I know that these are ash trees marked for removal because of the emerald ash borer (EAB). The emerald ash borer is beginning to hit our area hard, and many municipalities are trying to stay one step ahead of this ash-tree-killing insect by proactively removing these doomed ashes.  

woodpecker_damage_3If you have an ash tree on your property you should be monitoring for this pest, as it is only a matter of time before the borer finds your tree. In winter, the easiest way to identify if your tree already has EAB is to look for woodpecker damage. From a distance, woodpecker damage looks like lighter colored patches on the trunk, as you can see in this picture.  Woodpeckers make these marks as they feed on the tasty (to them) borers that are just under the bark. Once you start seeing evidence of EAB activity, your tree will most likely suffer severe dieback within three years. There is an insecticide treatment that can save your tree, but treatments need to begin before your tree is infested.  

For more information on EAB and treatments, please contact the Garden’s Plant Information Service or check out these sources:


©2013 Chicago Botanic Garden and my.chicagobotanic.org