Tag: pests

What’s old is new again

While the Emerald Ash Borer (EAB) continues to expand in the upper Midwest (see http://www.emeraldashborer.info/files/MultiState_EABpos.pdf  for a current infestation map), EAB is old news here in Michigan, especially in the southeastern part of the state.  Efforts to restore urban and community forest canopy lost to EAB will continue, however, for the foreseeable future. In 2003 we established an Ash Alternative Arboretum MSU Tollgate Education Center in Novi, MI – which is near ‘Ground Zero’ for the EAB infestation in North America.

 

The planting offers some insights into selecting alternative landscape trees to replace ashes.  A couple of elm cultivars, in particular, have emerged as shining stars in the demonstration planting that includes five specimens of 37 different species and varieties.  All trees were planted as 1½”-2” bareroot liners by Tollgate volunteers.  Tollgate farm manager Roy Prentice has overseen the maintenance of the planting.

 


Accolade elm (Ulmus japonica × wilsoniana ‘Morton’)  Compared to most of the other selections planted in the arboretum at Tollgate, Accolade elm looks like a man among boys.  Growth of these trees has been outstanding – the trunks of the trees have grown fast enough that they have split off their plastic rabbit guards (see photo).  Like Triumph elm, Accolade elm has dark green glossy leaves and develops into a large tree.  Although elms are often thought of ‘ugly ducklings’, both Triumph and Accolade are quickly developing well-formed vase-like crowns.

 


Triumph elm (Ulmus ‘Morton Glossy’) has also done very well at the Tollgate planting.  This elm develops a vase-like crown with age and has dark green, glossy leaves.  A large tree to 55’.

 

The elms are part of series of elm cultivars that have been developed with high tolerance of Dutch elm disease.  Most of the new elms are hybrid crosses with Asian and European elm species, though selections of American elm that are tolerant of Dutch elm disease are also available in the nursery trade.  The irony in all of this, of course, is that native American elms were devastated by another introduced exotic pest, Dutch elm disease.  As elm trees were rapidly lost during the 1950’s, 60’s, and 70’s, ash trees became a popular replacement due to their ease of transplanting, growth rate, broad site tolerance and pest resistance (yet another irony).  Now we’re promoting elms to replace ashes.

 


Street scene before and after Dutch Elm Disease.  Photo: theprincetonelm.com

The moral of the Dutch Elm Disease and Emerald Ash Borer stories is that it’s critical to avoid over-reliance on one species or even one genus – even a native one.  In Michigan some of our urban and community forests are over 50% maple.  As global trade increases and the potential for destructive pests to hitch-hike around the world rises, the best hedge against catastrophic tree loss is to plant a broad and diverse array of adapted trees.

Everything is obvious once somebody shows you…

It’s amazing how many things in life seem complex when we try to figure them out for ourselves but then we end up smacking ourselves on the forehead when someone shows us how simple it really is.  The infield fly rule comes to mind.  Some colleagues of mine here at Michigan State may be on their way to such a solution for the problem of white grubs in lawns.  Drs. Dave Smitley (Entomology), Kurt Steinke, and Trey Rogers (Crop and Soil Science) are investigating the effect of mower height on turf damage from grubs.

European chafer grub.  Photo: David Smitley

The premise is simple: White grubs damage turf when they consume about 75% of the turf roots present.  Raising the mowing height of most standard mowers from 2” to the highest setting (usually 3 ½”) also results in more root growth; often by more than double.  Since there’s a limit to how much root mass grubs can consume, increasing the amount of roots ensures the damage threshold is never reached.  The working hypothesis has been confirmed by greenhouse tests and now the researchers are taking to the field.


Chafer grub damage.  Photo: David Smitley

This may turn out to be another example of how raising mower height and not trying to make your lawn look like a golf course fairway can reduce inputs and keep your turf healthier.

Disney and Japanese Beetles

This past weekend I had the opportunity to speak at Epcot Center in Florida.  It was, without a doubt, one of the highlights of my career so far.  I spoke 6 times over the course of 3 days.  The focus of my talk was garden remedies.  I started by talking about Paris Green (a good story for next week), then made fun of some of Jerry Baker’s, Myles Bader’s and Joey Green’s recommendations, and then proceeded to talk about which homemade cures do and don’t work and why.  And then I asked the audience for questions.  I always ask the audience for questions at the end of my talks, but I’ve never had such a diverse audience before (both gardeners and non-gardeners from all across the country), so it was interesting to see which problems came up the most.  The winner was…. Japanese beetle with fire ants and deer coming in a close second and third.  With that in mind I thought I’d devote this column to Japanese beetle control.


Above is my newest prize possession — A statue of Mickey thanking me for speaking at Epcot

The first rule of Japanese beetle control is that you can’t control Japanese beetles.  Nobody has found a sure-fire cure yet and, if you try too hard, you’re going to poison yourself and everyone in your neighborhood.

The second rule of Japanese beetle control is like unto the first.  Don’t trust garden center employees to know a damn thing about Japanese beetle control.

The third rule of Japanese beetle control is not to make the problem worse that it already is.  Using a trap to lure Japanese beetles to their demise will kill a few — and may make you feel like you’re doing something — but you will be attracting more beetles to your yard than you kill.

The fourth rule of Japanese beetle control is that killing grubs doesn’t stop the adults.  In other words, while killing Japanese beetle grubs is possible (usually using imidacloprid), killing those grubs won’t prevent adults from flying into your yard after they’ve hatched from someone else’s yard.

The fifth rule of Japanese beetle control is that Japanese beetle control is dirty work. Most of the “organic” and biological controls just don’t work that well.  If you want to spray a concentrated dish soap spray on the beetles that will kill them, but it won’t last long and it will burn your plants.  Same thing with a spray of one of those citrus insecticides.  The organic insecticide pyrethrum will kill Japanese beetles, but it won’t last long and spinosad (another organic insecticide) which works for some beetles (it’s better on other insects)  just isn’t considered that great.  A biological control called Milky Spore Disease is supposed to kill Japanese beetles while they’re grubs, but the truth is that it usually kills less than 50% even in good conditions.

The sixth rule of Japanese beetle control is that, if you’re willing to go to a little bit of trouble, lose a few leaves, and use a little bit of a synthetic insecticide there is a way to protect your plants to some degree.  If you’ve ever been around these beetles then you’ll know that they prefer some plants over other — for example, they love roses, and so they’ll attack roses first.  If you spray roses with permethrin (a synthetic insecticide) you can get 7-14 days of clean roses, and, if you’re lucky, you’ll kill many of the Japanese beetles before they move on to other plants — this is called trap cropping.

The seventh rule of Japanese beetle control is that these beetles will seek revenge for their dead relatives.

Soap and Deer

Short post today — Linda appears to have transmitted her illness electronically over a couple of thousand miles — Thanks Linda!

I was reminded yesterday that it’s almost time for gardeners to start worrying about winter deer damage. With that in mind I thought I’d share with you my favorite research article on the subject.  It’s a little paper by Michael Fargione and Michael Richmond and published about 18 years ago.  You can find it here.

This paper attempts to establish how repellent bars of soap are to deer and comes up with some very interesting conclusions.  The first thing you should know is that no one type of soap appears to be better than another.  The second thing you should know is that soap does appear to stop deer from feeding around the soap — but the best you can hope for is a radius of protection of about a meter from the bar of soap itself — Can you imagine what that would look like if you were trying to protect the lower limbs of a large tree?  And finally, bar soap appears to attract voles.  Based on my reading, and my limited experience, I’ve found that almost everything that people say repels deer does repel deer — human hair, peeing around a tree, predator urine, dried blood — the issue is how long these repellents stay effective and how effective they are when the deer get really hungry.  The most effective commercial deer repellents tend to have “putrescent egg solids” in then (rotten eggs) — I once had a graduate student who needed to protect some hazelnuts from deer and she found that a mixture of a few eggs (2-4) mixed in a quart of water and sprayed onto the trees worked pretty well — and no, the eggs weren’t rotten.  This mixture should be sprayed about once every two weeks if possible.

Shoot your favorite ash

One of the biggest issues facing urban and community forestry in the eastern half of North America is the Emerald Ash Borer (EAB).  As most people are aware, EAB was accidentally introduced in Michigan some time in the late 1990’s.  By 2002 when the insect was found and identified, thousands of ash trees in and around Detroit were dead or dying.   Since then the insect has continued to spread, partly by natural dispersal but also by hitchhiking on logs and firewood. As of July 2009, EAB now occurs in 13 states and 2 Canadian provinces.  To date, researchers have not found any indication of resistance to EAB in North American ashes.  This includes green ash and white ash.  Based on our current understanding of the insect, EAB has the potential effectively eliminate the ash genus from North America, similar to effect of chestnut blight on American chestnut or Dutch elm disease on American elms.  To help stave off the demise of ash to EAB a veritable army of university and government researchers are conducting wide array of trials to identify chemical or biological controls that can save ashes.  Several insecticides can be effective but so far are only feasible for use on high-value landscape trees due to the cost of application and the need to re-apply treatments every 1-3 years depending on the chemical.

To help build awareness of the destructive potential of EAB and the impact of losing ashes in North America, I invite readers of the Garden Professor’s blog to share photos of their favorite ash.  Photos can be e-mailed to me @ cregg@msu.edu and I will post them on the blog.  Include any pertinent information about the tree(s).  To get things started I have included photos of ash trees surrounding the Gateway arch in St. Louis.  In the early 1970’s over 500 ‘Rosehill’ white ash trees were planted along the sidewalks in the park area surrounding the arch, which was completed in 1967.  The ash trees frame the famous ‘Gateway to the West’ and provide shade to cool visitors during St. Louis’s sweltering summers.  Unfortunately, the ashes may ultimately serve as a cautionary tale of the perils of monoculture in landscape design if they are lost to EAB.  The National Park Service, which manages the Gateway Monument grounds has begun to plant new trees from a variety of species.  However it will be years before those trees will be anywhere near the size of the existing ash trees.  To date, EAB has only been found in Missouri in an isolated outbreak in the southeast corner of the state but the insect has a firm foothold in Illinois and is moving westward. The ashes in the Gateway monument are being monitored for EAB and presumably the Park Service will begin treating the trees with trunk injections of systemic insecticide if EAB are detected in or near the Monument.
Ash trees frame the Gateway to the West

Over 500 'Rosehill' ash trees line the walkways at the Gateway National Monument

Voles are Pickier Than You Think

…and it’s not just the scientifically-proven inverse correlation between the price of the mail-order perennial and likelihood it will get chomped within six months. The prairie vole (Microtus ochrogaster) is notorious throughout central and eastern North America for laying waste to many a well-tended garden. Much of what’s out there in regards to herbivory of ornamental plants (said chomping by deer, voles, bunnies, etc.) is simply anecdotal, yet repeated ad nauseum as fact. So it’s exciting to see some new research in that field, published in a recent HortTechnology journal.

Dr. William Miller’s research focus is bulbs, and his group at Cornell University set up feeding trials with thirty common garden bulb species to quantify the prairie vole’s preference thereof. Tulips topped the list as the colony’s favorite (but you knew that already). In fact, “the voles became accustomed to this feeding schedule, and would vocalize and get excited when we entered the laboratory to prepare the bulbs…”

The voles showed the least interest in daffodil (Narcissus), grape hyacinth (Muscari armeniacum), Italian arum (Arum italicum), ornamental onions (several Allium species) and snowdrop (Galanthus nivalis). These bulbs were evidently high in the sort of secondary metabolites that, among other things, cause plant tissue to taste bad. There were even preferences shown as to different cultivars within each species – they were wild about tulip ‘Apeldoorn’ yet ate half as much of the species Tulipa turkestanica. Note to the vole-ridden…the daffodil ‘Ice Follies’ registered barely a nibble.

Apparently voles love apples more than anything, so the researchers also mixed dried, ground bulbs with applesauce to make them even more appealing. The point of this slightly eludes me, but the take-home message was 1) voles will eat anything except onions when mixed with applesauce, and 2) don’t dip your bulbs in applesauce prior to planting. Now if only Dr. Miller would work on vole feeding preferences by price point…

Source: Curtis, B, D. Curtis, and W. Miller. 2009. Relative Resistance of Ornamental Flowering Bulbs to Feeding Damage by Voles. HortTechnology 19:499-503.

Slugs and Beer: Not So Fast, My Friend…

[To those new to our blog, there are many past posts of scientifically-proven garden advice and research results…so pardon if we slip off the wagon just briefly.]

In response to the previous post:
Dr. Gillman, I’m simply shocked at your sloppy “materials and methods”.
What is that, a Frisbee? And you drink a beer called Moose Drool? Sounds intriguing, but probably too hoppy. No wonder the slugs were simply mocking your feeble attempts at attracting them.

BEHOLD the well-researched and insightful slug trap:

One 12″ plastic pot saucer + 10 oz. Pabst Blue Ribbon = 28 slugs in one night.

Not unlike college students, results indicate there’s obviously no accounting for the slug’s taste (or lack thereof) in beer. Hmmm…that gives me an idea for a grant proposal…

Slugs and Beer

Around my home I have gravel and hostas.  Just perfect, as you might imagine, for lots of slug damage.  This is where I do my work on slug remedies.  And there are lots of remedies for slugs!  One of the oldest of these remedies is beer.  Almost any beer will be adequate (including alcohol free), but generally the darker the beer the better.  When I first started testing different cures for slugs about five years ago one of the first ones that I looked at was beer.  And when I first tried it…..well, see for yourself.

This is the way that I set up my first beer trap (for this test).  There’s fine sand all the way around the trap and the trap is filled with Moose Drool (a nice beer — Suzanne, my wife — was actually a little irritated that I wasted a good Moose Drool when we had a Bud Light in the fridge — But I was only thirsty for half a beer when I set it out….and I don’t like Bud Light)

I set this trap up around 8 o’clock on a nice warm summer evening, the idea being that the next morning I could go out and see how many slugs approached the beer (by looking at the sand) and then see how many slugs the beer actually caught.

As you can see below we had quite a few slugs approach the beer (By my count about twenty).  And guess how many dead slugs were in that beer?

If you guessed 20…you’d be wrong!  There were no slugs in that beer.  Why?  Because this is a poorly designed slug trap!  slug traps are best when they are made with something like a mason jar and that jar is buried up to the lip of the jar in soil.  Then the jar should be filled up to within about an inch of the top with beer.  If you fill it higher the slug will be able to just reach his head in and drink.  In fact, after I set this trap out, I spent much of the evening watching slugs do just that — it was actually a little like watching old episodes of Cheers!  I had names for the slugs and everything (like Norm and Frazier and that mailman guy whose name I can’t remember now…).

So slug traps are good — but only if they’re set up right!

Bags and Apples

One of my favorite garden “cures” is placing a clear plastic sandwich bag around apples when they are young to protect them from insects and disease.  It usually works great and impresses the heck out of people who see and eat the apples which are normally tough to grow without using  bunches of organic or synthetic pesticides.

Unfortunately this year was different.  Rebecca Koetter, the person who planted these trees and put the bags on the apples (on the University of Minnesota campus) discovered that birds may choose to ignore the bags.  And, as if that wasn’t bad enough, Asian lady beetles decided to get in on the fun!