Bert Cregg

Imprelis damage to landscape conifers

Herbicide issues seem to be dominating my life these days. Over the past several weeks reports have surfaced around the Midwest of landscape conifers – primarily spruces and pines – that have developed rapid and severe die-back. While there are a host of insect pests and pathogens that can cause die-back in conifers, the recent cases are noteworthy in the speed with which trees expressed symptoms.

Photos: Andy and Carol Duvall

In many cases that have been reported the common thread appears to be the use of Imprelis, a turf herbicide developed and marketed by Dupont. Imprelis (active ingredient: aminocyclopyrachlor) is a synthetic auxin designed to control broadleaved weeds in turf. Ostensibly, one of the advantages of Imprelis is that has root activity in addition to foliar activity. It appears, however, that it may have too much root activity and the internet is abuzz with photos and posts of Imprelis-damaged conifers. http://bestlawn.info/northern/imprelis-and-dupont-trouble-t4608.html

http://www.buckandsons.com/blog/tag/dupont-herbicide-imprelis/

So what’s going on? Well there are lots of blurbs coming out and lots of things being reported second and third-hand. I suspect a few things we ‘know’ about Imprelis right now will turn out not to be the case in a few months. Dupont has tried to shift blame to the applicators, suggesting that their rates may have been off, they applied when there was potential for drift, or that the material was mixed with other herbicides. http://www.ksuturf.org/blog/wp-content/uploads/2011/06/DuPont-Letter-to-Turf-Professionals-061511.jpg

Given that reports of damage showing similar symptoms have come from Kansas, Iowa, Indiana, Michigan, and Ohio it seems unlikely that everyone is mis-applying the product. I suspect one of a couple things may be going on. Dupont may have underestimated the lateral extent of tree roots, especially for conifers that often have shallow, extensive root systems. It’s also possible that Norway spruce and white pine are more sensitive to this product than whatever Dupont tested it on.

In the meantime stay tuned. In case people haven’t figured it out for themselves, Dupont now recommends that applicators not use Imprelis near spruces or pines (see letter linked above). Landscapers or lawn service operators that have applied Imprelis should keep in touch with their state Department of Agriculture and their professional turf and landscape association. Might be good to fasten your seatbelts, this could be a bumpy ride…

Excerpt from Davis et al. letter to Nature on natives vs aliens

In yesterday’s post I linked to a letter in Nature by Mark Davis and a number of other ecologists on the role and native and alien plants. Unfortunately the journal requires a subscription. Copyright laws prevent me from re-printing the entire article, however, below is an excerpt from the conclusion, which I think captures most of their message.

“Most human and natural communities now consist both of long-term residents and of new arrivals, and ecosystems are emerging that never existed before. It is impractical to try to restore ecosystems to some ‘rightful’ historical state. For example, of the 30 planned plant eradication efforts undertaken in the Galapagos Islands since 1996, only 4 have been successful. We must embrace the fact of ‘novel ecosystems’ and incorporate many alien species into management plans, rather than try to achieve the often impossible goal of eradicating them or drastically reducing their abundance. Indeed, many of the species that people think of as native are actually alien. For instance, in the United States, the ring-necked pheasant, the state bird of South Dakota, is not native to the great plains of North America but was introduced from Asia as a game bird in the latter half of the nineteenth century.

“Specifically, policy and management decisions must take into account the positive effects of many invaders. During the 1990s, the US Department of Agriculture (USDA) declared several species of introduced honeysuckles to be alien (harmful), and banned their sale in more than 25 states. Ironically, from the 1960s to the 1980s, the USDA had introduced many of these same species in land reclamation projects, and to improve bird habitats. Recent data suggest that the agency’s initial instincts may have been appropriate. In Pennsylvania, more non-native honeysuckles mean more native bird species. Also the seed dispersal of native berry-producing plants is higher in places where non-native honeysuckles are most abundant (Gleditsch, J. M. & Carlo, T. J. Diversity Distrib. 17, 244-253 (2010).

“Clearly, natural-resource agencies and organizations should base their management plans on sound empirical evidence and not on unfounded claims of harm caused by non-natives. Another valuable step would be for scientists and professionals in conservation to convey to the public that many alien species are useful.

“We are not suggesting that conservationists abandon their efforts to mitigate serious problems caused by some introduced species, or that governments should stop trying to prevent potentially harmful species from entering their countries. But we urge conservationists and land managers to organize priorities around whether species are producing benefits or harm to biodiversity, human health, ecological services and economies. Nearly two centuries on from the introduction of the concept of nativeness, it is time for conservationists to focus much more on the functions of species, and much less on where they originated.”

Ecologists weigh in on native-exotic debate

Charlie Rohwer, a frequent guest contributor to the Garden Professors, brought to my attention a recent letter in Nature by Mark Davis and 18 other ecologist entitled, “Don’t judge species on their origins.” Davis is a leading authority on invasive species and author the book Invasion Biology. In their article, Davis and his co-authors make many of the same points that I’ve made here on the blog (Are natives the answer? Dec. 14, 2009; Restoration ecologists you need us – part 2. Aug. 9, 2010) regarding the native/exotic debate. The main point is that we need to develop a more pragmatic approach to managing landscape systems and this includes natives and exotic species; it’s not an either/or question anymore, not that it ever really was.

A couple of excerpts from their letter:

“It is time for scientists, land managers and policy-makers to ditch this preoccupation with the native–alien dichotomy and embrace more dynamic and pragmatic approaches to the conservation and management of species — approaches better suited to our fast-changing planet.”

The pragmatic approach that Davis and his co-authors (and I) advocate recognizes a several realities:

Exotics can fill many of the same ecological roles and niches as natives, Doug Talamy’s book notwithstanding.

Any inherent “ecological superiority” of natives over exotics has long since been negated by anthropogenic land-use change, alien pests, and climate change.

Attempts to eradicate alien species are largely warm-fuzzy exercises with little likelihood of success without liberal use of industrial-strength herbicides.

Read and follow label directions…

Every extension specialist or educator that mentions any kind of pesticide in a talk or article always includes the disclaimer ‘Read and follow all label directions.” However that caveat ranks somewhere between “Your seat cushion may be used as a flotation device” and “Do not remove tag under penalty of law” as the most ignored phrase in the English language. While we can probably rationalize ignoring the last two (If a jetliner ditches in the middle of the Atlantic is a seat cushion really going to save you? And when was the last time you saw someone led away in handcuffs for pulling the tag off a mattress?); failing to pay attention to pesticide labels can have some real and immediate consequences.

I got called recently to inspect some tree and shrub damage at an industrial park in suburban Detroit. (Because the case potentially involves some legal issues, I won’t mention names of any parties). The industrial park included several hundred acres, much of it turf and landscape beds of trees and shrubs. The park had its own groundskeeper but contracted out its spray applications. A couple summer’s ago the staff groundskeeper complained several times to the contractor that they weren’t doing a sufficient job of keeping up with the weeds in the landscape beds. The typical vegetation management tools of choice on this site were spot applications of Round-up (glyphosate) and hand-weeding. For reasons that are not completely clear, this time the contract applicator reached for a jug of Sahara. Even if you don’t know what Sahara is; what image does the name conjure up? Parched. Barren. Lifeless. Sahara is a combination of two herbicides (Diuron and Imazapyr) designed for complete vegetation control in non-cropland areas such as parking lots and rights of way. And, unlike Round-up, Sahara provides foliar and root activity. This is a product you use when you want complete burn-down and you don’t want anything growing there for a long time.

A hedge maple 2 years after herbicide application

Unfortunately, that was not the desired result in this location. Within a week of the application, dozens of trees and shrubs all over the industrial park were either dead or wishing they were dead. The smoking gun was not too hard to find. The applicators had duly noted the herbicide application in their logbook and presence of active ingredient was confirmed in soil samples. Although the parties are still working a settlement, the bids for replacing the affected trees and shrubs are well into six figures.

The unkindest cut of all. These green ash were regularly treated with imidacloprid to protect against emerald ash borer. An herbicide ap took them out instead.

Two years after application there are still bare zones where Sahara ran off from mulch rings and landscape beds.

Of course, all of this death and destruction (and legal wrangling) could have been avoided simply by… Reading and following the label directions. The Sahara label notes in several places that contact with roots can damage trees and other plants, including this explicit statement under a heading in all bold letters, PRECAUTIONS FOR AVOIDING INJURY TO NONTARGET PLANTS: “Injury or loss or desirable trees may result if Sahara is applied on or near desirable trees or on areas where their roots extend.” Sounds pretty clear to me folks – don’t use this stuff near plants unless you want them to die.

So, next time you or someone working for you has any question about what a pesticide does: Read and follow label directions….

Getting to the root of the problem

After getting off to a cool and soggy start, summer has come with a vengeance to Michigan, with heat indices expected to push 100 degrees by Wednesday. Along with warmer temperatures, summer also means our research season is getting into full swing as well. One of our biggest efforts these days involves our project to look at pre-plant storage and handling on shade tree liners.

As many GP blog readers are aware, emerald ash borer (EAB) has dominated the conversation regarding shade trees in the Midwest for the past 6-8 years. Ashes made up 20 to 30% of the shade tree cover in many urban and community forests, so their loss has been devastating. A major thrust of our extension programming during this time is to promote a wide range of ash alternative to increase species diversity. One of the challenges we find in making this pitch is that many of the species we recommend (oaks, hackberry, baldcypress) are trees that nurseries often find difficult to grow from standard bare-root liners.

My graduate student, Dana Ellison, is in the second year of a project to look at some of the practices that growers use on the difficult to transplant species and some of the underlying causes of poor transplanting. Dana is looking at a variety of attributes including plant water relations and carbohydrate status, but the order of business these days is roots. Specifically we’re evaluating root growth potential of oak, baldcypress, and hackberry. We’ve also included white ash, which transplant easily, as a positive control.

Graduate research assistants Dana Ellison (right) and Brent Crain (left) and undergraduate assistant Arriana Wilcox (center) pot up shade trees for root growth potential testing.

Root growth potential (RGP) is a common parameter in evaluating quality of reforestation seedlings but is measured less often on larger liner material. The logic is pretty straightforward; a plant’s ability to initiate root growth after plating and re-establish root-soil contact is one of the biggest determinants of its ability to survive and grow. A variety of systems have been used to evaluate RGP for seedlings – most involve growing seedlings for a set time (3 weeks is standard) in an aeroponic system and then counting or measuring new root growth.

Growing the trees in pea gravel makes it easy to get a look at new roots.

For Dana’s shade tree liners (5’-6’ whips) we’ve adapted a system based on the Missouri gravel bed system (which I first got to see in person at Jeff’s research nursery in Minnesota – thanks Jeff!). Dana and her helpers pot the trees up in pea gravel in 25-gallon containers. The trees are grown on for three weeks in a greenhouse while the roots are kept moist with spray stakes operated by a mist system timer. After three weeks, we dump out the gravel, wash the root systems, and carefully count the number of new, white root tips.

Dana washing roots.

So what have we learned? Well, the work is still on-going but some trends have emerged. Baldcypress may experience some transplant issues but they don’t appear to be related to producing roots. We had several baldcypress trees that produced 400 or more new roots during the RGP test – and, yes, we counted them all! Red oak and northern pin oak, on the other hand, are very slow to put out new roots. For hackberry trees, our other measurements suggest their transplanting issues may be related to their inability to re-hydrate after lifting, storage and transport. These insights should help us provide some guidelines to growers to help them produce a wide pallet of trees for the landscape market and increase species diversity in the wake of EAB.

Counting roots. Almost as much fun as it sounds…

The defending champion baldcypress: 614 new roots.

Safety first?

I was driving around town recently and saw a tree service crew clearing up some storm damaged trees. Because of my line of work I usually do a little rubber-necking and try to assess why type of tree came down and what issues may have preceded it’s demise. In this case, however, I was struck not by the trees but by the tree crew. What I saw left me speechless. Well, here, see for yourself…

No eye protection. No hearing protection. No sign of a hardhat, face-shield, or chaps by the chainsaw. No personal protective equipment anywhere as near as I could tell. Of course the photo illustrates a lot of what’s wrong with the landscape and tree service industry. Economists tell us that this industry has a ‘low barrier to entry’; in other words any one with a chain saw and a pickup truck can put an ad in the classifieds and call themselves a tree service. As a consumer, you may not care if the employer makes their employees where personal protective equipment (PPE). But if they don’t care about their employees’ safety, what else don’t they care about?

Periodically I’ll write an article for a newspaper or other media on selecting an arborist. I always make the point that you get what you pay for and urge consumers to compare bids and companies carefully. Truly professional tree services have to cover the cost of hiring and retaining quality employees, worker training, proper equipment (including PPE), and insurance. If you skip over those things, like Fly-by-night tree service here, it’s probably not too hard to come out with the low bid.

Science Education and Lichens

Seemingly once a week we see a report in the news about how Science and Math education in the US lags behind many developed countries around the world. http://articles.cnn.com/2011-05-15/us/education.obrien.response_1_math-and-science-national-robotics-competition-education?_s=PM:US

While we typically think of Chemistry and Physics when discussing science education, biology is in there too.

I bring this up because I am continually amazed at how little many people know about basic biology. Some of this funnels its way into extension calls and e-mails. A couple of weeks ago I got a call from a distraught homeowner in a Detroit suburb. “My maple trees are dying”, he told me sincerely. “There are growths all over them. They’re big trees. What do I need to do to save them?”

I tried to get as much information as I could over the phone: How old are the trees? What kind of maple? Describe the site. Describe the symptoms. I told him the problem didn’t sound like typical issues with maples in our area (i.e., not manganese chlorosis, tar spot, gall mites, or verticillium wilt). Diagnosing problems sight unseen is difficult so I asked if he could get me some digital photos. “Yeah, my son has a digital camera. We can do that.” Later that week I got a series of digital photos like the one below.

Lichens on maple

I informed him the growths on the trees were lichens, a combination of a fungus and algae; they’re normal and they don’t harm trees. I gave him a quick biology lesson on lichens and pointed out that some of the pictures he sent were of lichens growing on the sidewalk. The algae part of the lichen is photosynthetic so they just need a place to hang out – a tree, a sidewalk or a piece of wood all work fine.

British soldier lichens

One of my all time favorite bumper stickers says, “If you think education is expensive, try ignorance”. I suspect if this homeowner had happened to call an unscrupulous tree service instead of MSU Extension, they would have been more than happy to ‘treat’ the problem and sign him up for their deluxe 8-step pest and micro-nutrient maintenance plan. Sometimes a little knowledge can go a long ways.

Creating a sense of place

As many GP readers know I’m originally from Olympia, WA. Once a week or so I troll through the on-line version of my hometown newspaper, the Daily Olympian (“the Daily ‘O’” for short or, more commonly, “the Daily Zero”) to keep up with latest happenings back home and to see if any of my high school classmates are on their way to jail. While none of the Olympia High Class of ’78 made the news recently, my interest was piqued the other day by the headline “Saving the world – from weeds”. The article described the Earth day efforts of local grade-schoolers to eradicate Scotch broom from a local nature trail.

http://www.theolympian.com/2011/04/23/1626461/saving-the-world-from-weeds.html#storylink=misearch

For those that are not familiar, Scotch broom is an exotic shrub that commonly invades disturbed areas throughout the Northwest. It’s been a problem for years and, even as a kid 40 years ago, I remember every cutbank around town covered with the nasty yellow blossoms. In doing a little trolling on the internet I was surprised (stunned is probably a better word) to learn that there are parts of the country where Scotch broom is still sold as an ornamental shrub – named cultivars and all. There are commercial cultivars of dandelion after all, so why not?

As we’ve noted here on the GP blog, there are lots of layers of complexity to the native/non-native discussion. In many cases I think native advocates have over-sold the ecological side to the argument. But the Daily O article got my dander up; not because 4^th graders were pulling up Scotch broom – good riddance and keep up the good work kids – but because the Scotch broom was replaced with trees and shrubs that were all exotics in that part of the Northwest.

Native plant advocates often downplay the ‘sense of place’ argument in promoting natives. I suppose they feel the ecological arguments are based on ‘harder science’ and therefore more convincing. While it can be argued that native plants have adapted to the environment in which they evolved; it’s not always a given that the native conditions still exists, particularly in the built environment. What’s beyond argument, however, is that trees and other plants provide a connection to the natural world around us and, for lack of a better term, do give us a sense of place. From my personal experience, I have a visceral reaction to the sight of Scotch broom or English ivy in the Northwest where I’m native. Here in Michigan, on the other hand, I’m less bothered by exotics – even some that may be considered invasive. I suspect many native-born Michiganders have the opposite reaction.

I’m sure part of my connection to all things Washington stems from lessons learned in school (I still know all the lyrics to ‘Washington my Home’ and my plant collection form Mr. Chance’s high school Botany class is still somewhere in the attic of my parent’s house). Which is why I was flummoxed by the schoolkids planting tulip poplars and sequoias instead of big leaf maples and western redcedars. Wouldn’t this exercise have been a great opportunity to teach these young people about the great trees and shrubs that are native to the Northwest and to give these kids a sense of place?

These are a few of my (least) favorite things…

Spring clean-up came in earnest this weekend at Daisy Hill farm. Everything will be downhill from here as my least favorite yard chore; cutting back our ornamental grasses, is done for the year. I know, I know, there are all kinds of shortcuts and tricks for this job including lassoing grasses for the last round-up (see Holly’s March 8 post), duct-taping them, and cutting them down with hedge-trimmers or a chainsaw. Unfortunately, between our winter snow beating them down and our dogs using them as their own personal jungle playground, standing the grasses up neatly to await a trim just isn’t an option. So I dive in and do it the old-fashion way; armed with a set of hand-loppers, every piece of personal protective equipment I can find, and the entire repertoire of swear words my Army sergeant Old Man taught me. Between hacking, cussing, and hauling it’s a two afternoon job. On the plus side, it did give me time to ponder my top five list of least favorite yard jobs. See how it compares with your list…

Cutting back ornamental grasses
Picking up black walnuts (this is to Fall what no. 1 is to spring)
Weeding (the only redeeming factor is instant gratification)
Deadheading (yeah, it’s not the hard but you know you’ll have to turn right around and do it again (and again and again…)
Leaf raking (Actually, this wouldn’t be so bad but I went out and bought a chipper-shredder a couple years ago and feel compelled to use it. Works like a champ – shreds leaves as fast as I can feed them in. Too bad the bag needs to be emptied approximately every 43 seconds…)

Who you gonna call?

As I noted last week, this has been a long winter in Michigan – OK, Jeff, no chortling from the frozen tundra of Minnesota… Most gardeners in this area have only been able to do their spring yard and garden clean-ups in fits and starts as the weather allows. We’re finally warming up a bit this week but now strong storms are in the forecast. One of the things gardeners will want to do is to size up any winter damage that has occurred since they put things to bed last fall. Although our winter was long, it was otherwise unremarkable with few temperature extremes – low or high – that would likely cause problems. In fact, aside from some heavy snow in February, the winter of 2010-11 was probably the closest thing we’ve had to a ‘normal’ winter in the 11 years I’ve lived in Michigan. Nevertheless, we will still be taking numerous extension calls on what we would consider ‘typical’ winter damage to trees and shrubs.

In this neighborhood not too far from my house, deer have declared open season on arborvitae.

One of the biggest issues we face is wildlife damage. The two biggest sources of problems are small mammals and deer. Small mammals such as mice, rabbits, squirrels and voles cause damage mainly by gnawing on trunks and branches. Despite their small size, these animals can kill trees by removing bark and underlying tissue around the circumference of a tree trunk, a process referred to as ‘girdling’. If a large portion of trunk circumference has been girdled, trees are unable to move energy reserves between roots and shoots, and will eventually die. Deer can cause extensive damage to trees and shrubs due to feeding and also through rubbing their antlers. Deer feeding is often indicated by a ‘browse line’ based on how high deer can reach. Rub damage from deer antlers can cause major deformation to trunks and can even kill trees by girdling. I was in a new subdivision in the East Lansing area this weekend and well over half of the trees on the tree lawns will need to be replaced due to extensive deer rub damage.

At least half of the trees in this entire subdivision will need to be replaced due to deer-rub damage.

Dealing with wildlife damage is a complex issue and varies with local conditions and wildlife pressure. Fortunately, wildlife experts from several universities (Cornell, Clemson, Nebraska, Utah State) have organized the Internet Center for Wildlife Damage Management. http://icwdm.org/ This site is one of the best resources I have run across for assessing and dealing with wildlife damage issues. If you’re in a position where you have to deal with wildlife damage or advise clients about damage, this is a useful site to add to your bookmarks.