Imprelis update

I’ve been continuing to track some of the reports of injury to conifers associated with the new herbicide, Imprelis.  Interest in the problem is likely to escalate given a front page article in the Sunday’s Detroit FreePress. http://www.freep.com/article/20110710/NEWS06/107100467/New-lawn-chemical-chief-suspect-mysterious-deaths-trees

 

I visited about ten sites last week with an applicator that had used Imprelis this spring.  The landscaper was a certified applicator with about 15 years of experience with herbicides, insecticides and fungicides, who was knowledgeable about his chemicals and plants. We saw bout 50 trees, mostly pines and spruces with varying levels of injury.  The typical symptoms were brown or off-color needles, and stunted or twisted shoots.  Damage was mostly limited to the current flush of growth, resulting in a distinctive pattern of growth.  In many cases, there was evidence of spiral movement up the trunk of the tree.  The most rapid growing points (usually terminal leaders) were most severely affected.  Based on my experience with other forms of herbicide injury and other types of environmental damage, I suspect all but the most severely injured trees would recover is given enough time and some corrective pruning.  The problem, of course, is that most homeowners don’t want to wait around while the tree in their yard tries to rally.

Some photographic ‘highlights’

 

The $64 question now becomes, “What happened?”  In order to receive registration from the US EPA, each new herbicide has to go through extensive testing.  According to DuPont, over 400 tests were conducted with Imprelis.  Despite some claims elsewhere on the internet, this testing included independent university trials on spruces and pines at up to 4x the labeled rate.   The key to unlocking the mystery of Imprelis injury will probably lie in understanding how conditions in actual application conditions differed from the testing.

Hot weather and not-so-hot advice

Today I was sent a link to a posting on “droopy leaves.”  Essentially, it suggests that droopy leaves are a means to conserve water on hot days and that watering these plants causes more problems than it solves because the roots don’t get enough oxygen.  A link to the science of transpiration is provided.  The advice is to wait until the evening and if the plants perk back up, then they didn’t need water after all.

This is one of those maddening articles that has enough science in it to make it sound reasonable, but is ultimately incorrect in its assumptions and advice.  It’s worth looking at the topic in a little more detail.

Some plants are adept at conserving water in hot weather.  Their leaves tend to be small, thick, with a heavy layer of waxes protecting the surface.  Leaves can also move to limit their sun exposure and thus reduce the heat load.  But wilting is not a method of conserving water.  Instead, it’s a sign that water loss (evapotranspiration through the leaves) exceeds water uptake from the roots.  And if you ignore wilt, you do so at your own peril.  Once terminal wilt is reached, it’s all over for that part of the plant.


Wilt.  Sorry it’s a fuzzy photo.

Large, thin leaves, common in many of ornamental, annual and vegetable species, do not conserve water.  Tomatoes, zucchini and black-eyed susans, the plants specifically mentioned in this article, are not water conservers.  Chronic wilting of these and other can eventually cause leaf tip and margin necrosis (or tissue death).  It also reduces growth, so that your yield of tomatoes, zucchini and black-eyed susans will be decreased.

Leaf tip and marginal necrosis from chronic drought stress

So yes, do water your plants if they are wilting in the midday heat!  Use mulches to conserve water!  (You’ll notice in the photograph on the linked site that the plants are in bare soil.)  Fine root systems are generally near the soil surface, and keeping these hydrated keeps them alive.  You won’t see an instantaneous response to watering if plants are already wilting, but they will recover – much better than if you don’t water them at all.

Chlorosis mystery uncovered – maybe

Sorry about the long wait in discussing the weekend’s post!  (Technical troubles with access here in BlogVille.)  In any case, many of you zeroed in on the defunct lime kiln as a possible pH adjuster.  It would have been really interesting during those years to see how materials were processed – for instance, was there a lot of lime dust that settled over the area?  Where did the limestone come from – was it carted in by train or was it local?  Were chlorosis problems visible then?

In any case, my educated guess is that a lot of limestone chunks brought to the area for processing were left scattered around the site and were eventually buried over time.  Plants recolonized the area, but where these chunks of limestone are sited we have pockets of chlorosis.  The only way to tell for sure would be to test the soil pH, and I did not have pH strips in my backpack.

An artifact from the old settlement, long since covered by the forest.

Consternation in the You-Pick Field

It’s high season at our blueberry farm.  Each morning, the yard fills with cars (at 7:00 a.m. – aargh) and eager blueberry pickers hit our four acres of Northern Highbush berries. No late freezes, lots of hard work by our honey bees, and good rainfall have added up to a blockbuster crop.  Certainly helps with the mortgage.

Running a you-pick ( U-Pick makes me itch) farm is an …interesting experience.  Upside – you do the picking, we weigh the buckets, we take the money – $2.40/lb + tax. Very reasonable for big, fat berries. Our average sale is right around 10 lbs.  I’d (theoretically) invite 90% of our customers to stick around for dinner – they’re that nice.  Downside, besides hot, grumpy children, bee stings, and porta-potties: some people literally eat their way across the field.  We absolutely expect pickers to taste a few as they go.  That’s part of the you-pick experience.  But I have witnessed some remarkable acts of blatant face-stuffing.  Kids, I can kind of understand, but adults? I mean, do you eat your way through the produce section of the grocery store? The truly noble customer recognizes this and offers an extra dollar or two (“Gosh, I may have eaten a lot”).  But the clueless #%$& who eats with both hands for an hour and then pays for a pound makes us a bit queasy. We get reports all the time from concerned customers i.e. “See that guy in the brown hat? He’s eating more than he’s picking.” One incident that comes to mind is a lady that completely denuded a 6′ plant; encouraging her daughter to eat the whole time, and then paid for less than a pound.

We try not to sweat it – maybe it’s a compliment as to how good our blueberries are – but it still puzzles me. What am I missing here? Why is this acceptable?  Taking a tip from another local farm, we put out a jar near the register last week.  They call it a “sin jar” but that’s a little too judgmental for us.  We call it “munch money” and note that the contents of the jar goes to our local woefully-underfunded animal rescue and shelter. We make a donation yearly anyway; now it’s more fun (and satisfying), served up as a gentle nudge  – we raised $120 for the shelter over the 4th of July weekend alone!

 

Interveinal chlorosis mystery

Today my family took our annual 4th of July weekend hike.  We ended up on a fairly new trail through the Robe Canyon Historic Park.  It was a gorgeous day and we saw all manner of plants and animals.  The highlight of this trail is an old lime kiln; bricks and other remnants of early settlers are scattered around the area.  The kiln closed in the 1930’s.  (The hot link embedded in the park name leads to a 2004 article about the trail and the history of the site.)

Ever on the lookout for interesting plants or plant problems, I found many of our native species with definite signs of interveinal chlorosis.  This is indicative of a foliar deficiency of iron or manganese. These forest soils are rarely deficient in either nutrient, and they also tend to be acidic (meaning that it’s easy to take up iron and managanese; alkaline soils inhibit uptake).

So why are these native plants, naturally growing on native soils, showing iron and/or manganese deficiency?Answer on Monday!

 

What Happens to the Horticulturist?

A couple of weeks ago I had the opportunity to talk with a professor in the agronomy department who’s going to be retiring very soon.  We talked about education and field trials, corn and trees, and then we started talking about the future of our departments.  Both of us are concerned that this generation of horticulturists (and agronomists—but I’m just going to deal with horticulture here) will be the last.

Over the last 10 or so years we have been losing horticulture departments.  Because of smaller budgets colleges and universities have combined hort departments with other departments to save money.  But I don’t see this as a major problem, after all, a rose by any other name would smell as sweet (OK – truth is I don’t know many sweet smelling horticulturists).  Horticulturists can be in departments besides horticulture and still do their job…But what is the job of a horticulturist at a university?

There will be all kinds of opinions on the “real” job of a horticulturist, but I believe that a big part of being a horticulturist is being a generalist – knowing a little about a lot of different things – insects, plant disease, soil.  We’re a little like a general practitioner who can take care of basic stuff and then refer the client to a specialist if needed.  Though most of us work with a particular type of crop (historically horticulture was split into 4 large groups – floriculture, fruit, vegetables, and landscape horticulture), horticulturists generally know enough about other crops so as not to make too much of a fool of themselves if they talk in general terms.  We know how plants work, and we know how the environments around them work to help them grow.  We are, in many ways, applied ecologists who are concerned about landscapes and the production of what many consider “minor” crops (at least compared to corn and soybeans!).

The biggest problem, as I see it, is that we are not hiring, or training, the number of horticulturists we once did.  In colleges and universities a premium is placed upon hiring faculty members who can acquire big dollars through federal grants.  The government likes “sexy” research which, right now, includes things like genetic engineering and biochemistry.  The government is open to having this work done on crops like apples and onions, or even nursery stock.  The problem is that generalists don’t tend to have the specialized knowledge in genetic engineering or biochemistry to do the work.  Hence, a biochemist or molecular biologist is hired and, hopefully, gets the grants the university needs.  But, in my experience, rarely do they really understand the crops they’re working on in terms of actually growing it.  Some do of course, but in the cases where they do it tends to be after the fact – in other words they learn about the crops after they begin working on them and their knowledge is often very basic.  I suppose this is OK, but to me it is sad that we’re not hiring what I consider true horticulturists anymore.  And, because we’re not hiring true horticulture faculty we’re not graduating many horticulturists from our graduate schools either.  Sure, we’re graduating molecular biologists and biochemists – and even a few breeders (who very often are horticulturists) – but these students may or may not leave a university with knowledge of “horticulture” as a whole.  And if we don’t start hiring more horticulturists what will happen?  Who will teach our introduction to horticulture course – or will horticulture just fragment and we’ll all need to go looking to specialists.  I don’t know, but it bothers me.

A Garden Professor migrates east, albeit briefly

I was AWOL last week, as I had 3 presentations to get ready for 3 different states all in the span of 4 days.  Yow!  But they are over and done, and I’ll try to keep up on the blog from now on.

This is a short but amusing post (to me anyway).  My second talk was in Virginia, where I spoke to Master Gardeners at their annual conference.  The speaker right before my talk was fellow GP Holly Scoggins.  (Note to self: never agree to follow Dr. Scoggins again.  I’m not nearly as amusing, though I am almost as tall.)

Anyway, Holly was discussing garden trends among other things and mentioned meta-gardens.  Hmmm.  I hadn’t heard of these, but assumed that, like meta-analyses, they were probably gardens that showcased plant collections from other places.  Kind of like arboreta but smaller, and maybe something you could do at home.  I nodded wisely, pretending that I was fully on board with this new trend.

Alas.  My west coast ears were not adapted to Holly’s southern accent.  As I discovered several slides later when it was obvious she was talking about meadow gardens.

Oh well.

Does native matter?

We’ve had lots of lively discussion on my post regarding the Mark Davis et al. comment in Nature on natives and exotics. I have been traveling and otherwise occupied and have not had a chance to comment so I feel a little like the kid that kicked the anthill and then ran away. Fortunately, Holly was gracious enough to forego her post today (I promise to return the favor, Holly!) so I can chime back in.

Obviously there are lots of layers to the debate but one of the main items in the discussion is whether there is an inherent ecological advantage in planting natives over exotics.  At this point the focus always seems to shift to herbivory and the question of whether native insects will eat non-native plants.  There are certainly examples each way; some insects are generalists while others are highly specific.  More importantly, however, plants fill many other roles in the environment beyond serving as food for insects.   Moreover, species composition is just one aspect of diversity.  The ecological function of landscape is also determined by how we manage other factors such as structural diversity and age class distributions.  In his book “Bringing Nature Home” Doug Tallamy shows a picture of a bland, sprawling suburban landscape ( p. 24) and notes “this highly simplified community is made up of a few species of alien ornamental plants that provide neither food nor shelter for wildlife.”  OK, I’ll buy that.  But would the situation change if the blue grass was changed to a native grass kept mowed to 2” and the two widely spaced shade trees were changed to natives?  Doubtful.   The structural complexity; that is, the number and arrangement of grasses, annuals, shrubs, and trees, is likely a bigger driver of ecosystem function than whether the plants are native or exotic.

In his thoughtful comments on the blog post Vincent Vizachero sums up, “I stand by my view that the general heuristic of favoring native plants over alien plants is better than the alternative of not caring about origin at all.”   I can buy that as well, but with the caveat that other factors are equal.  The rub, of course, is that other factors are rarely equal.  And I suppose this is where the pragmatic approach discussed by Davis et al.  resonates with me.  In my position I do a lot of programming on trees for urban and community forests.  I go through a list of criteria to consider for tree selection.  Here are some of the key factors I usually discuss:

Adaptation There is no argument that there are well-documented environmental, economic and social benefits to trees in urban and suburban areas.   But in order to fulfill these roles trees must be able to survive where they are planted.  This means being adapted to abiotic and biotic environmental conditions which are often adverse.  In this region of the country there are some native trees that fit the ‘tough trees for tough places’ bill, such as swamp white oak, bur oak, and honey locust.  Many other natives, especially understory species, are much more difficult to site.

This street planting in Lansing alternated green ash and Norway maple.  

Available space This seems like a no-brainer, but it’s amazing how often this gets overlooked and we end up with too much tree and too little space.  Again, we have some great small native trees; Carpinus, redbud, striped maple.  But these can be limited in their site adaptability.

Ash stumps

Diversity  In Michigan some communities have lost 30% of their tree cover to the emerald ash borer.  Have we learned our lesson about improving species diversity?  Not really.  But we need to keep trying.  Exotic pests are here and here to stay.  Does anyone believe that global trade will decrease in the near future?  Does anyone believe that there will be quantum leap in our ability to detect and intercept hitch-hiking pests?  In order to continue to accrue the benefits of urban and community forests we need to continue to diversify our portfolio; this includes a mix of natives and exotics.  I doubt there will ever be sufficient data to prove one way other, but it seems reasonable to me that an urban and community forest balanced among 20-25 native and exotic species will be better able to withstand the slings and arrows of weather and pests better than one made up of 8-10 natives.

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.”