Bert Cregg

Cold enough for ya?

Like many people we spent the past couple days digging out from the massive snowstorm that swept across a large swath of the country. This was definitely a made-for-TV-weather event as national and local TV weatherfolks took up their positions and gave us breathless live-remotes of the “Blizzard of 2011”.

40 mph wind + 1 little crack = a barn full of snow.

Almost as predictable as video footage of snow-ploughs on the streets and locals snow-blowing sidewalks; climate change skeptics are using the recent round of winter weather as proof that global warming is a hoax and that there’s really nothing to worry about except the economics of ‘cap and trade’. Just google “climate change skeptics blizzard” and you’ll get the idea.

Bob and Quincy were unfazed by the sub-zero wind-chills.

The problem, of course, is that climate patterns don’t move in a strictly linear trajectory and looking at one extreme event doesn’t prove anything one way or the other. Even looking a few years time sequence may not present the full picture. Deroy Murdock used the illustration below to argue in the National Review Online that there is no link between rising CO2 and increasing temperatures.

But looking at a broader timescale tells a different story. While there are year to year fluctuations a clearer association between rising CO2 and global temperature begins to emerge.

The figure above was taken from an article by Stamhoff et al. 2007, “Recent Climate Observations Compared to Projections” (Science 316 (4): 709). The dashed lines represent the ranges predicted by a major climate model starting in 1990 – the solid line represents what actually happened. As shown in the figure, climate models have been fairly accurate overall and, if anything, have been conservative in predicting climate change; especially with regard to changes in sea level.

So where am I going with this? There are certainly enough climate change debate/Al Gore bashing blogs out there to go around and I don’t want to devolve entirely into that debate, but the simplistic ‘exception proves the rule’ mentality of the skeptics gets a little tiresome. I remember hearing my first talk on global warming at a forest biology conference in the mid-1980’s. The main point that stuck with me then was that increasing global CO2 would not necessarily result in warming every year but that we would see an increase in the frequency and severity of extreme climatic events; droughts, hurricanes, floods, and yes, even blizzards. Even some of the earliest discussions on climate change in the early 1980’s (e.g., Manabe and Stoufer 1980) recognized complex feedbacks in the global climate system that would result in some regions getting wetter while others suffered drought. So while the skeptics may use this weeks’ blizzard as evidence against climate change, increasing frequency of severe weather actually argues for it.

A few other climate facts to ponder:

-Global CO2 is increasing and continues to increase (see top panel in figure above).

– Globally, 12 of the 13 warmest years on record have occurred since 1995.

-Intensity of hurricanes and cyclones is increasing (Webster et al., 2005). While Fox and Friends were happily using the Blizzard of 2011 to debunk climate change; did they notice the most powerful cyclone on record was slamming into Australia?

-Frequency and severity of droughts is increasing worldwide (Burke and Brown, 2006).

-Glaciers are disappearing. If you want to go to Glacier National Park and actually see a glacier, you need to hurry. In 1850 there were 150 glaciers in the park. Today there are 25 and they will likely be gone in 10 years.

Insects and Fertilization

Linda got a few comments and questions on her post a couple of weeks ago on fertilization and insect resistance. This is an issue I’ve been peripherally involved with over the years so I wanted to share a few thoughts. First, the relationship between plant nutrition and insect resistance is extremely complex. We often have difficulty predicting how a plant is going to respond to fertilization, let alone predict how an insect is going to respond to how the plant responded. I haven’t kept up but Koricheva (2002) reported over a dozen different theories have been proposed to explain insect response to plant nutrition. One of the factors that makes it difficult to generalize about plant/insect interactions is that various insects feed on different plant parts in different ways; some are leaf feeders, some suck sap, some bore into wood, some feed on seeds or cones. How an insect feeds can affect its response. To stick with an illustration I’m more familiar with, we can look at insect response to plant drought stress. Bark beetles are widely known to key in and attack pines and other conifers under drought stress but pine tip moths prefer succulent buds and new growth and are more likely to attack well watered trees. It’s not unreasonable to think there are similar differences with nutrition.

Nevertheless, as noted above, there have been attempts to come up with general theories on the effect of plant nutrition on insect resistance. One of the most widely cited is the Growth-differential balance theory proposed by Dan Herms and Bill Mattson (“The dilemma of plants: to grow or defend.” Q. Rev. Biol. 67: 283-335). A quick check on Google Scholar indicated this paper has been cited by over 1,400 other papers, which is an astounding number and speaks to its influence. The basic premise of the theory, as suggested by the title of the paper, is that plants make a trade-off between allocating carbohydrates for growth or allocating carbohydrates for secondary defense compounds. Dan Herms subsequently applied the theory in synthesizing the literature on woody ornamentals in his 2002 paper, “Effects of Fertilization on Insect Resistance of Woody Ornamental Plants: Reassessing an Entrenched Paradigm.” (Environmental Entomology 31(6):923-933.). I have heard some arborists and others use this paper to argue that we shouldn’t fertilize landscape trees at all. The problem is they oversimplifying the theory – which is understandable, this is pretty heady stuff. They get the ‘trade-off’ idea; if plants grow fast they produce lots of yummy stuff for bugs. But what is often overlooked – even though Herms makes a point to say it – is that when nutrition or other plant resources are low; there is no trade-off.

This figure from Herms and Mattson illustrates the idea. If nutrients are deficient and we fertilize a plant the plant may increase growth and secondary compounds; it’s not always an either/or situation. The bottom-line remains the same; nutrient deficient plants can benefit from fertilization or correcting the factors (e.g., alkaline pH) that made them deficient in the first place.

Koricheva, J. 2002. The Carbon-Nutrient Balance Hypothesis Is Dead; Long Live the Carbon-Nutrient Balance Hypothesis? Oikos 98 (3): 537-539

Warning: This blog may be hazardous to your health

Following up on Jeff’s post last week regarding blue spruce. Jeff noted, and several posters agreed, that even though blue spruce will eventually have a host of pest problems, for the first 10 years or so it’s a darn good looking landscape conifer. Jeff went on to draw the analogy that choosing a blue spruce is like choosing sexy sports car or gas guzzler over a boring, high MPG sedan. To a certain extent the libertarian in me agrees. If I want to plant a blue spruce in my Michigan backyard or buy a Nissan Titan to commute back and forth to work , by Gawd, that’s nobody’s business but my own. Of course the difference in these situations is that I have EPA reporting to tell me the Titan only gets 12 MPG in the city; for the spruce, people like Jeff, me, and our highly intelligent readers know what we’re getting into from experience and training. But what about the public at large? Maybe what we need are government warning labels for plants. We have them for cigarettes: “Warning: Smoking Causes Lung Cancer, Heart Disease, Emphysema, And May Complicate Pregnancy”, though the European warning, “Smoking kills” is more direct and to the point. We also have warnings for side effects of prescription medications; “may cause nausea, vomiting, headache, hearing loss, oily discharge, an erection lasing four hours, and thoughts of suicide”. Think I’ll take my chances with the disease, thank you.

So what kind of labels do plants need?

Blue spruce: Warning this plant will look great in your yard for 10 years and then fall apart when it becomes a magnet for gall adelgid and loses half its limbs to cyctospora.

Eastern white pine: Caution: This little guy looks like a cute little Christmas right now but in 10 years it can devour your house.

Silver maple: Warning: Don’t blame us when this tree comes crashing though your house during windstorm.

Sweetgum: Caution: Be sure to retain a good attorney for when your neighbors start tripping over gumballs on the sidewalk.

That’s a start. What plants do you think need warning labels?

Landscape conifers: The Good, the Bad, and the Underused

This week is our annual Great Lakes Trade Expo, the main trade show and education venue for Michigan nursery and landscape industry. One of my talks was for the Arboriculture track on landscapes conifers. The theme this year was “The Good, the Bad, and the Underused.” Hey, you try giving a dozen talks a year for 10 years and see if you can come up with an original title!

The selections were based the following, admittedly subjective, criteria.

The Good: These are the all-around good guys. Conifers that are well-adapted, good growers with good form and few pest problems.

The Bad: The problem children of the conifer world. Pest magnets, spoiled prima donnas, or incessantly overused.

The Underused: Trees that have the virtues of ‘The Good’ but that tend not to attract attention.

Here are three of my selections for each of the categories. I’m interested in nominees from other sections of the country and the world.

The Good:

Eastern white pine Pinus strobus This one flirts with the overused designation but I’ll give it a nod since it’s the state tree of Michigan and figured prominently in the state’s history when Michigan was the lumbering capital of the US in the late 19^th century. A fast growing tree that improves with age.

Eastern hemlock Tsuga canadensis The answer to the age-old question, ‘What conifer to you recommend for shade?’ A little finicky on site, prefers moist but well-drained – who doesn’t. But a great elegant looking tree. The main down side is the specter of hemlock wooly adelgid looming to our south.

Alaska false cypress Chamaecyparis nootkatensis (Xanthocyparis nootkatensis). Lot of confusion over the nomenclature but no question this is a great landscape tree. Graceful, weeping habit; good growth rate; and few pests in this area (knock on wood).

The Bad.

Scots pine Pinus sylvestris Is there a pest that doesn’t affect this tree? Our Forest Entomologist, Dr. McCullough, had a grad student count up all the pests that affect Scots pine and they lost count after 30. Borers, tip moths, needlecasts… the hits keep coming. The problems are exacerbated around here because of abandoned Christmas tree plantations that serve as insect breeding grounds and fungal infection courts.

Austrian pine Pinus nigra Austrian pine is a frustrating tree. In some respects it is the perfect conifer for our region. A great looking tree with dark green needles. Good growth rate, cold hardy, drought hardy, tolerates road salt. Everything you could want in a tree and then some. Then the trees get about 15 years old and the wheels fall off. Diplodia tip blight, dothistoma needle blight… Austrian pine is the ugly duckling in reverse; looks great when young and then, blechh…

Colorado blue spruce Picea pungens The tree everyone loves to hate, yet we keep planting it. I suppose it’s the allure of the blue that people can’t resist. It’s like that bad boyfriend; you know he’ll do you wrong but… He’ll lure you in with those baby blues then start hanging out with those low-life Cooley adelgids, then hook up with rhizosphaera needlecast. And by the time the cytospora cankers start hanging out you know this relationship is going nowhere.

The underused

Swiss stone pine Pinus cembra Renowned conifer aficionado ‘Chub’ Harper used to remark, “I never met a cembra I didn’t like.” Cembras are great trees, good growers with consistently good form. Underused but worth looking for.

Korean fir Abies koreana I wrote about Korean when in discussion alternative Christmas trees but it also makes a good landscape tree. In our area we can expect about 1’ of height growth per year. Symmetrical form; short needles with silvery undersides, and conspicuous cones. Lot to like about Korean fir.

Dawn redwood Metasequoia glyptostaboides A fast-growing deciduous conifer with wonderful pyramidal form. Dawn redwood is also an interesting botanical story. Only known to science from fossil records, an isolated population was discovered in China in the 1940’s. Seed were imported into the U.S. and the tree has been found to be broadly adapted.

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New Year’s Prediction: Invasive Fire Continues to Burn

Happy New Year! I hope everyone had restful and enjoyable holidays. In addition to looking back over the year that just past, a common New Year’s tradition is to make predictions for the coming year. Without going too far out on a limb, one of my predictions for the upcoming year is that the debate over invasive plants will continue to intensify, especially as it relates to Landscape Horticulture. Along these lines, a couple of recent articles by Gregorio Gavier-Pizarro and his colleagues at the University of Wisconsin and the USDA Forest Service caught my eye.

In both studies; “Housing is positively associated with invasive exotic plant species richness in New England, USA” (Ecological Applications 20:7, 1913-1925) and “Rural housing is related to plant invasions in forests of southern Wisconsin, USA” (Landscape Ecology 25:10, 1505-1518), the investigators conducted on-ground assessments of species richness and density of commonly listed invasive plants (e.g., Japanese barberry, Autumn olive, Honeysuckle, Common buckthorn, Multiflora rose) in conjunction with spatial analysis of remote sensing data to examine patterns of invasive spread in the urban/wildland interface. As one would expect, the presence and species richness of the invasives increased with development. An important ‘take home’ message, however, is that disturbance associated with rural housing development and the creation of edges appears to be the biggest driver of invasive species encroachment. That is, land clearing, road-building and other development activities create habitats that are more susceptible colonization – a condition referred to as ‘invasibility’. So whether a particular homeowner plants natives or non-invasive exotics they may still contribute to the expansion of invasive exotic plants in their region by increasing its invisibility.

The other thing that makes this work and related studies significant is that I think we will see a continued shift in the efforts to curtail the expansion of invasive exotic plants. In particular, rural housing development and associated landscape practices will become and increasingly intense front-line in the invasive battle.

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Happy Holidays!

Relaxing at the in-laws in Ohio for the long Christmas weekend. Hope all of our blog readers are having a enjoyable holidays. In other words, I hope you didn’t have to fly anywhere over this Christmas weekend!

I’ve been catching up on some reading including recent articles on invasive alien plants that should be of interest to our readers. I’ll share some thoughts when I get back on schedule next week. In the meantime there’s still another football game to watch this evening and another plate of my mother-in-law’s cookies that need some attention.

Have a safe and happy New Year!

What fir?

OK, it’s the middle of December so I get to indulge my passion for Christmas trees. One of the most interesting projects I’ve gotten to work on during my time at Michigan State is a study to look at alternative species of firs (Abies spp) for Christmas trees and well as for landscape conifers. Firs are fascinating trees that are distributed throughout temperate regions of the northern hemisphere. There are about 50 species, many of which are important for timber, landscaping or Christmas trees.

For those of you that put off your Christmas tree shopping until the end (or want to start thinking about next year’s tree) here are three trees to keep an eye out for.

Korean fir Abies koreana We have several growers in Michigan that are now growing Korean fir. It has relatively short needles that have a bottle-brush arrangement on the stem. The color is often described as dark green, but I’d say the needles tend more to a true green or Kelly green with a silvery underside.

Concolor fir also makes a great landscape conifer

Conolor fir Abies concolor I grew up in the Northwest so I always knew this tree as white fir until I moved to the Midwest. In any case, it’s a great tree. Long, soft-blue needles. Depending on the seed source they can be as blue as a blue spruce. The main draw-back here in Michigan is that concolor tend to break bud early, which makes them susceptible to frost damage in the spring. Their citrus-like scent is hard to beat.

Danish growers compete for the best Nordmann fir in the “Fight for the Golden star” at their annual tree fair.

Nordmann fir Abies nordmanniana Denmark is the leading producer of Christmas trees in Europe and Nordmann fir is their principle species. The Danes like Nordmann because of its deep, dark green color and natural form and symmetry. Europeans don’t like their Christmas trees sheared so they rely heavily on genetics and selection to find trees that naturally have good form. We’re starting to see more Nordmann in the US, both here in the Midwest and in the Northwest. Growers complain that the trees are slow-growing to start but I think some US consumers are looking for a more open, natural-looking tree and Nordmann can fill this niche.

Saving your ash

My earlier post regarding plans to replace the monoculture of ash trees at the Gateway Arch Monument in St. Louis, MO with a monoculture of Lindens prompted a question about options for treating ash trees for emerald ash borer. This is a complex topic so I wanted make sure I had time and space to respond completely.

First, the best and most current source of information regarding treatments for EAB is the Multi-state bulletin “Insecticide Options for Protecting Ash Trees from Emerald Ash Borer” which is available as a full-color .pdf on the EmeraldAshBorer.info website. Anyone who lives in or near EAB-affected areas and is considering treating their ash trees should take the time to download and read this bulletin.

Here are some key points to consider if you want to save you ash:

It is possible to protect ash trees from EAB with insecticides. There are several examples in and around the original core infestation area in Detroit where arborists have successfully protected trees since EAB first was identified in 2002. There are two general options; protective cover sprays and systemic applications. For most trees, protective cover applications will require professional application with specialized high-pressure spray equipment. Most systemic application will also need to be applied by professional applicators, except for small trees that can be treated with soil drenches of systemic insecticide. To date, the most effective systemic product is emamectin benzoate, sold under the trade name TREE-äge. In various tests, emamectin has shown the highest level of control among products tested and is also the only product that consistently provides more than one year of control. Imidacloprid is also effective as a systemic but will need to be re-applied annually for the best level of control.

The likelihood of successfully treating an ash tree declines rapidly once trees begin to show noticeable crown-die-back. In certain cases, researchers have been able to save EAB-infested trees showing some crown die-back, but once 50% of the crown is affected the tree is likely a goner.

Once started, treatments will need to continue in perpetuity. To me, this is the biggest factor homeowners need to consider if they’re thinking about treating their ash trees. To the best of our knowledge, EAB is here to stay. EAB populations may begin to decline once most of the ash trees in a region have been wiped out, but trees in woodlots and forests that have been killed will continue to sprout, providing host material to maintain an endemic population of beetles for the foreseeable future. Systemic applications can provide control but the products will need to be re-applied every year (imidacloprid) or every other year (emamectin) to be effective.

Effectively treating trees larger than 4” in diameter will require applications by a certified pesticide applicator and may cost several hundred dollars per tree. Homeowners need to carefully consider the cost of on-going treatments versus removal and replacement.

Mention of trade names does not imply in endorsement. Read and follow label directions when applying pesticides.

Maybe common sense isn’t so common after all

I noted in my Sept. 22, 2009 post on the threat posed to ash trees in the Midwest by the emerald ash borer (EAB), and included photos of the famous grove of 500 ash trees surrounding the Gateway Arch in St. Louis. I was in St. Louis that summer for the ASHS meeting and saw that the National Park Service was planting trees from a variety of species around the monument. I assumed at the time that the Park Service was preparing for the eventual loss of the ashes to EAB. Boy, did I get a wrong number.

Last week my former grad student, Sara Tanis, alerted me to an article from the St. Louis Post-Dispatch. The Post-Dispatch reports that with the destruction of the grove of ash trees looming, the National Park Service has contracted with a Los Angeles-based landscape architecture firm to replace the monoculture of ash trees with, I am not making this up, a monoculture of linden trees. I’ve heard that the definition of insanity is to keep doing the same thing and hoping for a different result. Apparently the landscape architects that are drawing up these plans have never seen what Japanese beetles do linden trees. Oh, that’s right; the L.A.’s are in L.A.

The article is available on-line if you can stomach it. http://www.stltoday.com/news/local/metro/article_1e65095d-96ae-507a-acda-574d9f54a73b.html

On the bright side, since this is a Federal project it will likely move forward at glacial speed and will require public input. Here’s hoping the Park Service gets an earful and common sense will prevail.

Not your father’s extension service

We recently received a question on one of my old posts (Dec. 12, 2009) from a blog reader in Iran (yes, Iran) regarding agricultural extension and asking what’s new in how we disseminate science-based information. There’s no doubt that things have evolved in agricultrual extension over the years. There’s an old joke: Guy walks into a county extension office and the agent is sitting behind his desk, crying. The visitor asks, “What’s the matter?” Agent replies, “My farmer died.”

Hey, I said it was an old joke, I didn’t say it was a funny one. Point is, the days of field extension agents or campus-based extension personnel going out and holding a farmer’s hand are long gone. While some may still think of dim-witted Hank Kimball on “Green Acres” when they think of extension (go to http://www.hulu.com/watch/140842/green-acres-my-husband-the-rooster-renter if you miss the reference), most university extension is going increasingly high tech. I’m sure each on my colleagues can provide several examples of recent extension innovations in there area. I’ll provide one that we have just launched here at Michigan State.

Obviously the single biggest tool we have for outreach and extension is the internet. Recently, Dr. Pascal Nzokou, one of the lead members of our Christmas tree extension team launched the MSU Christmas Tree Channel on youtube http://www.youtube.com/user/MSUChristmasTrees

On the Christmas tree channel members of our extension team provide short (1 ½ – 4 minute) videos on various aspects of production: site selection, species selection, pest management, irrigation, nutrition.

There are several advantages of using youtube for these types of videos. First, uploading the videos is easy and straightforward. We had a professional shoot the videos and do the editing but anyone with a digital video camera can shoot videos and load them on to youtube. For short videos it’s easy to upload videos for viewing even at HD resolution eliminating the ‘Invisibale Gardener expereince’. Once the video is loaded you can send the link out to people you think will be interested or include the link on your website. People may also find your video using the search feature depending on the information you include in the description. Lastly, most people that use the web regularly are used to searching and viewing on youtube so there’s high consumer acceptance.

Published: 11/22/2010 2:21 PM

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