The Garden Professors™ – Page 118 – Advancing the science of gardening and other stuff since 2009

Do Organophosphates cause ADHD?

Ever since Monday’s post I’ve been preoccupied thinking about that article which was mentioned in the comments section by Daniel http://www.cnn.com/2010/HEALTH/05/17/pesticides.adhd/index.html?iref=allsearch . This article basically summarized a study that seemed to show that ADHD in children was related to exposure to organophosphate insecticides.

Articles like this appear all of the time in mainstream media and they scare the bejezus out of us because, after reading them, we end up thinking “Holy crap! We’re killing ourselves and ruining our society with these insane chemicals!” Most of the time, however, this just isn’t the case. Look, if everything that the papers reported about the negative effects of pesticides and other chemicals was true we’d all have cancer, mental illness, or we’d just be dead.

After the above you’re probably telling yourself that I’m some kind of maniacal chemical apologist. Maybe I am, but I don’t think so. I’ve spent a lot of time reading the actual articles from which these media pieces are written and I like to think I have a relatively balanced view of these chemicals – maybe I’m deluding myself though – I’ve been known to do that on occasion. In any regard, what I’m going to do with this blog post is to take a look at the media article and let you know some of the questions that I want answered before I get very concerned about the research, and by answered I mean answered by the scientific article from which the media piece was derived. Now, to be fair, I have not read the actual scientific article from which this media piece was derived. It isn’t online as I’m writing this (at least nowhere that I can find it), though I have no doubt that it will be soon. I suppose that I could have waited to write this until it came out, in fact I considered that idea carefully, but instead I thought that I would tell you about the things that I’m wondering about the article; In other words, the things that I’ll be looking for when I finally get to read it. Media people want POW! Scientists want to know what’s actually going on.

Before we begin I should tell you that I’m no fan of organophosphates. They include a wide range of chemicals (though they are, obviously, all related in that they’re organic chemicals with phosphorus), some worse than others – from the relatively tame orthene and malathion to the scary-as-hell disulfoton (aka disyston). Right now, as an extension specialist who works with growers, I can tell you that organophosphate chemicals are, in general, not a preferred choice for most growers simply because there are so many safer and more effective choices out there. My feelings about organophosphates can best be summed up by what I wrote in my book The Truth About Organic Gardening “[Organophosphates] are an old class of insecticides that has served its purpose and for the most part should probably go the way of the dodo, with the possible exception of orthene and one or two others.”

So here we go, the things that I will be looking for when I read the actual scientific article:

1. What’s the confidence interval? In the media article it was stated that children with higher levels of organophosphates were about two times more likely to have ADHD, but no confidence interval was given. In epidemiological studies such as this the likelihood of a given outcome is usually expressed as an odds ratio. In this case the odds ratio that a child would develop ADHD given a high level of organophosphate exposure would be about 2 (because it would be 2 times as likely that a child would develop ADHD as it would be if the child weren’t exposed to the organophosphates). But in a scientific article the odds ratio will always be coupled with a confidence interval. A confidence interval tells you how confident you are in your odds ratio. If you’re very confident then you’ll have a narrow confidence interval – maybe 1.8-2.2 — which means that it is 95% certain that the odds ratio is between 1.8 and 2.2 (the 2.0 odds ratio is basically just the most likely point on the confidence interval for the odds ratio to sit. It’s kind of like, but not exactly the same as, an average). For an epidemiological study that’s darn good. If that’s the confidence interval present in the article then I’ll be impressed. What we might find though is a confidence interval of something like 0.2 to 22. That stinks and you’re deluding yourself if you think that a confidence interval like this “proves” anything – unfortunately I have seen plenty of media articles use research with confidence intervals such as this because of the POW! factor. They ignore the confidence interval and just look at the odds ratio. My guess is that this article has something in between the two confidence intervals which I listed above – we’ll see.

2. I want to know how often urine was sampled.
Organophosphates move through the body very quickly. In fact, I was recently reading a paper which showed that you can’t predict from one test time to the next what organophosphate readings will be because there’s so little consistency. If you’re exposed to an organophosphate one day you may test high that day, but two days later you’ll be testing low again, so, I want to know if a single sample was done – which I would consider to be almost useless in terms of telling us actual organophosphate exposure – or if multiple samples were taken over time which I would consider to be much more useful.

3. Did the organophosphate really come from food? The implication that these organophosphates which, in theory, contributed to the onset of ADHD came from food bugs me. I want to see if the author actually draws this conclusion in the paper or if it was made up by the media. There are lots of places that organophosphates are and have been used, the singling out of fruits, vegetables, or any food seems ridiculous to me. The author of the media article points out that organophosphates are not used around homes much – but that really isn’t the case and it certainly wasn’t the case just a few short years ago. There are still plenty of organophosphates being used quite regularly around homes. I just did a search for orthene and malathion and found that I could buy them quite easily online. Diazinon and chlorpyrifos are two others that shouldn’t be used by homeowners but which I know of people using – sometimes in heavily trafficked areas.

4. I’d like to know about how the other potential contributors to ADHD were controlled. There are other things that have been correlated with ADHD, how were these controlled so we know they weren’t the cause of the ADHD measured in this experiment? For example, abused or neglected children seem to have a higher rate of ADHD, how was this taken into account in the study? Was it taken into account? A theory would be (and I’m totally making this up) what if abused children are fed more food with higher rates of organophosphates while non-abused children are fed more organic food. Then the results would show that the neglected kids had higher ADHD and higher organophosphates – but was it the poor parenting or the organophosphates which caused the ADHD?

So, those are the four questions that I’ll be asking right off – and there are more that I’ll think of once I actually read the article. All of these questions don’t mean that I think the article is bad though – regardless of what their answers are. This research was probably well conducted and will enlighten scientists and lead to new avenues of research. But, I’m willing to bet that the POW! from the media article (ADHD is caused by eating organophosphates on food) isn’t quite as powerful when the whole article is read with a more critical eye.

Yet another fine product

As a member of the GWA (Garden Writers Association), I routinely get emails about new garden products. Here’s one I received this week:

“I thought your readers or listeners might be interested in learning of a new way to protect their plants without using pesticides. Moisturin, which contains no toxic ingredients, is sprayed on plants to form a clear flexible barrier strong enough to lock out both insects and airborne plant disease. Moisturin is inexpensive, easy to use and extremely effective. I would like to send you some at no charge for your own trial. If your satisfied with it performance I hope you will pass it s benefits onto the people who trust your opinion.”

It turns out that Moisturin is simply a repackaged antitranspirant. Briefly, these spray-on barriers prevent water loss physically (by covering stomata) or physiologically (by closing stomata). Interfering with stomatal function both reduces carbon dioxide uptake and water movement within the plant. You can read more about antitranspirants here.

But do antitranspirants have an effect on diseases or insects? Research indicates that while antitranspirants may reduce insect attack, their efficacy against diseases is less clear. They also show a clear negative impact on the plants they supposedly protect, to the extent they’ve even been tested as a form of weed control.

The best way to reduce pest and disease problems in garden and landscape plants is to keep them healthy. Reducing their ability to function normally by clogging their stomata will do exactly the opposite.

Building a Better Container, Part Deux: The Ellepot

I enjoyed Jeff’s post on the RootTrapper and thought I’d share another interesting and [relatively] new development in the world of greenhouse growing containers.

Take a tube full of growing media, wrap a paper sleeve around it, and voila – the Ellepot!

It’s bottomless, root permeable, and degradable. Each Ellepot sits in its own cell in a re-usable tray. The great aeration and drainage makes for a happy, healthy root system. Another plus is that after transplanting, there are no pots or packs to throw away

I’d say the bulk of Elle Pots are utilized at the propagation end of things – starting seeds and rooting vegetative cuttings – either for greenhouses to “grow on” themselves or as plug/liner products sold to finishing growers (see student Paul Hutcheson holding a geranium liner above).

Ella and Ojvind Ellegard of Denmark developed the system in the early 1990’s. Popular with growers in Europe, they’ve made their way to North America. Growers can buy in Ellepots by the pallet from various sources, or can invest in the equipment to make them

Wrap it up, I’ll take it…an Ellepot machine at Battlefield Farms, Rapidan, Virginia.

Sizes run from 15 mm (288 cells per 20” x 10” tray) up to 120 mm – equivalent to a 4” pot, perfect for bedding plants. Landscapers love them if they can find them – less waste from installation sites.

Petunia in an Ellepot. That’s Marc Verdel, head grower at Battlefield Farms.

As far as retail goes, I’m not sure if any market research has been done as to consumer preferences for this “pot-less” system. It’s a slight challenge for a shopper to pick one of this and two of that and transport them – you need some kind of carry tray. Anyone out there experienced with Ellepots (grower or gardener)?

Visiting Professor guest post: Organic foods

There are lots of reasons consumers give for buying organic foods, but a few reasons are very common. Among them is the notion that organic foods are better for you. Really? Are organic fruits and veggies better for you? Depends on what you mean by ‘better for you’. But as far as we know, the answer is probably ‘no’, especially if you’re buying organic fruits and veggies (F&V) at the store. It might seem crazy, but there’s no good evidence to support the notion that you will be more healthy by shopping for organic F&V. There are some complicated reasons for this, and some areas we aren’t quite sure about yet, but I’ll try to explain.

If ‘better for you’ means ‘fewer pesticide residues,’ you’re right. But if you think ‘fewer pesticide residues’ means ‘better for you,’ that gets murky. Why do we apply pesticides? We do it to protect our food from pests and diseases. It’s cheaper and more productive than destroying blight-infected tomatoes, individually wrapping apples in a protective barrier, or throwing away heads of cabbage with worms. But why do those things matter? It turns out we’re just consumers. Two big things we look for when buying F&V are appearance and cost. If a person has a choice between a spotty, more expensive apple and a uniformly bright and shiny lower-cost apple, he’ll probably choose the latter. And which would be better, buying 2 heads of cauliflower because it’s pretty and low-cost (conventional), or buying one head because it has a slight cosmetic defect and costs a little more (organic)? You guessed it; in terms of your health, it’s more likely that 2 heads are better than 1. If that isn’t complicated enough, consider that there are no good long-term human studies concerning the health effects of pesticide residues ingested from food. There’s no evidence that eating conventional F&V, even with the elevated risk of consuming more pesticide residues, is worse for you than eating organic F&V. But there is evidence that eating more F&V is better for you than eating less. So why eat less?

Some of the best health care in Minnesota comes from the Mayo Clinic. What? Who cares about the Mayo Clinic? In Minnesota, we worship the Mayo Clinic. [undeserved pride] They represent some of the finest health care in the country [/undeserved pride]. And what does the Mayo Clinic have to say about pesticides on our food? “Most experts agree…that the amount of pesticides found on fruits and vegetables poses a very small health risk.”

But what about nutrients—don’t organic foods have more nutrients or something good in them? Maybe they do have fewer nitrates (which may be bad for you, especially if you’re too young to read this), but that really depends on how the specific growers use fertilizers. Maybe some organic produce tends to have more vitamin C, but that can vary too. And even if the organic tomato you’re eating has more vitamin C than the conventional tomato you passed up, is that physiologically relevant? Does it matter to your body? We don’t have any good evidence that it is.

Why am I being so down on organics? Mostly because I like to play devil’s advocate. I buy a lot of organic F&V. There are some reasons to buy organics that may be more legitimate than “it’s better for me”. Sadly, research seems to indicate that I buy organic F&V to make myself feel good for buying it, not because it’s actually better for me. But in general, eating healthy means eating more fruits and vegetables.

Charlie Rohwer is a horticultural scientist at the University of Minnesota Southern Research and Outreach Center. He has an MS from Michigan State University and a PhD from the U of M. He currently studies vegetables and things that make them good for you.

Short tree syndrome solved!

Good answers from Kenny S., Jimbo, Joe Schalk and Diana! You were all skirting about the phenomenon of thigmomorphogenesis – or touch-induced change (also discussed in Jeff’s post of January 7. The tests in the GP’s class are cumulative!). In this case, the touch is wind. Edge trees (or corn stalks) are more exposed and receive more wind, resulting in stunted heights and increased trunk diameter (you can’t see this last characteristic in the Friday photo). Trees in the middle of the stand aren’t exposed to wind buffeting and put their resources into increased height. Similar stunting and thickening can be seen in urban plantings along the edges of sidewalks or anywhere people or animals routinely walk.

I spent my grade school years in a 1950’s housing development that had been Douglas fir (Pseudotsuga menziesii) forest. The developers left many of the trees standing, and our backyard was full of tall, skinny and isolated Douglas firs. When the Columbus Day storm (an extratropical cyclone, of all things) hit the Pacific NW in 1962, seven of these trees came down (none hit our house, fortunately).

Now of course a cyclone will take down many trees, regardless of their location…but this continued practice of leaving trees standing alone during development often results in blowdown or breakage of these now unprotected trees.

Friday quiz time

Here’s an interesting phenomenon you can see in any group of plants – it’s what we call the edge effect:

Today’s question: why are the trees in the foreground so much shorter than those just a few feet farther from the edge? Answer on Monday!

Building a Better Container

As most of you know, roots circling around a container isn’t considered a good thing. And so people try various things to control circling roots. One of the more creative horticultural minds out there, Carl Whitcomb, a guy why basically got sick of academia and went into private industry (and, as far as I can tell, loathes peer review and the whole process of publication), decided to see what he could do about making containers that don’t encourage circling roots. He came up with a number of designs, but my favorite is the RootTrapper. The container is made of a flexible cloth which roots get lodged in, preventing them from circling. Not that I’ve never seen a circling root in a RootTrapper, it’s just that these circling roots are extremely rare.

A row of elms in RootTrappers

A cut open RootTrapper

This is one of those innovative products that really works and it surprises me that so few people use this growing system. Yes, it’s a bit more expensive than standard containers, and yes, it does take a little more effort to take the tree out of this container than a smooth sided one. But man, I’ve never seen a better root system come out of a container than those which you get out of these.

Permaculture – more concerns

One of the gardening topics I’ve researched extensively is the use of landscape mulches. (You can read a literature review I did a few years ago here.) So I was more than a little frustrated to see one of the worst mulching techniques – sheet mulching – extolled in the book Gaia’s Garden (pp. 85-90).

Sheet mulches, like newspaper and cardboard, can be used successfully as a temporary weed control measure (i.e. a few weeks before planting a vegetable garden). Long term, they are not a sustainable choice and often cause more damage to the system than the presence of weeds.

The two-dimensional structure of sheet mulches functions as a barrier to not only weeds but to the movement of air and water as well. While this may initially increase soil water retention since evaporation is reduced, over the long term they will create soils that are unnaturally dry. This condition is worsened on low-maintenance sites,where neglected sheet mulches easily dry out, causing rainfall or irrigation water to sheet away rather than percolate through.

In contrast, wet, poorly drained soils will become even more so as layers of moist paper or cardboard restrict evaporation and aeration. Moreover, this condition encourages root growth on top of the sheet mulch, which can injure desirable plants when and if the sheet mulch is removed.

There are other disadvantages as well. Exposed newspaper and cardboard mulches are easily dislodged by the wind, animals and pedestrians and often provide food for termites and shelter for rodents such as voles. Combined with a somewhat marginal ability to control weeds compared to other organic mulches, sheet mulches are arguably one of the least attractive or effective choices for a sustainable landscape.

Sheet mulching proponents will argue that newspaper and cardboard are only part of the mulch structure – that organic materials such as compost and wood chips need to be added as well. To which I respond – then why bother with the sheet mulch? Why not just use deep layers of coarse organic materials? That’s exactly what forest duff layers consist of. It’s been repeatedly demonstrated that thick layers of coarse organic materials are the best and most natural choices for mulching. (See, for instance, my Ecological Restoration article on using a foot of arborist wood chips to suppress blackberry and enhance native plantings. )

The appeal of sheet mulching is its formulaic structure and logical approach – it’s like making lasagna (the name of yet another nonscientific approach to mulching). Unfortunately, sheet mulching is neither natural nor particularly effective.

Last-Frost-Date Roulette

We all play the game – at least the more impetuous among us do. You sneak a few tender things out into the garden, or on to the patio. When the temperature drops and there’s a frost warning, no problem…just cover them up or bring them in.

Unless you forget.

This WAS a rare and neato Pereskia aculeata ‘Variegata’. Paul W., please send me another…

Before dawn on Monday morning, (May 9) the temperature on our little mountainside dropped below freezing for four hours, going as low as 29.5 F according to our weather station. I had tucked everything back into the greenhouse or up under the eaves…except for the contents of a built-in planter on a far outpost of our deck.

Top o' the frosty mornin' to ya...
Dahlia Mystic Desire, edged in frost at 7:00 a.m., May 10.

NOAA has a handy set of maps that illustrate last dates of “Spring freeze occurrence”. The maps present data averaged between 1951 and 1980.

Walking around the garden last evening with a nice hot cup of martini, I surveyed the damage. Big, juicy-stemmed bleeding hearts that seem so fragile and succulent? Not a speck of injury – but they’ve been up since March. Newly emerged (and really expensive) Asian Jack-in-the-pulpits looked like wet rats. Annuals and tropicals exposed out in the open didn’t stand a chance. Early-to-leaf-out trees can take a beating, too. Japanese maples are notoriously precocious, flinging their fabulous foliage out as much as 45 days prior to last frost here. They’re in pretty good shape now, having acclimated a bit. But for our previous hard frost,15 days ago, we had eight little maples individually draped in white row cover (looked like Halloween).

No longer desirable...
Dahlia Mystic Desire, kaput at 7:00 p.m., May 10.

So why the damage on some and not others? Plants differ in the amount of sugars, proteins, and other compounds that affect the osmotic potential in cells. The lower the content of these compounds, the more likely freeze damage will occur. Young and unacclimated tissue tends to have a higher ratio of water. Like an overfilled water bottle stuck in the freezer, something’s got give as the liquid crystallizes and expands (vast oversimplification, sorry). Cells burst, or are crushed from the freezing of intracellular water, and fluid goes everywhere – hence the limp, dark, water-soaked appearance.

Fog or dew on the plant can delay injury; as external moisture freezes, in gives off heat (an exothermic reaction; one of the amendments to the Laws of Thermodynamics), until all the water is frozen. This is why citrus groves are continually sprayed with water during a freeze event. So it also depends on the duration of the cold; if temperatures just briefly drops below freezing, damage is minimal. Four hours for non-acclimated tissue? See the grim photos for results. Will I wait until May 15 to plant stuff out next year? Absolutely, positively, not. We’re due a no-late-frost spring!

Green mystery disk identified!

Initially I was disappointed that no one answered the question…then Paul W. emailed to say that the post wasn’t accepting comments. We’re not sure why that happened, but Paul and perhaps many of you knew this was part of the flower of Sarracenia flava – the yellow pitcher plant:

I think this is a stunning flower whose floral structure promotes cross-pollination. Insects crawl in between the long yellow petals and the green "umbrella" to enter the flower and reach the pollen:

Before they reach the anthers, however, their backs rub up against the stigma, which are five tiny points at the "spokes" of the umbrella. Pollen already on their backs will be transferred to the stigma before new pollen is gathered, so that the chances of selfing are reduced:

So thanks, Paul, for being so persistant that you emailed me to supply the answer and alert me to the comment fail!