Month: May 2012

I’ve had an on-going discussion – OK, argument – with a fellow faculty member who does research on social dimensions of forestry, including urban forestry.  She contends that we basically know everything we need to know about growing trees in cities and that the real underlying problems in urban and community forestry these days are social issues.  This, of course, means that funding for urban forestry research, what little there is, should be directed at social sciences.  Needless to say, as a tree physiologist, I can point to lots of examples of trees in cities in pitiful conditions and under stress.  To which, my colleague would hasten to ask, “Is it because the urban forester (if the city can afford one) doesn’t know any better or because they don’t have the resources to do anything about it?”  Which is a valid point.  Most of the urban and community foresters I know are dedicated, well-educated, highly professional, and woefully under-staffed.  The Greening of Detroit, a community-based urban forestry non-profit, got its start several years ago because the city could not afford a tree planting program.  The city forestry department dedicated its meager resources to tree trimming; going into triage mode on a 125-year back-log of tree maintenance.  Why would a city plant trees when it can’t even care for the ones it has?

What got me thinking about this was a New York Times article on a rash of tree grate thefts in the city. http://cityroom.blogs.nytimes.com/2012/05/10/if-its-made-of-metal-thieves-increasingly-have-an-eye-for-it/  With the rising price of metal such as iron and copper, thieves are making off with just about anything made of metal including tree grates and man-hole covers.  We can probably start a whole other debate about tree grates and tree pits and whether they are effective, but, in any event, the city forestry department will now have to devote resources to replacing the stolen tree grates and figuring out ways to keep the replacements from disappearing as well.  

I’m not ready to concede that we know everything we need to know about growing trees, but the longer I’m at it, the more I see the need to integrate the biological and the social elements.  We can develop the best tree establishment and tree care protocols in the world but if there no money or no public support to implement them, it’s all for naught.

I’m not going to sugar coat it – I’ve been too cavalier in recommending iron phosphate for slugs and snails. 

A few days ago Erin Harris put a comment in my post about dandelions asking whether those iron phosphate baits you can buy for slugs might also be toxic to earthworms.  The answer is yes – they might.  And not only that, these iron phosphate baits can also be toxic to other animals such as dogs.

How bad might these products be for dogs and earthworms you ask?  I don’t think anyone knows exactly, but to my knowledge this is the most recent paper on the subject.  And here’s an abstract on dog poisonings.

Now, based on the data I’ve seen on poisoning incidents, iron phosphate is less likely to poison your dog than its closest competitor, metaldehyde (though the iron phosphate seems more likely to hurt earthworms than the metaldehyde).  I’m not going to stop recommending iron phosphate – Still, I can’t recommend it quite as freely as I have been in my talks — I need to add some real caveats. 

So then the question is, how did I not know about the potential problems of iron phosphate?  Simple.  I assumed that the compounds listed on the active ingredient list were really the only ingredients I needed to think about.  Silly me.  Just like Round-up, and almost any other pesticide you can name, there are other ingredients that help the active ingredients work — and that could cause issues.  For Round-up, the soaps mixed in there to help the product stick can hurt frogs or other amphibians.  For Iron phosphate, the extra ingredient that could do some damage is EDTA.

So, you’re asking, what is EDTA?  EDTA is a chemical which makes metals more soluble, called a chelate.  In iron phosphate products EDTA helps the iron to be taken up into the body of the snail or slug making it work much better than it might otherwise.  EDTA is also used in fertilizers so that elements (usually iron) are taken up more readily (because they’re soluble).  But because EDTA makes metals more soluble, it also helps them get to places they shouldn’t go – like into an earthworms body.

Now don’t go thinking EDTA is bad.  It’s not.  In fact, if you ever ingest lead or some other metal you’ll be thankful for EDTA because it is used to help clear potentially toxic metals from the body.  EDTA is even present in some of our foods for various reasons.  That said, as with any chemical (including water!), it is possible for EDTA to do things we don’t want it to do in the wrong circumstances.   And that’s why we need to be more careful with its use.

As I said before, I’m still OK with iron phosphate products, especially as they compare to metaldehyde products, but you can bet I’ll be spending more time stressing its drawbacks.  I’ll also be spending more time touting beer.

For slugs of course!

Now, a question for you.  These iron phosphate products are currently listed by the OMRI (Organic Materials Review Institute) and some labels list it as being safe to use around pets and wildlife.  If the products include EDTA, should that be the case?  (You can look up EDTA in Wikipedia if you want to see how it’s made.)  Are you comfortable with using EDTA in organic production?  Does it matter to you if it’s used as a fertilizer vs. as an ingredient in a pesticide?

Well, students just finished finals here at MSU so I suppose it’s appropriate we put our faithful GP readers through their own gauntlet of quizzes…

Top marks to Terry for determining the damage on the conifer seedlings was due to incomplete overlap on the sprinklers the grower used for frost protection during our most recent freeze.  Our record-setting March warm up pushed budbreak ahead by about a month in most locations in the state.  Fruit crops (cherries, grapes, blueberries, and peaches) have been devastated but nursery crops and landscape trees came through relative unscathed until the freeze the weekend before last.

I know Linda normally handles quiz duties, but I received a couple of intriguing pictures last week.  Rather than just tell you all what’s going, I thought we’d have a little sport with it.

The photo below was taken last week ago at a container seedling nursery in western Michigan.  These are trays of container-grown spruces.  Most of the seedlings are green and growing but some are tip-damaged – with a specific pattern.  What’s going on and what caused the pattern?