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August 27, 2010

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EPA requires applicators of Captan to wear a respirator, rubber boots, goggles, rubber gloves, long sleeves etc. Captan is labeled "Danger" which is the highest toxicity level for applicators. It has a 72 hour post spray worker reentry period.

EPA labels Phosphite "Caution" which is the lowest toxicity level. It has a 4 hour post sparay worker reentry period.

EPA labels copper "Caution" also the lowest toxicity level for applicators. There is a 24 hour post spray worker reentry period.

Copper levels in our soils at Shinn are less than 10% of the mg/kg levels sighted in your post as toxic. This has been documented by yearly soil testing.


My comparion between Captan and phosphite may not be the most apt. However, it's important for consumer to be aware that organic does not necessarily mean harmless.

There are plenty of other effective fungicides with "caution" warnings and short REIs that are not organic.

Tom, I can't help but feeling a little disappointed by this post. The only part that addresses biodynamics is one question that basically says it can't be tested. I know looking at organics in general makes sense in the context of this series, but the series is supposed to be about "The Science of Biodynamics", isn't it?

Why bother with the series if the answer is going to be "we can't really say anything scientific about it"?

Yet that is not the case, since a scientific article quoted in a tiny footnote, about long term differences between "regular" organic and biodynamic says that, and I quote: "Biodynamically treated winegrapes had significantly higher (p http://www.ajevonline.org/cgi/content/abstract/56/4/367.

That does seem to mean that something is different about biodynamic grape growing, doesn't it? And to me, that is a much more significant thing to look at than just saying we won't study biodynamics because there is no legal production standard for horsetail tea.

Also, it's true that the synthetic vs non-synthetic question is interesting in terms of how meaningful organic certification is, but that addresses the (in)adquacy of certification more than the actual science of biodynamics. And David's point on Captan tends to score one for organics: whether synthetic or not, I'd rather go for the more innocuous products.

There are many, many ways of getting sidetracked, in this whole debate. I certainly encourage you to remain focused on central issues on your announced topic.

Finally, one thing struck me in Alice Wise's answers. She said that: "We ended up using a conventional nitrogen fertilizer this year just because vine size was declining so much." Didn't that just invalidate the whole organic trial? And couldn't the vine size issue mean that the methods used in the trial were inadequate or insufficient (there are many ways to go about managing vines organically), rather than "organic doesn't work"? A little preparation 500, perhaps?

As for the article that Remy quoted, we must first note that is but a brief abstract of the entire study so we must be careful drawing conclusions from it.

Check out this article which discusses that study (http://www.finewinemag.com/docs/BIODYN~1.PDF) which quotes the study as stating: "there is little evidence the biodynamic preparations contribute to
grape quality. The differences observed were small and of doubtful practical significance.”(Reeve et al, 2005, pp.371–74)

That article has plenty to say about other studies as that try to assess biodynamics.

Remy: It's true that this is a bit of a sidetrack. However, I wanted to highlight the challenges presented to growers in LI who would eschew conventional herbicides/pesticides. The environment makes it very difficult, particularly with downy. I don't think an interview with an industry professional is completely off track.

Your comment got cut off, but I assume you were referring to the higher anthocyanin/polyphenol content found in one year of the study. Allow me to quote the conclusions of the CA study:

No differences in soil quality at 0 to 15 cm were found between biodynamically treated and untreated plots. Also, no differences were found in microbial efficiency as measured by biological quotients. That is consistent with other studies in that effects of biodynamic preparations have been recorded in some situations but not in others. The effects of a single application of compost and an annual rye green manure crop on soil parameters in this study could be detected for several years, suggesting that only minimal compost application and limited use of green manure crops on fertile soils is needed to achieve lasting benefits in a lower-yield, high-quality winegrape system such as in this study.

Leaf tissue analyses showed no differences between treatments. In addition, most plant nutrients were within recommended ranges and deficiency symptoms were not seen in the vines at any time. Yield, cluster count and weight, and berry weight showed no difference between treatments, and disease pressure was minor in all blocks. Although average pruning weights for both treatments in 2001 to 2003 fell within the optimal range of 0.3 to 0.6 kg/ m for producing high-quality winegrapes, ratios of yield to pruning weight were significantly different and suggested that the biodynamic treatment had ideal vine balance for producing high-quality winegrapes but that the organic vines were slightly overcropped.

Biodynamic grapes in 2003 had significantly higher Brix and notably higher total phenols and total anthocyanins. These differences, however, were small and of doubtful practical significance.

The biodynamic preparations were the only factor different between the management treatments in this study and may have caused the observed differences in ratios of yield to pruning weight as well as the small differences in winegrape chemistry. If so, the mechanism (or mechanisms) responsible for the few differences seen in this study is not known.

Again, I will address this in more detail in the next post, which will be about preparations 500-508 and their effects.

"Biodynamic grapes in 2003 had significantly higher Brix and notably higher total phenols and total anthocyanins. These differences, however, were small and of doubtful practical significance."

This seems to be the key paragraph in this post. Ask any winemaker whether "significantly higher Brix and notably higher phenols and total anthocyanins" will make any practical difference in the quality of thier wine.

And Barbara adds this to the discussion as one reason why she will never give up the way she chooses to farm:

Today I remember a walk through the vineyard that took place last year. An extension agent from California came to see the vineyard hosted by another extension agent from the east coast. When the California visitor realized we farm biodynamically he cited a study that found there was a difference in sugar levels in grapes grown with biodynamic methods versus grapes grown organically. The biodynamically grown grapes were a half Brix higher in sugar than the ones grown organically. The east coast extension agent shrugged their shoulders and was unimpressed and stated “Only half a Brix?” implying that was not so much of a difference. The west coast extension agent took exception and replied “That is a lot. It is remarkable”

Two academicians. Measurable scientific evidence. One shrugs it off, the other finds it remarkable.
Even when Biodynamics is measured through empirical methods our scholars still can’t agree.

So according to one study, biodynamically grown grapes result in a higher level of potential alcohol? Great, just what we all need.

Tom, thanks for quoting the article more extensively, after my comment somehow appeared incomplete.

I'm with David on this. I don't see how you can say, at the same time, that there was "significantly" higher brix and "notably" higher total phenols and anthocyanins, and then turn around and say these differences are "small and of doubtful practical significance."

They're either significant or they are not. I believe they are significant. Otherwise, can someone explain to me why "phenolic ripeness" has been such a buzzword in the wine world, these past few years?

Richard, my point wasn't to say that biodynamic winegrowing is systematically better. My essential point was that Alice Wise seems to say "we just can't measure this stuff", and that's the end of that, but at the same time quoting an AJEV study that says there are "notable" and "significant" effects in the grapes. So apparently, there is something measurable, isn't there?

I look forward to the next installment, as it takes a closer, more systematic look at preparations, something more central to the topic at hand.

In the meantime, this paper by one of the researchers involved in the 2005 study, Jennifer Reeve, gives interesting perspectives on the results of the study and how we should look at them:
http://www.redwhiteandgreen.com.au/docs/TakingAScientificLookAtBiodynamics.pdf

Looking forward to the next pieces.

Remy:

I think part of the confusion here might be semantic. "Significant" here refers to "statistically significant". The p-values referred to are <.05 and <.1 for "significant" and "notable" in these cases, meaning that there is a 95% and 90% probability that these differences are not due to random chance.

The actual numbers for Brix in 2003 are 25.88 ± 0.09 for BD and 25.55 ± 0.17 for control, an average difference of about 1%. It's statistically significant, meaning it is not likely due to the experimental error in measuring, etc., but it is a small difference in magnitude that was observed in one of the four years of the study.

Thanks for clarifying that, Tom. I'll read through the whole paper, and will have a more precise idea.

Remy:
I certainly agree with you that further scientific study would be beneficial. There have been few studies done so far, and the majority seem to indicate no differences from biodynamic preparations. And this lone 2005 study seems to offer contradictory conclusions, and at best, indicate a reason why additional research is needed.

But, new studies really need to be conducted as best as possible, starting with a good set of starting parameters and definitions.

I think the issue of labeling of fungicides is interesting.

I double-checked a Captan label this morning and the Captan 4L formulation from Drexel requires essentially the same Personal Protective Equipment (PPE) as Phostrol (a phosphite material). Neither one requires a respirator as reported in a previous post (although that doesn't mean there isn't a label for a different formulation that does). However they both require the mixer/handler to use the following PPE:

1)long-sleeved shirt and long pants
2)protective eyewear
3)chemical resistant gloves
4)shoes and socks

This is pretty typical for most fungicide materials.

And the REI for Captan 4L is 48 hours not 72 hours.

The copper labels I looked at this morning included:

1)copper hydroxide which has a EPA classification of DANGER, the highest level

2)basic copper sulfate with an EPA classification of WARNING (rather than caution)

Although, there may be labeled formulations of copper products on the market with the CAUTION class.

Phosphites do indeed have a CAUTION classification, as do other Downy Mildew fungicides such as Abound, Mancozeb, and Revus.

Other considerations include the Acute Toxicity or oral LD50 of the material (single dose in mg chemical/kg bodyweight that killed half the rodents during the toxicological testing of the material---the lower the number the more acutely toxic)

Captan 10,000
Phosphites >5,000
Mancozeb >5,000
Revus >5,000
Copper hydroxide 1,000
Copper sulphate 472

Anything with an LD50 over 5,000 mg chemical/kg bodyweight is considered non-toxic (acute toxicity). 50 mg/kg or less is considered a poison. At 472 mg/kg, copper sulfate is only considered "moderately toxic".

Or you could look at soil persistence or Soil Half-life(the higher the more persistent):

Copper hydroxide 2,600 days
Copper sulfate 2,200 days
Mancozeb 70 days
Revus 50 days
Phosphites 20 days
Captan 3 days

At 50 days Soil Half-life, according to theory, the entire amount of the material entering the topsoil would be degraded within one year.

One note of caution when considering these numbers, most of them are taken from USDA databases and represent the "harmonic mean" of many studies, not a single study.


I think a lot of different aspects of a chemical's attributes and behavior in the environment should be taken into consideration.

I am happy to have the phosphite materials available for me to use in my Downy Mildew prevention program because they are of low toxicity, although they are limited because they ONLY prevent Downy Mildew. We just have to insure that we don't overuse them and bring on pathogen resistence.

Unfortunately, Phopshites are not available for use in the National Organic Program's organic certification program. Or for the same reason in any BD certification system.

Larry:

I considered adding a table of half-lives/REIs of various fungicides, but abandoned it at the last minute. Thanks for saving me the effort!

My pest management guidelines from Wayne Wilcox at Cornell Cooperative Extension back up my previous post.

This from the EPA:

Captan was previously cited as a probable carcinogen by the EPA but is now classified as "not likely" to be a human carcinogen at exposure levels associated with agricultural use.

I forgot to add this information about Captan to my last post.http://pmep.cce.cornell.edu/profiles/extoxnet/24d-captan/captan-ext.html

In a study to determine copper toxicity to earthworms they grew worms in soil with 242 ppm copper for 112 days to dose them. 242 ppm represents around 500 pounds actual in the acre-plow-layer. Doing the math - if you apply copper to vineyard soils at the Demeter standard of 3 pounds actual per acre per year it would take over 166 years before the soils would become toxic to earthworms.

David: Thanks for the info. Do you have a reference for that earthworm study?

The Discussion section of study that I cited (Eijsackers et al., abstract at http://linkinghub.elsevier.com/retrieve/pii/S014765130500031X) reviews many, many studies on earthworm reactions to copper and gives numbers as low as 33 ppm as critical concentrations of bioavailable copper (23 years using the same math).

In the same study, they found that burrowing behavior of the earthworms in vineyard soil was lower than that in adjacent grassland and comparable to copper-spiked soil. That is, copper, even at the levels found in the vineyards tested (14.4 ppm) negatively affected earthworm behavior.

If anyone would like to actually *read* the study, I'd be happy to email the full PDF if contacted privately.

I don't think that information is accurate. The most modern work being done right now on the impact of soil copper on earthworms is happening out of Lukas Van Zwieten's lab in Australia.

The article below is a very good summary.

Concentrations of 20,30,40 ppms (mg/kg) of soil copper have a serious impact on earthworms. It drives them out of the topsoil.

Van Zwieten is the foremost researcher in the field right now.

http://www.tuckombillandcare.org.au/projects/Fungicides%20and%20Soil%20Health.pdf

The avocado orchards cited in the Van Zwieten study are applying over 20 times the amount of copper per acre as is allowed by the Biodynamic standard. This probably accounts for the problems they are having with earthworms.

I believe if you read the study carefully you will see that the highly Cu-polluted orchard soil was chosen as a source of soil. The same soil was sourced nearby where copper had never been used. The researchers then blended the two soils into a series of new soils with descending Cu concentration. From 100% contaminated soil (over 700 mg/kg)in descending succession to 100% uncontaminated soil. The blends produced the series: 0, 5, 10, 25, 50, 100% Cu-contaminated soils.

The study then went on to show that earthworms avoided soils with as little as 44 mg/kg Cu.

The graphs on pages 4 and 5 of the paper I linked show quite clearly earthworm avoidance of relatively low levels of soil copper, even below 44 ppm.

As far as estimating how much copper is actually in a farm soil, it is critical to understand that copper is very quickly and tightly bound to soil organic matter and fine mineral particles (clay and silt) in the top couple of cms of soil. Using an "acre-furrow-slice", which is the upper 7 inches (17.5 cm) of soil is not used in studies because the Cu is concentrated in the top couple of cms, and using 7 inches to sample will dilute the estimate of actual Cu concentration that is effecting earthworms and the soil biota in the top few cms of soil.

So we would have to divide 166 years by 7 to estimate what will happen in the top 2.5 cms of soil. That equals only 23.7 years.

It is not simple to determine exactly how much copper would enter the soil with each application. However when the National Organic Standards Board studied copper sulfate for inclusion in the NOP as an algicide in 2001, their Technical Advisory Panel (TAP) issued a report that did study these matters of soil pollution.

http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5067070

One of the three scientists reviewing the potential inclusion of copper sulfate did cite a study that estimates it. On page 5 of the TAP report, he quotes from a paper (Besnard 2001)that "Each addition of 10 lbs/acre of copper sulfate (2.5 lbs actual copper) could increase the concentration (of copper)in the top two inches of soil by 6 mg/kg or 6 ppm."

My personal calculation estimates that 11.7 mg/kg actual Cu would enter the top 2 inches based on a single application of 3 kg/ha actual copper. Reducing it to 2.5 kg/ha actual Cu to compare to the previous estimate, it results in 9.7 mg/kg Cu in top 2 inches of soil.

My estimate is based on the assumption that 100% of copper applied as a fungicide would enter the soil, which is not completely likely, so we might choose to use the lower estimate of 6 mg/kg Cu in the top 2 inches from the NOSB TAP report.

It will not take many years of use at the 3 kg/ha application rate to result in 40-50+ mg/kg Cu in the top 2 inches of soil. 40 mg/kg (ppm) in the top 2 inches of soil could be achieved strictly by addition at rate of 6mg/kg/year in 6.66 years. Perhaps it will take 10 years.

These are only estimates, but they are based on work done for the National Organic Program, by their Technical Advisory Panel.


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