Month: March 2011

Bordeaux Mix

One of my favorite stories about pesticides is the story of Bordeaux mix.  It’s a story of France in the 1800s (so it must be pretty romantic, right?) and how they were suffering from a shortage of grapes.  Don’t feel sorry for them — it was really their own doing.  Over the course of the 19th century grape vines were brought from the United States to test their merits against European grapes.  It was quickly discovered that, for the most part, American grapes were not the equal of European grapes for winemaking.  Unfortunately for the French, however, along with the grapes came a disease: downy mildew.  This mildew absolutely ravaged grape vines across Europe, and particularly France from the time that it was introduced, around 1878.

Meanwhile there was another problem for grapes growing in France.  People.  People like to eat grapes beside the side of the road and so, throughout France’s grape growing regions, grapes on the sides of the road were typically bare.  Unlike downy mildew, however, grape growers had a pretty good idea what to do about people.  They sprayed nasty stuff on the grapes.  This nasty stuff took many forms, but the one which was most effective was a mixture of copper sulfate (basically you dissolve copper in sulfuric acid) mixed with lime.  Brushed on a plant’s foliage, it was darn ugly.

Then came 1882; a terrible year for downy mildew.  Grape vines were losing their leaves all over Europe, except for those vines beside the sides of the road.  There the grape vines were doing just fine.  The reason was the copper in the lime/copper sulfate mixture which was eventually dubbed Bordeaux mixture because of where it was first used.  Bordeaux mixture is still available today, and is one of the most important tools in the organic grower’s pesticide arsenal.  Unfortunately it’s nasty stuff – it builds up in the soil and it’s toxic to earthworms and a wide variety of different plants and aquatic organisms.  Using this stuff once in a while – such as once a year – isn’t terrible, but regular use is a good way to ruin your plot of land.

One final thought – Those American vines which originally brought in mildew?  They eventually became very important to French wines because of another introduced pest, phylloxera.  They were used as rootstocks because they were resistant to this pest — unlike European grapes.

A salt bath for your tomatoes?

This morning I got an email from one of my gardening colleagues, wondering about the wisdom of watering tomato plants with salt water.  He had a link to a UC Davis website which tacitly endorses spraying tomato plants with 10% salt water “to increase their nutritional value and taste.” Unreferenced “worldwide studies” are mentioned, along with the “major potential benefit of providing irrigation for crops in areas with freshwater restrictions.”

Before we deal with the impracticalities and out-and-out harm of using salt water for irrigation, let’s look at why this practice would work on tomatoes.  By training I’m a plant stress physiologist (and I’m well versed in the primary literature on this topic).  Watering tomato plants with a salt solution imposes a drought stress on the entire plant, as less water is taken up under these conditions.  So leaves and fruits are smaller and they may produce stress-induced biochemical compounds in response.  The upshot is that you have smaller tomatoes with a higher concentration of various solutes, some of which might be tastier or more beneficial to humans.

Guess what?  You can do the same thing by decreasing irrigation during fruit set!  Less water means smaller fruit and increased concentrations of sugars and other plant compounds, and voila!  So you can skip that step of adding salt water and just cut back on irrigation to induce a mild drought stress.

So…why in the world would you dump salt water on your garden soil?  The article blithely dismisses this:  “Many are still concerned about salt causing soil degradation and rendering some seawater-treated tomatoes inedible, but scientists cite that plants thrive in balanced soil containing both macro- and micronutrients.”  Sorry, but sodium is NOT a micronutrient for most plants and does NOT contribute to a “balanced soil” in one’s vegetable garden.

An ironic twist to this whole article is that most of the research that’s been done is relevant to arid parts of the world (the Middle East, primarily) where saline soil conditions and limited water are common.  I can’t imagine what they would think about people who would deliberately contaminate good soil by adding salt water to it.

Jeff Gillman a.k.a. Dr. Unbiased!

“Everyone’s taking stands, and unfortunately, some of those taking the strongest stands have the least information.”
– Dr. Jeff Gillman, on “How the government got in your backyard”, co-authored with Eric Heberlig

Fine Gardening did a fine job in a recent interview that was linked to their e-mail update.  FG Editor Steve Aitken brings some humor as he quizzes Dr. Jeff. about his new book.  Check it out here.

Steve opens with “Is the government really in my backyard? And if so, can I get them to pull some weeds?”

Hee!!!  The interview awesomeness continues as herbicides, nudity, tofu dogs, and  poo-pooing are all discussed. I just may renew my subscription, if Steve can promise more of the same. I gave up on Garden Design years ago – since I don’t have a gravel garden with infinity pool overlooking a canyon in California, nor am I interested in $5000 lawn chairs. Reading it just made me feel dowdy.

“I can practically guarantee that you’ll find something in this book that
you don’t like.”  Way to sell a book, Dr. Jeff!

Despite waiting pensively by the mailbox for my Complimentary Copy which has yet to arrive, I can safely say there’s already a kerfuffle brewing over the book. As Jeff noted in his post last week, folks have already weighed in DISAGREEING with his position. Wait! He has no position! That’s the whole bloody point. It seems an alarming number of people aren’t sure what to do with the 1,350 grams of gray stuff between their ears.

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Relative to last weeks “trivia” post: I’m apparently the tallest Garden Professor, at 72 + 5/8 inches.

What can CO2 do for you?!

Well, it looks like the climate change skeptics are starting to hedge their bets.  Global climate is not changing.  But if it does change, it’ll change for the better.  At least that’s the gist of a book by the Center for the Study of Carbon Dioxide and Global Change entitled “The Many Benefits of Atmospheric CO2 Enrichment”.  The book documents 55 different ways that increasing global CO2 will benefit the world.  Most of this is built on studies documenting increases in plant growth and/or photosynthesis associated with increasing CO2.  If you’re interested you can look at a preview of the book at:

http://www.co2science.org/education/book/2011/55BenefitsofCO2Pamphlet.pdf

While CO2 enrichment can benefit plants and trees in the short term, it’s less clear how they will respond over the long term.  For example, nutrition or water may soon become limiting such that the full CO2 ‘fertilization’ effect is never realized.  Also, it’s likely that certain plants will benefit more from increased CO2 than others: Will exotic invasives gain an additional advantage over natives?  And, of course, if rising CO2 results in increased global temps (which the Center denies) then all bets are off.

 

You can learn more about the Center for the Study of Carbon Dioxide and Global Change at their website http://www.co2science.org/  There is a tab on the homepage where you can donate to support their cause.  Why not?  Exxon/Mobil already has.

Wet trunk – the whole story

We had a flurry of discussion on this over the weekend. The diversity of possible answers shows you how difficult it is to do diagnosis with only some of the information available. That being said, several of you (Gail, Tom, Dave and Jimbo) all had portions of the problem identified. Here’s the whole picture:

As both trunks of this double-leadered tree have continued to expand in girth, they’ve created the perfect conditions for disease to occur in the narrow constriction between the trunks. Though I’m not a pathologist, I would agree with an initial diagnosis of slime flux.

In addition to the poor structure and disease issues, the location of this tree – next to a street, sidewalk, houses, and across the street from a school – simply shouts for removal before it inevitably fails and causes damage or injury.

Nice job – and thanks for doing your homework over the weekend!

Friday puzzle: wet trunk

Another diagnostic question today.  Below you can see the lower portion of a tree trunk whose left half is obviously wet:

What is directly causing the wetness (in other words, what environmental factor), and can you guess what led to this problem indirectly?

I’ll eliminate some of the obvious possibilities:  it’s not from dog pee, nor is it from a directional sprinkler.  And the answer to the second question is not in this close up photo, but will be revealed on Monday.

Why do I torment you like this?  Well, if nothing else, it gives you an idea of what distance diagnosis can be like – which is what we tend to do more and more, thanks to the internet and digital cameras.  Someone will send a photo of a plant problem and expect us to figure it out, but the answer may lie outside the field of view.

In any case, have fun!

Building a House of Straw — With Brix!

Before I get into the meat of this issue I wanted to mention that, a couple of weeks ago, Purdue came out with a statement which basically supported a post that I had previously written – one where I stated that there’s not a lot of good evidence that using Roundup leads to sudden death syndrome in soybeans. Yeah me! Well, not really – that’s not the way science works. While it is nice that other scientists agree with my conclusion, that doesn’t mean that Round-up isn’t affecting soybeans – it just means that there’s no evidence of it right now. Science doesn’t stop because a few scientists agree.

Same with compost tea – Linda and I have both posted about compost tea and we agree that, at this point, there’s no reason to use it. But science doesn’t stop, and it wouldn’t be completely surprising if, someday, someone comes up with a compost tea type product which is actually reliably useful.

Now on to the flavor of the day! Brix. So, what is brix you ask? Brix is a measurement of solids in a water (usually these solids are sugars). It’s easy to test brix by using something called a refractometer which measure how light bends when it passes through a thin film of water. We use brix in foods to tell how sweet they are. We just take a little sample of sap or juice, put it on a refractometer and bang, we know about how much sugar we have (actually, as I mentioned earlier, any dissolved solid, not just sugar, can alter measurements, as can non-solids, like alcohol. But the dominant thing affecting the brix measurement is usually sugar content).

Though it isn’t exactly mainstream, there is something out there called brix based gardening. Basically, the goal of brix based gardening is to increase the brix of the food we eat. Increasing the brix means increasing the sugar. The theory is that the higher the brix of a food the better it is – in terms of taste, resistance to insects, resistance to disease, healthiness.  The list goes on and on.

The biggest problem with arguing that gardening based on brix is a bad idea is that there is a nugget of truth in brix based gardening. Moreso than compost tea (in my opinion), brix has proven itself useful in certain situations.  Particularly in wine making, brix is used to quantify the sugar content of your grapes so that you can predict the sweetness of the wine you will produce (it will also help tell what level of alcohol you’ll get). As time goes on at the end of the season grapes increase their sugar content, so grapes are picked according to when the brix is right for the wine you want to produce.  Another grain of truth is that with higher brix you’ll get less insect pressure. This stands to reason, at least to some extent, because insects are usually looking for nitrogen rather than sugar.

But along with the little grain of truth comes some BS. For example, the idea that eating a food with a higher brix reading means that you’re eating a healthier food is just silly. It just means that you’re eating a sweeter food. The idea that higher sugar levels mean a healthier plant is also silly. In fact, one of the most significant things which can make brix go up is putting the plant under drought stress. Under drought stress, with less water, the concentration of sugars in sap naturally increases (because there’s less water to dilute it). Raisins are sweeter than grapes! Furthermore, the variety of the plant which you grow has an extreme effect on brix. Chardonnay grapes may have a low brix (around 21), a late harvest Riesling may have a brix of 42!

I have seen an inordinate amount of gobbledygook about mixing different fertilizers to get the perfect ratio of nutrients to increase brix. First, it’s important to realize that fertilizers can alter sugar content. For example, fertilizing heavily with nitrogen will increase growth of the plant but will usually decrease sugar concentration (hence brix). Indeed, from what I’ve seen, nitrogen seems to be the biggest player in sugar content.

That said, calcium and phosphorus based fertilizers seem to be the favorites among brix based gardeners – but from what I can find research hasn’t actually shown that these fertilizers increase brix on anything approaching a reliable basis. Another common recommendation is a molasses based fertilizer – once again, research on molasses doesn’t seem to show that it can do much to increase brix. Honestly, it looks to me like those recommending high brix as necessarily a good thing for us and our plants and then offering methods to do it are putting a scientific veneer on witchcraft – at least until further research comes along. I am sure that those favoring brix-based gardening will disagree with me – if you do and you read this I would welcome seeing some published papers which support your claims.

Parking tickets, compost tea, and pseudoscience in the Ivory Tower

Back in November 2009, Jeff posted an educational and amusing commentary about Harvard’s use of compost tea. Much vigorous discussion followed, and we’ll return to that topic in a moment. But first, I’d like to tell you about my morning yesterday.

In September of 2010, I received a ticket for parking longer than 2 hours in a restricted zone. Now, there was no way I committed this infraction; I had hard core proof that could not be rationally challenged. So, armed with my husband’s affidavit as to my whereabouts, as well as a dated receipt showing I was at the post office at the time when I was apparently parked several miles away, I went to court to challenge the ticket. During our briefing, the sitting magistrate told us we would need to provide a “preponderance of the evidence” to win our respective cases. For me, it was an anticlimactic turn of events, as the citing officer (whom I’d subpoenaed) did not show up, so the ticket was dismissed for lack of evidence.

And thus we return to today’s subject – use of compost tea without a “preponderance of the evidence.” Jeff took Harvard to task for buying into this “bullpucky”, I think he called it, and now Berkeley has decided to drink the Kool-Aid. One of my dear colleagues at University of Washington forwarded me a link announcing that Berkeley Botanic Gardens was adopting compost tea as an “eco-friendly fertilizing method.”

As the article reports, compost tea is being used

1) as a disease suppressant
2) to provide nutrients, and
3) to reduce the amount of water needed.

I’ve written a lot about compost tea, and I’ve reviewed journal papers on the topic as well. In a scientific nutshell, there is no solid evidence to support use of compost tea, particularly aerated compost tea, in disease suppression. Likewise, there is no evidence to support a nutritional role (I just finished reviewing a manuscript on this topic and the data were unconvincing). Finally, I cannot understand why spraying compost tea onto the leaves of a plant would reduce its water requirements. The “preponderance of evidence” is truly lacking.

Students at Berkeley have the dubious honor of supporting this nonsense through their student fees: $11,000 has been spent on a 300 gallon tank, worm composting bins, and a spray tank.

Whatever happened to using good old compost, and letting nature create its own “tea?” (Compost used as a mulch also helps reduce irrigation needs.)

Lasso those grasses!

While Jeff and Bert were swilling beers and eating burgers last weekend (dang, wish I was there to commiserate!) I was whacking back the last of the perennials and grasses in our home garden.  Tarp after tarp were filled with winter’s debris for compost pile as we fought 25 mph gusts the entire time.  Not ideal conditions.  However, a neat trick I learned years ago came in handy with the grasses.  I’m assuming many of you utilize this technique also – so forgive me if this is a “nothing new” post  Here’s Paul and Dabney, our Hahn Horticulture Garden horticulturists, demonstrating said technique:

Just cut below the web strap or rope with your favorite implement of destruction, and toss the whole bundle on the tarp to get it to the pile. Note that they both have on safety glasses, and Dabney has on gloves.  I can’t stress enough the importance of gloves (and long-sleeved shirts) when handling dried grasses. One of our student workers sliced his finger open to the tune of three stitches last week.  He was cutting down Arundo donax, Paul asked him to put some gloves on, but since 22 year-old guys are indestructible, he blew off the advice. Just saw him working out in the garden today with gloves on, yay!

Weigh in with YOUR garden clean-up tips – ’tis the season (for most of us north of USDA Zone 7 in the northern hemisphere).

Garden Professor Trivia #2: Who’s the tallest GP?

[This could get interesting…Oldest! Weirdest! Heaviest drinker! Most traffic tickets! Most cats! Most obsessed with slugs! etc.]