CSI:Bonsai, final exciting episode
On our previous episode, we excluded a number of the "usual suspects"
for the Illinois mass-murder of larches, and narrowed the investigation down to two suspects isolated from the root systems of the newly deceased tamaracks. Episode 4: The first suspect was Fusarium. It causes root rot, but it is a common member of the soil community, so it is almost always possible to isolate it from a root system, whether it was causing disease or not. I was not surprised to see it. The second suspect was a fungus called Macrophomina phaseolina. It causes a disease called "charcoal rot" on more than 300 species of plants, including soybean, sunflower, and conifers. It also causes, with the help of Fusarium, a black root rot of various plants. I recognized it immediately because it forms little clumps of mycelium called "microsclerotia" that can survive for years in soil. The roots of the larch were covered with them (I'll post a picture shortly on the IBC Gallery) and when I picked these propagules out of the root and plated them on media, I got characteristic colonies of M. phaseolina. What puzzled me, however, was that this is a common and serious disease of *Southern* nurseries, but I couldn't really stretch the definition of "southern" to fit Illinois, much less the Toronto area where John Biel was reporting this problem. I also couldn't come up with a way for the larches to have become infected: the first hypothesis, that the trees had been infected when collected, was possible, but unlikely (again, Minnesota isn't "the south"), and the second hypothesis, that the trees had become infected since that time, was hard to make plausible, since Robert had never used soil in his potting mix. How would the microsclerotia have gotten to the roots? So I read up on charcoal rot. I discovered that the fungus is present in soil world-wide, but it doesn't cause disease except in hot, dry climates. Hmmm- which, this year, included MOST OF THE US! I did an internet search of disease clinic reports. Many plant disease clinics publish their reports online, which is very helpful. I help edit a journal called "New Disease Reports", and I'm always having to fact-check manuscripts called "First Report of [disease] on [host] in [geographic region]", and I have to confirm that it is, indeed, the first report of whatever whereever. Anyway, I found a couple of reports of charcoal rot on conifers in Wisconsin. Close enough. I was almost convinced on the "who" and the "why", but I couldn't figure out the "how". I sent Robert an email asking him aimless questions about whether he set his pots on the soil surface, adding "Here's an even stranger question: do you live near any soybean fields?" [we pause for commercials] One sponsor is "Turface". A rugged football player on a turface-enhanced playing field holds up a tiny potted pine and says "Great for mame, too!" Another sponsor is "Superthrive". A man in a bad toupee talks really fast while a tomato plant next to him grows visibly while we watch. Then there's a commercial for "Evergreen Gardenworks". Wow. Brent looks like a lost member of "Z Z Top"! [back to our program] A few hours later, Robert wrote back saying "Last year there was a soybean field located about 150' north of the larch. This year there is a soybean field located about 100' south of the larch." Robert owned the land and rented it to farmers. I couldn't believe it! Here was "how"! I had read that in soilbean fields, the microsclerotia persist in the debris from the last year's soybean crop, and this debris, lighter than soil, can spread in the wind. I wrote back asking Robert to ask the farmers if they had ever seen charcoal rot in the field. He wrote back this morning saying that the tenant had, indeed, seen charcoal rot. Now, this is the part of the show where you arrest the snarling perpetrator, the death of innocence is avenged, and future senseless bloodshed is averted. Only in this case, how does one stop the pathogen? There is no treatment for charcoal rot; everything I read recommended starting over in fresh or fumigated soil. As usual with plant pathologists, we think in terms of yield loss reduction, not in terms of saving cherished trees. I told Robert to put his remaining trees in a cool spot. Once autumn comes, they will be able to fight off the pathogen, but there's nothing else that can be done for them at the moment. But what about his other conifers? Are they at risk? Is there anything that can be done to protect them from blowing debris? As always, the best defense is a well-fertilized, well-watered healthy tree. You can't stop the summer sun from shining or the wind from blowing but you can make your trees strong. I'd also recommend "Rootshield" and other biological-control soil conditioners; they add mycoparasites (fungi that attack other fungi) to your soil, and although they aren't totally effective, they have been known to control diseases spread by microsclerotia. It's worth a shot. These types of fungi thrive in freshly prepared composted bark, so it would be worthwhile to repot bonsai into mixes heavy with a pine bark component. Care should be taken when repotting to injure the root system as little as possible- each fresh wound is an entryway for soilborne pathogens. And so we end this season of "CSI:Bonsai" with the cast standing in a soybean field, hoping for cooler weather..... |
Nina wrote:
And so we end this season of "CSI:Bonsai" with the cast standing in a soybean field, hoping for cooler weather..... CURSES! Foiled again! ************************************************** ****************************** ++++Sponsored, in part, by Kevin Bailey++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
Well Nina, looks like you've exactly described what's happening to my larch.
I'm a newbie (3 years) and I'm still learning how much to water my trees, and until now, I wrote this off to over watering However, three months ago one of my Larch (apparently very healthy) turned brown and died in a matter of days! A month later, two smaller ones did exactly the same thing. Within days they went from bright green to brown sticks. Just so happens, last year I was surrounded by soybean crops. LARGE fields of them. Usually, these fields are filled with corn, but for some reason, last year the farmer switched to soybeans. This year he's back to corn again. Is it possible a pathogen was blown from the soy fields last year and sat dormant in my larch plantings until the extreme heat of this summer triggered something ? If one of my larches in a forest planting gets infected, must I assume they're all going to die? Heaven forbid ! Mark Hill - Harrisburg, PA - Zone 6 -----Original Message----- From: Internet Bonsai Club ] On Behalf Of Nina Sent: Thursday, August 18, 2005 9:39 AM To: Subject: [IBC] CSI:Bonsai, final exciting episode On our previous episode, we excluded a number of the "usual suspects" for the Illinois mass-murder of larches, and narrowed the investigation down to two suspects isolated from the root systems of the newly deceased tamaracks. ************************************************** ****************************** ++++Sponsored, in part, by Kevin Bailey++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
well, I have to admit that my own story seems a little too "neat",
almost like it really *was* written for television. On the other hand, probably no one has done a study on "risk factors affecting conifer bonsai grown in proximity to soybean fields". I'm not going to speculate unless you send me the next dead conifer you have. Or heck- you're so close, I'll make a house call! But we need more data before we can make any broad demands banning soybean production in the US. I'm going to assume that the key factor here is the heat: in fact, one of the Wisconsin disease reports I found diagnosed the sick Thuja as follows: "Stress/Fusarium/charcoal rot", making the assumption, as I would have, that the stress was a crucial ingredient. Let's remember where larches grow in natu in bogs. A native larch will never, ever dry out, even for a day. A bonsai larch is subjected to new and different stresses. If I had a forest planting and one tree died, I'd certainly try to figure out what killed that tree. If it was a soilborne disease, I'd repot in fresh soil as quickly and carefully as possible. But it wouldn't be surprising if the other trees had "latent" infections that didn't become apparent until the next stress. Nina, waiting to be sued by the Soybean Growers Anti-Defamation League. |
Mark: Crop rotation is just good agricultural practice. When I
was a kid in Illinois, corn farmers always planted soybeans about every third year. Soybeans nitrogen fixing properties help restore the soil, so that the fields don't just wear out and produce weaker crops over the years. Alan Walker http://bonsai-bci.com http://LCBSBonsai.org -----Original Message----- From: Mark Hill Just so happens, last year I was surrounded by soybean crops. LARGE fields of them. Usually, these fields are filled with corn, but for some reason, last year the farmer switched to soybeans. This year he's back to corn again. ************************************************** ****************************** ++++Sponsored, in part, by Kevin Bailey++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
On Aug 18, 2005, at 11:24 AM, Nina wrote:
snip I'm going to assume that the key factor here is the heat: in fact, one of the Wisconsin disease reports I found diagnosed the sick Thuja as follows: "Stress/Fusarium/charcoal rot", making the assumption, as I would have, that the stress was a crucial ingredient. Let's remember where larches grow in natu in bogs. A native larch will never, ever dry out, even for a day. A bonsai larch is subjected to new and different stresses. I lost one larch that I repotted this spring. I suspect it was the heat. My smaller larch is struggling but holding its own. Craig Cowing NY Zone 5b/6a Sunset 37 ************************************************** ****************************** ++++Sponsored, in part, by Kevin Bailey++++ ************************************************** ****************************** -- The IBC HOME PAGE & FAQ: http://www.internetbonsaiclub.org/ -- +++++ Questions? Help? e-mail +++++ |
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