On the previous episode of CSI:Bonsai, Robert had a group of larch that
were dying one by one. He suspected a mysterious wilt that had been
reported by other larch growers, but whose cause had never been
determined. Robert decided to send a couple of dead trees to Dr.
Shishkoff, forensic botanist.

Today's episode: Robert packed the trees better than 90% of people
sending specimens to plant diagnostic clinics: he cut each tree into
several pieces for easy packing, then placed the pieces in a ziplock
bag along with a moist paper towel, then shipped the specimens by
priority mail. They arrived today in good shape.

I immediately unpacked them and examined the symptoms. One tree was
extremely dead: the inner bark was a uniform brown from root to shoot
tip. The other tree, however, showed a gradation from extremely brown
bark on the roots and crown, going to healthy bark at the tip. This is
extremely important, and explains why I insisted on getting very recent
corpses. First, the disease obviously started at the bottom and moved
up: this tells us we're dealing with a root or crown pathogen, not a
stem blight pathogen. Second, the most likely place to isolate the
pathogen is at the margin between diseased tissue and healthy tissue.
In a plant that's been dead for a while, saprophytes and secondary
pathogens swoop in like vultures and make it hard to find the causal
agent.

I took samples and plated some on regular media (V-8 agar, made from
V-8 juice and a solidifying agent)and a selective medium specific for
water molds (PARP, with sterols and fungicides added). I also put
pieces of plant tissue on moist filter paper in a moist chamber, to
encourage the pathogen to fruit (easier to identify that way). I'll
check on these next week and see what shows up.

Nina

Nina wrote:
I took samples and plated some on regular media (V-8 agar, made from
V-8 juice and a solidifying agent)and a selective medium specific for
water molds (PARP, with sterols and fungicides added). I also put
pieces of plant tissue on moist filter paper in a moist chamber, to
encourage the pathogen to fruit (easier to identify that way). I'll
check on these next week and see what shows up.

Nina

The Kay Scarpetta of the bonsai world. :-)

Jim Lewis - - Tallahassee, FL - Nature
encourages no looseness, pardons no errors. Ralph Waldo Emerson

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