Re:CULT: Leaf Spot
In a message dated 1/6/05 1:23:25 PM Eastern Standard Time,
<< I would favor other treatment including the dormant oil and fungicides or
burning or total removal of diseased plants along with better soil health
before I would the
cutting and possible spread of diseased tissue over a large area. >>
I don't spray at all. I read somewhere early on--probably in *The World of
Irises*--that if you can keep spot out of your garden for two years the problem
would be eliminated; accordingly, the drill here at Chateau Whitehall,
regardless of genus, is prompt removal of all diseased foliage and immediate discard
of all known plague ships. Overall I deem cutting less likely to dispurse
pathogens than other methods.
I believe "burning over" was invented by Ella Porter McKinney, author of
*Iris in the Little Garden* ( 1927). At any rate, John Wister credited her with
the idea. Ella's goal was the elimination of borer in her garden---*not*
disease-- so her intent was to burn the off the dried Iris foliage upon which eggs
had been laid the previous fall. Here is what she has to say on page 100 of the
"The accident of a burned over border of Irises to hasten spring
cleaning, in which no borer appeard that summer, though known to have been there
before, gave the clue which for me has solved the borer problem. I began to burn
each spring as conditions got right for burning in mid-March or a little later,
according to season, in Northern New Jersey. It was done hesitatantly at
first. The relief, though, made me bolder and squeamishness departed. I am now
only concerned that the fire does not spread, and I never attempt the burning
without a helper neearby. On isolated plantings I spray --let the faint hearted
throw up their hands in horror-- kerosene from a small compressed-air sprayer,
to make the burning hot and swift. Obnservation showed that where the fire was
hottest and quickest, there the plants were free from the pest; and too, the
kerosene assists dispatch. Waiting for the just-right day for burning delays
"When the planting is an established one, the dead blades of the iris,
lifted slightly with the fork or a rake a few hours before burning, actually
make a sufficiently hot fire to cleanse the plants of eggs. On roots planted the
previous summer, leaves or other trash must be applied.
"Clumps of I. kaempferi, I siberica, and all heavy-foliaged irises, if
in borders with other perennials, should have the dead foliage well shortened
before burning, or the conflagration is too great for neighboring plants. For
plants like I. trojana and Caterina, that keep foliage throught the winter, I
have found it best to cut this back and then apply the sharp buring. Clumps in
long borders, used in association with other perennials, I burn over
successfully by making a circle wet with the watering pot, and standing by with a pail
of water and an old broom to dab out any encroaching flame.
"The leaves persisting on the rhizomes at the time of burning will be,
of course, cooked, and will look unhappy and pallid. At that season, with a
good rain or two, new foliage soon puts out.
"Stress must be laid on the necessity of doing the buring with a Spartan
heart, fearlessly, quickly, sharply, and cleanly, even though it may, at
times, touch the bare rhizome--which does not mind a quick-racing fire, but
certainly would resent a bonfire above it.
"I do not burn over in the winter because even though physical condition
in this climate permitted it, I feel the the rhizome can better stand any
shock attendant upon the burning with vegetative growth near activity."
She goes on to say that Ii. gracilipes, tectorum, and fulva don't tolerate
buring; I. pumila does, but it makes her nervous to burn them since they bloom
so early; kerosene is not used in mixed borders; and burning "greatly lessens"
aphids and may cut down on root rot. She also says that "rusty-looking spots
on foliage may be associated with a shortage of lime.
Understand please that I AM NOT SUGGESTING ANYONE FOLLOW ELLA'S LEAD AND
TORCH THEIR SPREAD; I am simply offering some interesting expert observations from
Richmond, VA USA
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