From: Dan Levin <levin at pixar.com> on 2004.03.31 at 01:56:02(11342)
Dear Petra (and Harold),
Indeed, low humidity or even inconsistent humidity can
spoil a developing leaf in record time. A few other causal
agents one might check for (i.e. things or events which have
induced similar damage in my experience):
- Water trapped in the still folded leaf; could induce fungal/
bacterial rot. [avoid misting/ watering late in the day, treat
prophylactically with Dithane M-45 (manganese + zinc, leaves
a residue) or with Phyton-27 (copper chelate- no residue)]
- Contact with other plants, leaves or objects; I've observed
deformations if a developing leaf rubs against or even just
touches another object- spiny bromeliads especially! [keep
new leaf isolated, at least until hardened]
- Excessive air movement; can sever a primary leaf vein which
may result in a tear or perforation [keep developing leaves away
from fans] By the way, this applies even more so to the output
air stream from a forced air furnace/ heater.
- Slugs; as Obi Wan Kenobi once said, "Never underestimate
the dark side of the force...". In truth, he was referring to evil
gastropods- but popular culture misinterpreted his statement.
[you may not see a slime trail & still be plagued... check at night
with a strong flashlight & see what's lurking. I've never had good
luck using only baits in my greenhouse; best is a combination
of baiting and hand elimination inside the greenhouse- and a
dedicated regimen of baiting around the outside perimeter/ points
of entry]
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