#2: Re: black spot
Posted on 2006-06-18 20:31:58 by Warren
Doug wrote:
>I have a climbing rose bush and out back there is a red tip. Both have
> black spot. The poor rose bush didn't have it the first two years in
> the
> ground and it climbed and was healthy as anything could be. Now it
> can't
> sustain the roses and is failing miserably. How can black spot be
> destroyed
> permanently?
It can't be. Black spot is a fungus. The spores cannot be effectively
destroyed, and even if you use a backhoe, you're bound to leave some
behind.
Reducing black spot takes planning. If you must choose varieties that
are susceptible to black spot problems, make sure that where you place
them gets plenty of sun, especially in spring, and make sure that you
prune to encourage an air flow that will dry the rain and dew quickly.
While you can't stop Mother Nature from raining on the plants, you can
refrain from wetting the foliage when you water. Use drip irrigation or
soaker hoses (not the ones that spray, but the ones that weep) when you
water, and allow the surface to dry before watering again. Clean-up any
leaves, prunings, dropped foliage, etc. Don't use prunings from roses or
other plants with black spot in your compost -- or at least not if you
plan to use that compost anywhere near plants susceptible to black spot.
If you know that a plant is susceptible to black spot, starting in early
spring you can use a systemic treatment such as Bayer's 3 in 1 for Rose
Care. (This is the liquid stuff you mix in a watering can, not the 2 in
1 granular stuff.) Retreat every 4 to 6 weeks until the dry season.
Once black spot appears, prune away any foliage that has black spot. Be
careful while pruning, as the more you disturb the foliage, the more the
spores will be set free, and settle in the soil. If you're removing a
substantial amount of foliage, you may also want to remove any mulch
around the plants, too. Like I said at the top, you won't be able to
totally remove all the spores, but the fewer you leave behind, the
easier time you'll have controlling them next year.
Once you remove all the black spot affected foliage, you can try using
the Bayer 3 in 1 systemic, but continue to prune away any new black spot
affected foliage at least twice a week -- daily if you can -- until
things get better. And remember that part of why things will get better
will be the generally drier weather of summer, and the hotter sun. Once
conditions better suited for fungus growth comes back, so will your
problem.
It may take you a year or two to get things under control. But if you've
got the wrong plants in the wrong place, you may never see an
improvement. Varieties susceptible to black spot located in a shady spot
that has no air circulation will likely never get much better, and
you'll be fighting a losing battle.
--
Warren H.
==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.
Power Lawncare Tools for Spring Clean-up:
http://www.holzemville.com/mall/blackanddecker/
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