blackspot, was RE: [compost_tea] Re: Roses, NOP

From: George and Paulette Mouchet <geomouchet_at_QNET.COM>
Date: Fri, 6 Jun 2003 20:08:14 -0700

Dear Kirk:

I don't believe the black spots have anything to do with bacteria. I
believe the black stuff is the byproduct of the fungal infection -- either
cellular byproducts (think cremation) or the fungus itself. I've sent a
note to a friend to try to clarify.

Meanwhile, here's what the ARS Consulting Rosarian Manual says about the
blackspot disease cycle:

"The fungus usually overwinters on infected leaves and canes as a mycelial
mat. As temperatures rise in the spring, the fungus produces conidia that
are moved by air currents or splashing water to new, developing and
expanding leaves, which are very susceptible. Conidia germinate under
conditions of free moisture and need free water conditions for at least 7
hours in order for infection to occur.

"As the infection develops, the leaf spot expands, taking on the
characteristic black appearance and producing conidia as a secondary
inoculum."

Since the blackspot fungus can easily overwinter, it's extremely important
to practice good sanitation in the garden, particularly when doing the
dormant pruning. The application of a dormant season horticultural oil
spray (like SunSpray horticultural oil) can be very effective in getting
rid of overwintering fungus.

During periods of active blackspot disease in the garden, good garden
sanitation can help prevent the spread of the disease.

I live in the high desert of California and I don't get blackspot because
there just isn't enough moisture for it. So, I can't say from experience
if AACT will prevent BS, but I believe it can. I would think you'd get the
best results if you applied AACT BEFORE the BS appeared. I'd apply as a
foliar spray and soil drench. When climate conditions are ripe for BS, I'd
foliar spray every week or so. Please note the BS fungus needs free water
for 7 hours in order to infect a plant. If you spray with AACT, you should
do so in the a.m. to allow enough time for your plants to dry out.

Hope this helps,
Paulette




-----Original Message-----
From: Kirk Leonard [SMTP:kirk_at_oregonatural.com]
Sent: Friday, June 06, 2003 9:16 AM
To: compost_tea_at_yahoogroups.com
Subject: [compost_tea] Re: Roses, NOP

Jeff -- The new congressional organic caucus is great news. Thanks for
sending. I have been led to believe OFRF is a quality organization, and
both Farr and DeFazio are as good as politicians get, imo...

Paulette, thanks for the correction. Is the black spot the actual fungus
or
does it trigger a bacterial reaction? Is it a black fungus? I've also
heard black spot over-winters in evergreens, which is why it keeps coming
back. Any truth to that? My roses are doing super this year with just one
nutrient tea soil drench (vermicompost, of course.:-) I must be lucky.

Kirk

> Message: 3
> Date: Thu, 5 Jun 2003 16:18:13 -0700
> From: George and Paulette Mouchet <geomouchet_at_QNET.COM>
> Subject: RE: Re: Roses, NOP Manure & CT
>
> Blackspot is caused by the fungus Diplocarpon rosae.
>
> Paulette
>





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Received on Fri Jun 06 2003 - 23:56:43 EDT

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