unique black spot question

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shoy
Posts: 38
Joined: Wed Dec 31, 1969 7:00 pm

unique black spot question

Post: # 73236Post shoy
Tue Aug 17, 2021 3:52 pm

I am observing something re: black spot resistance that I don't fully understand. I've kept several roses I purchased as bands (now potted up) under my car port. None of them, including 'Colette Clement,' has gotten any black spot this year. Roses growing in the yard that are susceptible do have black spot infection, i.e. 'Dainty Bess.' For years, I've grown 'Alister Stella Gray' under the eve of my front porch. It rarely shows any black spot infection even though pressure is very high here in 8b central GA.

Any thoughts?

Stephen
Stephen Hoy
Singularly Beautiful Roses
Warner Robins, GA

roseseek
Posts: 5279
Joined: Sun Dec 11, 2011 6:54 pm
Location: Zone 9b Central California, Sunset Zone 15

Re: unique black spot question

Post: # 73237Post roseseek
Tue Aug 17, 2021 11:58 pm

Heat/sun stress? I am finding struggling plants rebounding like gang busters when moved under the eaves of the patio cover so they receive strong reflected light instead of the direct, hot sun. And, I'm not in the desert nor are we dealing with triple digits, but ocean breezes and quite temperate "heat". It's as if the sun is inhibiting their growth, health and performance.
Kim
California Central Coast
USDA Zone 9b
Sunset Zone 15
Cooler inland coastal valley with strong marine influence

bvanderhoek
Posts: 163
Joined: Wed Dec 14, 2011 4:19 pm

Re: unique black spot question

Post: # 73238Post bvanderhoek
Wed Aug 18, 2021 9:19 pm

We've had a lot of rain this summer, which leads to heavy morning dews. Would keeping the plants under a roof keep the dew from the leaves, and therefore keep fungal spores from taking hold? Just an idea based on the fact that my car, parked on the gravel, is covered with dew every morning, while my husband's car in the carport stays dry.

roseseek
Posts: 5279
Joined: Sun Dec 11, 2011 6:54 pm
Location: Zone 9b Central California, Sunset Zone 15

Re: unique black spot question

Post: # 73239Post roseseek
Wed Aug 18, 2021 9:53 pm

I had always read it was the presence of humidity rather than physical water that induced the spores to germinate. I never had disease issues when I set the oscillating sprinklers to water the roses over head as if it was raining. The foliage was huge and completely healthy. Issues occurred during periods of extreme aridity (water stress) and periods of sustained, increased humidity. I'm also finding buds inserted into Pink Clouds exploding into growth quite quickly under the patio cover in strong light but with out any direct sun. It's performance I would expect from green house grown plants.
Kim
California Central Coast
USDA Zone 9b
Sunset Zone 15
Cooler inland coastal valley with strong marine influence

jbergeson
Posts: 1422
Joined: Thu Dec 15, 2011 11:54 pm

Re: unique black spot question

Post: # 73245Post jbergeson
Fri Aug 20, 2021 7:45 am

I keep some roses in pots on a drip system in a greenhouse. It is a hoophouse with a single layer of poly and sides that stay rolled up. My roses in there never show signs of blackspot or leaf spot, although they can get mildew.

shoy
Posts: 38
Joined: Wed Dec 31, 1969 7:00 pm

Re: unique black spot question

Post: # 73248Post shoy
Sat Aug 21, 2021 4:29 pm

Joe;
I might try this for my single HT collection. On the other hand will my roses be missing out on the benefits of natural rain?
Stephen
Stephen Hoy
Singularly Beautiful Roses
Warner Robins, GA

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