fungi

**"Mary C. Weaver" mcweaver@bellsouth.net>**

Joanie wrote:

>One more question about black spot and powdery mildew: do young roses tend to
>be more susceptible to these diseases?

No. The healthier the rose, the better it will do, although the vast 
majority of roses will have problems with blackspot or powdery mildew 
if environmental conditions are right. Blackspot is predominant in 
climates with lots of rainfall because the spores can't germinate 
unless the foliage remains wet (note: humidity has nothing to do with 
it) for at least 7 continuous hours. Hence the warnings about not 
watering from above and not watering late in the day. Powdery mildew, 
on the other hand, is discouraged by the presence of water on leaves 
and tends to be more of a problem in dryer climates.

How do you encourage health? Plant the roses in good soil with plenty 
of organic matter. Make sure they have plenty of sun--most prefer at 
least six hours a day--and are not shaded in the morning (in order to 
avoid blackspot, you want the dew to be dried by the sun). Give them 
plenty of water and adequate fertilizer. Buy healthy plants in the 
first place. Maintain good hygiene in the flower beds, raking up 
diseased fallen leaves.

>Should I give these youngsters (grade
>1, two year old plants, planted spring of '00) another year using only
>detergent and baking soda to counter the effects of the diseases?

Baking soda is not effective against blackspot--only against mildew. 
If you live in a wet climate and don't want to spray, I'd stick to 
the most disease-resistant roses: hybrid rugosas, hybrid musks, 
albas, many of the modern shrubs (e.g., those hybridized by Griffith 
Buck, the House of Meilland, etc.), some of the gallicas and 
polyanthas, etc.

I recently wrote an article for hgtv.com on a dozen easy-care roses. 
If people are interested, I'll post the link when the article goes up.

Cheers,
Mary W.

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Mary C. Weaver
Author, Roses: A Growing Guide for Easy, Colorful Gardens (Macmillan, 1998)
mcweaver@bellsouth.net or maryweaver@mac.com

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