Black Spots On Rose Leaves And Brown, Shriveled Roses Blossoms - Knowledgebase Question

Chesapeake, VA
Avatar for thorneandt
Question by thorneandt
May 29, 2001
What is the best product to use on my hybrid, antique, climbing and english roses (19 varieties in my back yard) to get rid of black spots on my rose leaves? All of them have it. Should I use soap & water and if so, what is the mixture? Is Ortho the best way to go? I'm confused by all the products available so I thought I'd ask the experts. Does the black spot have anything to do with the full bloom roses shrivelling up and turning brown every time it rains really hard? They look like they had the life literally sucked out of them overnight.

Thanks for your assistance.

Answer from NGA
May 29, 2001
Based on your description it sounds like your rose problem is "black spot" although there may also be a separate fungal problem with the blossoms, although then and again some varieties will simply do that in wet weather.

A fungus causes black spot on roses. Some cultural
practices may be helpful in controlling it. These include
planting varieties resistant to it, ensuring your plants are in a
location with good air circulation, avoiding wetting the
leaves when watering, and cleaning up, removing and
destroying any infected leaves. Do this especially well each
fall to minimize reinfection from year to year. Each winter, you might even try handpicking off any remaining leaves from the bushes. Also, pruning correctly to ensure good air circualtion and light reaching the interior of the plant can also be helpful.

A clean layer
of organic mulch (such as shredded bark or half finished
compost or chopped leaves) applied before the plants leaf
out again in spring should also help prevent reinfection. It keeps rain from splashing it back up onto the plants.

Neem oil may also be helpful. Neem controls
aphids and mites on your roses, and the oil version of neem
also will control powdery mildew and black spot.

Some gardeners have had success using baking soda and
water sprays to control black spot. Tests in England
indicated that 1.5 tablespoons of baking soda in 1 quart of
water was effective. Add just a a few drops of dish detergent to
help it stick. You may want to try it and see for yourself.

CAUTION: Always test something new like this on a few leaves and
wait a few days to see the results before spraying the rest of each plant.

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