Roses with black spot - Knowledgebase Question

Spokane, Wa
Question by erinmlocke
June 30, 2010
I live in Spokane, WA and I have 40 roses that have yellow leaf and black spot. I sprayed them in the spring and again last week and I cannot control it. It is destroying them. They are bush roses.
What can I feed them to stop this because the spraying is not working.
HELP!!!


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Answer from NGA
June 30, 2010

0

A fungus causes black spot on roses. Some cultural practices may be helpful in controlling it. These include planting varieties resistant to the disease, ensuring your plants are in a location with good air circulation, and avoiding wetting the leaves when watering. Do not water in the evening, water early in the day so no moisture sits for very long on the foliage. Clean up and destroy any infected leaves, especially in the fall to minimize reinfection from year to year. Use a dormant spray that includes lime sulfur. A dormant spray smothers insect eggs and disease organisms before they get started. Apply the spray right after you prune in late winter. Other remedies include neem oil, and the fungicide triforine. Be sure to read and follow the label instructions. A clean layer of organic mulch (such as shredded bark or chopped leaves) applied before the plants leaf out again in spring also helps prevent reinfection. The mulch helps keep fungal spores from splashing up onto the plant and the new foliage. I hope this helps.



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