roses diseases - Knowledgebase Question

Victorville, Ca
Question by ruiz92395
June 17, 2008
I think my roses have a disease call BOTRITIS but I'm not sure.Can you show me some pictures about that and how treat it?

Answer from NGA
June 17, 2008


I don't have photos of botrytis, but I can give you a pretty good description: Rose flowers and buds will have a gray-brown fuzzy growth. The fungus is most active when temperatures are 62 to 72 ?F and conditions are moist. Infected canes have discolored, sunken areas (cankers) and dieback that can extend down the stem from the flowers. Diseased flower petals have small, light-colored spots surrounded by reddish halos, which can quickly expand into large, irregular blotches. Buds fail to open and often droop. Thrips can cause similar damage to half-open buds, so inspect plants carefully.

Prevention and Treatment: Keeping the area clean is more important than anything else. Collect and discard all fading flower blossoms and leaves. Provide good air circulation, and avoid wetting the leaves when watering. Disease easily develops on canes that have been damaged and canes that are kept too wet by a manure mulch or wet leaves. If chemical control is necessary, fungicides containing captan, chlorothalonil or neem oil (clarified hydrophobic extract) are available for homeowner use. Apply all chemicals according to directions on the label.

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