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Rose Black Spot Disease

Rose Black Spot Disease


A common disease of Roses, called Black Spot Disease , is caused by the fungus Diplocarpon rosae. This fungus attacks young expanding leaves. Fungal spored which were formed on infected fallen leaves or on canse are splashed to the new lower leaves of roses in the Spring by rain or sprinkler irrigation. The spores must remain wet for several hours in order for the spore to germinate and invade the leaf. If temperatures are warm following infection, symptoms may become visible in 3 days. New spores can form in as few as 10 day after infection. Thus under some conditions the fungus can infect a plant, begin producing new spores, and spread to other leaves within two weeks.

Black Spot SymptomsBlack Spot Disease on Rose Shrub

Leaves - Dark spots up to 1/2 inch in diameter have "feathery" edges when some rose cultivars are infected. Spots are smaller with more distinct edges in other cultivars. These spots may have a yellow halo surrounding them. Infected leaves yellow and fall.

Canes - Small purplish spots form on the current year's growth.




Black Spot Management

Because the fungus spore must have free water on the leaf or cane in order to germinate and penetrate, take steps to insure that plant surfaces dry quickly or are not wet.

  1. Maintain good weed control so that air circulation around the plant is good.
  2. Avoid wetting the plants when irrigating
  3. If plants are misted or sprinkler irrigated, only do so when the plant surface will dry quickly. 

Because the fungus survives from year to year in infected material;

  1. Rake and destroy fallen leaves.
  2. Prune out areas that have symptoms of Black Spot Disease
  3. ZeroTol Fungicide/Bactericide is a ready to use spray that provides immediate disease control for Black Spot on Roses. It can be used as a preventative or curative application. ZeroTol Ready to Spray leaves no chemical residues behind, making it the natural choice for use around children and pets. BUY ZEROTOL NOW!


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