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Plant Disease Profile: Rose blackspot

15 July 2012
Plant Disease Profile: Rose blackspot

This plant disease's name is very descriptive and very apt. The rose blackspot is a fungus which grows on your roses. This fungus produces dark spot marks on rose stems and leaves. The plant's leaves will turn yellow and fall off before autumn arrives. Sadly, winter doesn't kill this fungus since its spores will overwinter on roses' fallen leaves. As a result, it can reinfect the plant come spring as the rose's new foliage comes in.

The rose blackspot does not directly kill roses. However, it can greatly weaken a rose-especially if the blackspot occurred very early in the season.

Organic solutions to blackspot

Make sure to keep your roses' surroundings clean. Always pick up and dispose of fallen leaves. Cut out any blackspot stems as you prune. During late winter, make sure to put a thick layer mulch around infected plants' base so rain can't splash spore-infected soil to the plants' new growth in the spring. Also, pick blackspot-resistant rose varieties.

Chemical solutions
Use fungicide. Apply to new foliage during early spring. Follow up with further sprayings spread out in regular intervals.