Yesterday we began discussing the many disease problems which can affect your roses. We covered how to diagnose and treat three different disease problems such gall, powdery mildew and downy mildew. Today we are going to talk about three more diseases which are common in roses and how to treat them.
Symptom: Yellow blotches on upper surfaces of leaves, small powdery orange or black postules on underside of mature leaves.
Cause: Rust—This is a fungal disease that may appear when days are warm and nights are cool and moist.
Treatment: Ensure that the rose plants have good air circulation and ample sunlight. If further treatment is necessary, you will need to treat with a fungicidal treatment that is listed for rust control.
Symptom: Brown dieback of cut canes; brown fuzzy mold on debris around the rose plant. In severe cases, the entire flower bud rots.
Cause: Botrytis blight (grey mold)—This fungal growth favors rainy cool periods or nights with high humidity.
Treatment: Remove all of the damaged areas of the rose plant and clean up leaves and debris from below the plant to prevent the fungus from spreading. Maintain good air circulation around your roses.
Symptoms: Dark black spots with irregular edges on the leaves. The spots tend to be round, varying in size from pinpoint to quarter-sized. Half of leaf yellows or leaf drops completely from the rose plant.
Cause: Black spot—This fungal disease favors rainy weather, poor air circulation or improper watering.
Treatment: Spray-Dust-Watering technique. After winter pruning, apply a dormant lime-sulphur spray. Remove dropped leaves and other debris. During the growing season, spray with fungicides listing rose black spot as a target on a rotational basis. Fungus spores are found on the undersides of leaves, so spray upward from underneath the rose plant. Spray in the early morning when the weather is calm and cool. Water your roses early to allow the foliage to dry thoroughly.
Now that you know some of the most common disease problems in roses, which ones have you had experience with? What have you done to control or eradicate the disease? Leave me a comment and share.
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