Leaf Spots

    Leaf Spots

    Many fungi and bacteria

    leaf spot

    Leaf spot on roses (Ward Upham, Kansas State University, Bugwood.org)

    leaf spot

    Septoria leaf spot (North Carolina State University Department of Plant Pathology)

     

    Hosts, Symptoms & Signs

    • caused by many fungal and bacterial pathogens
    • affects all ornamentals
    • leaves start to develop brown to black spots in varying sizes
    • in some cases, the brown areas will fall out leaving a hole behind
    • in some cases (i.e., black spot on roses), infected leaves will turn yellow and fall off

    Disease Cycle

    • overwinter in fallen leaves or diseased branches
    • spores land on leaves and germinate during moist conditions and colonize the leaf
    • fruiting structures develop on lesions; spores spread from lesions during wet conditions, colonizing new areas of the same, or nearby leaves
    • bacteria from lesions are washed across the leaf and enter new leaves through openings like stomates or small wounds

    IPM Recommendations

    • Rake and remove leaves in the fall.
    • Apply fungicides and bactericides like copper to prevent the spread to uninfected leaves; these will not cure infected leaves.
    • Avoid wetting leaves with irrigation.