Indian hawthorns (Rhaphiolepis spp.) are compact evergreen shrubs or small trees prized across U.S. Department of Agriculture plant hardiness zones 8 through 11 for their neat form and clusters of fragrant pink or white flowers that appear in spring. A handful of diseases can potentially bother this plant, although good cultural care practices will prevent or minimize the impact of most disease problems.
Entomosporium Leaf Spot
Entomosporium leaf spot, generally the most prevalent disease to afflict Indian hawthorn, is caused by fungi within the genus Entomosporium. This disease appears on older leaves as tiny reddish leaf spots sometimes surrounded by a yellow halo. Spots become darker and expand, and white masses of spores may develop; leaf drop also occurs. The fungus spores spread in splashing water, so avoiding overhead watering and pruning branches out to improve air circulation can limit this disease. Good sanitation is also important, including removing and disposing of infected or fallen leaves and replacing ground covers under the hawthorn with mulch. Where the leaf spot has proven very problematic in the past, a preventative treatment with chlorothalonil or a copper compound may be warranted.
Fire blight, caused by the bacterium Erwinia amylovora, appears on Indian hawthorn branches as cankers that produce a light tan bacterial ooze that eventually darkens. Splashing water or insects transmit the bacteria to blossoms or shoots. Affected shoots, leaves, flowers and fruit turn black and die but can remain on the plant. Pruning out infected wood in summer or winter, avoiding irrigation when the Indian hawthorn is in bloom, and avoiding heavy pruning or overfertilization that stimulate vulnerable new growth will limit the spread and impact of this bacterium.
Phytophthora Collar and Root Rot
The soilborne fungus Phytophthora can cause collar and root rot in Indian hawthorn. This disease generally only affects plants in warm, poorly drained soil. The leaves on infected plants appear wilted or drought-stressed, and dark oozing areas may appear on the bush near the soil line. Good soil drainage and water management are crucial for Phytophthora prevention.
Powdery mildew fungi appear as white powdery growth on Indian hawthorn leaves, shoots and sometimes flowers. New growth may appear distorted, and infected leaves tend to drop prematurely. The powdery mildew fungus spreads by wind and prefers shady conditions and a temperature between 60 and 80 degrees Fahrenheit. To avoid or address problems with powdery mildew, plant the Indian hawthorn in full sunlight; space bushes to allow for excellent air circulation; avoid the use of excessive or fast-release fertilizer; and, if necessary, apply sulfur to prevent the disease or horticultural oil to address an infection.
Verticillium wilt, caused by a fungus of the same name, affects an Indian hawthorn's vascular system, causing foliage discoloration, wilt and dieback that often begins in scattered portions of the plant or on one side. When bark is peeled back, infected wood has dark staining. Providing the Indian hawthorn with the best care, including proper irrigation and fertilizer, can encourage healthy new growth and bush survival.
- University of California Statewide Integrated Pest Management Program: Rhaphiolepis, India Hawthorn -- Rhaphiolepis spp.
- University of California Statewide Integrated Pest Management Program: Entomosporium Leaf Spot
- University of Florida IFAS Extension: Indian Hawthorn
- University of California Statewide Integrated Pest Management Program: Phytophthora Root and Crown Rot in the Garden
- University of California Statewide Integrated Pest Management Program: Fire Blight
- University of California Statewide Integrated Pest Management Program: Powdery Mildew on Ornamentals
- University of California Statewide Integrated Pest Management Program: Verticillium Wilt -- Verticillium spp.
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