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Fabraea Leaf Spot

Leaf spot, caused by the fungus Fabrea maculatum, is a widespread and destructive disease of red tip (Photinia fraseri), loquat (Eriobotrya japonica), India hawthorn (Rhaphiolepis indica), some pear cultivars (Pyrus sp.) and several other members of the rose family. This disease is most damaging to plants in the landscape and nurseries during periods of cool, wet weather and when active growth is occurring.

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Symptoms

Tiny, circular, bright red spots on both the upper and lower surfaces of young expanding leaves are the first symptoms of Entomosporium leaf spot. Numerous small spots may coalesce into large maroon blotches on heavily diseased leaves. Leaf spots on mature leaves have ash brown to light grey centers with a distinctive deep red to maroon border. Tiny black specks, spore producing bodies of the fungus, can often be observed in the center of each leaf spot. Spots similar to those on the leaves can develop on leaf petioles and tender stem growth during prolonged periods of cool, wet weather.
Low levels of leaf spot usually cause little more than cosmetic damage but maintain a source of spores for future infections. Severe infections, however, often result in early and heavy leaf drop. Heavy leaf drop severely reduces the landscape value of red tip and can cause plant death. Some cultivars of India hawthorn are as severely affected as red tip.

Disease Cycle

Spots on the leaves and young shoots are important in the survival of the Entomosporium leaf spot fungus. Fallen, diseases leaves are less important sources of the fungus. Masses of spores are released during periods of wet weather from the fungal spore producing structures in the center of the spots from late winter through much of the year except during the hot periods of summer. These spores are spread to healthy foliage by a combination of splashing water and wind. New leaf spot symptoms appear within 10-14 days after a wet infection period.nfection Model: The four-celled conidia,with a distinctive insect-like appearance, are spread mainly from overwintering leaf litter, and some from twig cankers, by splashing water from rains or overhead irrigation. Wetting periods for infection may vary from 8 to 12 hours at temperatures of 10°C - 25°C.  Lesions begin to appear about 7 days after the beginning of an infection period. The disease may advance rapidly in late summer as wind and rain distribute the conidia throughout the tree. Susceptibility of leaves and fruit to infection does not decrease with maturity. Nearly all pears of European descent are susceptible to this leaf spot. The model is started when leaf wetness starts with rain. It stops when leaf wetness is disrupted for longer than 1 hour.

(c) Dr. Heinrich Denzer, Pessl Instruments GmbH, Weiz, 2008