Mayhaws are native species of hawthorn that are popular in Mississippi and the Deep South for their small, edible, apple-like fruits that can be transformed into jellies, preserves, and syrup. Mayhaws (Crataegus aestivalis, C. opaca, or C. rufula) are in the rose family (Rosaceae), which also includes apples, and are prone to similar disease problems. Because mayhaw is a less commercially popular fruit than its apple cousin, there are fewer options for disease resistance and chemical control. This publication discusses the most common disease problems encountered on mayhaws in the Southeast.

Rust Diseases (quince rust and cedar apple rust) Mayhaws are susceptible to quince rust and cedar apple rust. Although caused by two different species of the fungus Gymnosporangium, both rusts produce similar symptoms and signs on mayhaws. Symptoms and Signs Twigs, fruits, thorns, petioles, and leaves of mayhaws may be infected by rust fungi. Symptoms are visible about 7–10 days after infection. Fungal infection causes cells to grow abnormally large (hypertrophy), giving plant tissue a swollen appearance. Infected mayhaw twigs have spindle-shaped swellings. Leaf veins, common infection sites, swell and diseased leaves curl and die. Infected fruit appear covered with white, tube-like projections about 2– 3 millimeters long. Each white tube splits open lengthwise, revealing orange spores on the fruit surface (Figure 1). Spore stages of the fungus are produced on infected twigs, fruits, petioles, and bases of thorns. Infected tissue typically dies after spore production, resulting in twig dieback. Ecology and Spread All rust fungi are obligate parasites, meaning that they can only survive on a living plant. The quince rust fungus has a very complicated life cycle and needs to spend part of its life on a juniper or red cedar and part of its life on a plant in the rose family to complete its life cycle. Susceptible plants in the rose family are listed in Table 1.

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