may be exposed on the edges or on the inner surface of the carpel if the ovary becomes leaf-like. If the ovule is affected by phyllody, it develops separately from the rest of the carpel. The best known example of phyllody of the carpels is found in the Japanese cherry (Prunus serrulata), in which one or both of the carpels can become leaf-like (although the distal half of the style and the stigma are usually unaffected). Incidentally, some Japanese cherry cultivars also exhibit "doubling" of the petals due to petalody, where a second corolla develops instead of stamens. Causes Biotic In many cultivated plants, phyllody is caused by infections of plant pathogens and/or infestations of ectoparasites. Aside from exhibiting phyllody, they may also exhibit other symptoms like virescence, witch's brooms, chlorosis, and stunted growth. Examples of these biotic factors include: Phytoplasmas - specialized prokaryotic microorganisms that cause more than 200 distinct plant diseases. They resemble other bacteria but lack cell walls and are filamentous or pleomorphic in form. They are obligate parasites of plant phloem tissue and are spread by insect vectors. They are the most common cause of phyllody. Evidence suggests that phytoplasmas downregulate a gene involved in petal formation, instead causing leaves or leaflike structures to form. Examples of commercially important phytoplasma diseases are aster yellows, apple proliferation, clover phyllody, and Sesamum phyllody. Viruses, like the rose rosette disease (RRD) Fungi, like the smut fungus Sphacelotheca reiliana of corn and the rust fungus Atelocauda koae which infects Acacia koa Water molds, like Sclerophthora macrospora which infects more than 140 kinds of cereals including rice, corn, and wheat. The disease is more commonly known as "crazy top" because its most striking symptom is phyllody of the ears and tassels. Insect damage In addition to causing phyllody itself, insects and other ectoparasites also serve as disease vectors that can spread phyllody to other nearby plants. The most common of these insect vectors are leafhoppers, an example of which is Hishimonus phycitis, which transmits the phytoplasma-caused little leaf phyllody in eggplants. The broken-backed bug (Taylorilygus apicalis) is another insect vector of a phytoplasma-caused phyllody in species of Parthenium. Other ectoparasite vectors include eriophyid mites, like the rose leaf curl mite (Phyllocoptes fructiplilus) which is known to be the primary vector of the rose rosette disease; and the chrysanthemum rust mite (Paraphytoptus chrysanthemi) which transmits phytoplasma-caused phyllody in species of chrysanthemums. Abiotic