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Black rot, leaf spot and canker Botryosphaeria obtusa Sphaeropsis malorum [anamorph] Black spot (of Japanese pear) Alternaria alternata. Blister canker Helminthosporium papulosum. Blister disease Coniothecium chomatosporum: Blue mold rot Penicillium spp. Penicillium expansum. Botrytis spur and blossom blight Botrytis cinerea
On the apple tree, the infections occur on leaves, fruit and young twigs. [4] The brightly colored spots produced on the leaves make it easy to identify. Small, yellow-orange spots appear on the upper surfaces of the leaves, anytime from April to June. [5] These spots gradually enlarge and turn orange or red and may show concentric rings of color.
Gymnosporangium libocedri, the Pacific Coast pear rust, is a plant pathogen and rust fungus. [1] It produces orange gelatinous growths ( telia ) on incense cedar in the spring. Its secondary hosts include apple , crabapple , hawthorn , mountain ash , pear , quince , and serviceberry .
Spores produced from the fungus-induced swellings on juniper stems can be infectious up to 6 km. The disease causes a yellow-orange spot that turns bright red on leaves of pear trees. The disease can be particularly damaging on pear, resulting in complete defoliation and crop loss if not treated.
The most common cause of bacterial leaf spots are by bacteria in the genera Pseudomonas and Xanthomonas. For example, Pseudomonas syringae pv. tabaci is known to cause angular leaf spots of cucumber, Pseudomonas syringae pv. phaseolicola to cause bean leaf spot and Xanthomonas campestris pv. phaseoli, angular leaf spot of cotton. [7]
Fire blight on a pear tree caused by Erwinia amylovora. Tissues affected by the symptoms of Erwinia amylovora include blossoms, fruits, shoots, and branches of apple (Pomoideae), pear, and many other rosaceous plants. All symptoms are above ground and are typically easy to recognize.
Most commonly Cephaleuros virescens is identified by the leaf spots it causes. Theses leaf spots are an orange-brown rust in color and usually occur entirely on the upper leaf surface, although leaf spots on the undersides of infected leaves have been reported. The spots are fuzzy in texture and approximately 2 cm (0.8 in) in diameter. [2]
Chondrostereum purpureum is a fungal plant pathogen which causes Silver leaf disease of trees. It attacks most species of the rose family Rosaceae, particularly the genus Prunus. The disease is progressive and often fatal. The common name is taken from the progressive silvering of leaves on affected branches.