Flowers, leaves and stems were severely rotted on common garden petunia, Petunia×hybrida Vilm., in a glass house in Tokyo Metropolis in August 1995. Flowers with water-soaked lesions at an early stage wilted and rotted. Calyces, stems and leaves developed water-soaked, dark-green lesions, then rotted. Whitish mycelia and monosporous sporangiola were produced on the rotten plants. Sporangiola of the pathogen, were also observed on subirrigation mats and fallen flowers. A fungus exclusively isolated from lesions produced white to pale yellowish brown mycelia with scattered monosporous sporangiola on PDA plates. Inoculations with sporangiola reproduced the symptoms on its original host as well as on garden pea and four-o'clock. The same fungus was reisolated from the inoculated plants. The fungus produced monosporous sporangiophores and monosporous sporangiola abundantly on PDA. Zygospores were produced in dual culture with an authentic mating type isolate of Choanephora cucurbitarum (Berkeley & Ravenel) Thaxter. The causal fungus was identified as C. cucurbitarum based on morphology and mating tests. The fungus grew on PDA plates at 10-40°C with an optimum at 30°C. This paper represents the first report of C. cucurbitarum on common garden petunia causing a disease referred to as Choanephora blight.
Isolates of Mycovellosiella nattrassii isolated from greenhouse-grown eggplants were tested for sensitivity to triflumizole in June 1998 because the effectiveness triflumizole in controlling leaf mold of eggplant in Saga Prefecture appeared to have declined in recent years. All 100 isolates were resistant to triflumizole with EC50 values ranging from 0.0651 to 24.1μg/ml. Both the preventive and curative effects of triflumizole for controlling leaf mold decreased when eggplant was inoculated with the most resistant isolate. The resistant isolates were also cross resistant to the DMI (sterol demethylation inhibitors) fungicides, fenarimol and myclobutanil. The resistance of isolates against triflumizole increased after successive applications of fenarimol or myclobutanil in the greenhouse. Survival of conidiospores of highly resistant isolates was lower than that of sensitive isolates after a heat treatment of 35-40°C for 10-20 days in the greenhouse.
Anthracnose of netted melon (Cucumis melo var. reticulatus Naud.) which appeared on leaves, petioles, stems and fruits was observed in Miyagi prefecture in 1997. The causal fungus was isolated from the netted melon and identified as Colletotrichum orbiculare (Berkeley & Montagne) Arx, based on its morphology, growth temperatures, and pathogenicity. Inoculation experiments revealed that 17 species plants belonging 10 genera of Cucurbitaceae and six species of plants belonging to six genera in three other families were infected by the pathogen. This is the first report of anthracnose of netted melon caused by Colletotrichum orbiculare in Japan.