Seventy isolates of Mycovellosiella nattrassii, collected from eggplants in Kochi Prefecture, Japan, were tested for sensitivity to strobilurin fungicides in 2000. The frequency distribution of minimum inhibitory concentrations of azoxystrobin against mycelial growth had two distinct peaks at 3.13ppm and over 1600ppm, considered to be sensitive and resistant, respectively. Isolates resistant to azoxystrobin had cross resistance to kresoxim-methyl. The EC50 of azoxystrobin and kresoxim-methyl for mycelial growth and the inhibitory rate of conidial germination by azoxystrobin were also clearly distinguishable between resistant and sensitive strains. Control efficacy of these two fungicides was very low against resistant strains in an inoculation test.
A selective medium (designated as NSVC-In medium) was developed to isolate of Erwinia ananas, the causal agent of bacterial palea browning of rice. Medium NSVC-In contains per 1000ml of distilled water: 10g inositol, 10g peptone, 50g NaCl, 100mg vancomycin, 100mg cycloheximide, and 15g agar. The medium is adjusted to pH 6.8 with NaOH before autoclaving. Plant pathogenic E. ananas grew well on this medium to develop characteristic colonies, but the growth of nonpathogenic E. ananas and Erwinia herbicola was inhibited. Plating efficiency of this medium for pathogenic E. ananas was the same as that of nutrient agar medium. Pathogenic E. ananas could be selectively detected from dead leaves of rice plants.
Pathogens causing cymbidium yellow spot produced conidia on rape seed oilcake used as fertilizer. These conidia, as well as those produced on lesions of leaves, were the inoculation source. When plants with lesions were sprinkled with water, the pathogens increased a hundredfold on rape seed oilcake. Both types of conidia were dispersed in the wind by mist from a wind tunnel. Greenhouse experiments revealed that watering from the top of the plants also promoted fungal dispersal.