4. Effect on the initial stage of the life cycle of Botrytis cinerea

Ten microliters of conidia (1.0×10⁵ spores/mL) suspended in potato sucrose liquid medium was dropped on 3% agar medium amended with fungicide. Fungicide-treated spores were incubated at 20°C under light conditions in the laboratory. Investigation was performed 20 hr after treatment. One hundred conidia per plot were observed under light microscope, and germ-tubes below 50 µm were counted. Tests were conducted 3 times, consisting of two replicates per plot. Percent inhibitions of conidium germination and germ-tube elongation were calculated.

Effect of aminopyrifen on infection process of B. cinerea on cucumber cotyledons was examined. Solutions of aminopyrifen SC and M006 were sprayed on the whole plant. One day after treatment, 5 µL of conidial suspensions (1.0×10⁵ spores/mL) were dropped onto the upper side of cucumber cotyledons, and inoculated plants were kept in a humid condition of 20°C. The inoculated part of the cucumber cotyledon was cut into 5 mm squares 6, 24, and 48 hr after inoculation. The tissue was fixed and decolorized by immersing into a formalin-acetic acid-alcohol solution (36.0–38.0% formaldehyde: 99.7% acetic acid: 99% ethanol=1 : 1 : 1). The observation was conducted under a light microscope after staining with 0.1% methyl blue.