Wheat spikes, grown in a field that received only natural dew- and rainfall or in a plastic greenhouse that received water from a sprinkler system, were inoculated with a deoxynivalenol (DON)-producing Fusarium graminearum species complex to test the relationship between wetness duration after inoculation and subsequent DON concentration. When wetness duration, measured with a wetness sensor, exceeded 150 h, DON concentration increased with increasing durations of wetness. Wetness duration can thus serve as an index to predict the beginning of DON accumulation. In the field, accumulation of DON was related not only to rainfall but also to wetting by dewfall.
Sensitivity to strobilurin fungicides was tested for 107 isolates of Colletotrichum gloeosporioides, obtained in 2009 and 2010 from mangoes with anthracnose in Okinawa Prefecture, Japan. When isolates were grown on potato dextrose agar containing 1000 ppm of salicylhydroxamic acid and various concentrations of azoxystrobin and kresoxim-methyl, two strains showed a minimal inhibitory concentration of >3000 ppm and were regarded as resistant. The control efficacy of azoxystrobin against two strains was low in a leaf bioassay, and the G143A point mutation in the cytochrome b gene, conferring resistance to strobilurins, was confirmed by PCR-RFLP using restriction enzyme Fnu4HI.