Key Facts
• Mid-March onward: Ascospores intermittently dispersed from infected fallen leaves.
• Late March: Sharp increase in spore dispersal, exceeding average levels.
• Conidiospore dispersal from flower cluster bases also increased during this period.
• Flower bud exposure to petal fall is a highly susceptible stage for pears.
• April 2: Hiroshima Meteorological Observatory forecasts favorable weather for disease spread over next month.
• Tottori Pest Control Office issued first 2026 pest forecast warning on April 7.
• Recommended control measures include following local schedules, spraying early mornings with low wind, and thorough treatment from bloom start to petal fall.
• Avoid spraying during pollination to protect pollinators.
• Monitor flower clusters for black lesions; immediately remove and dispose of infected parts.
• Additional spraying advised if rainfall is heavy or spray intervals extend.
Summary
The Tottori Prefectural Pest Control Office warns of a potential widespread outbreak of pear black spot disease across the prefecture in 2026. Since mid-March, spore dispersal from overwintering infected leaves and flower cluster bases has been higher than usual, with a notable surge in late March. The critical period for infection is from flower bud exposure through petal fall, when pears are most vulnerable. Weather forecasts predict conditions favorable for disease development in the coming month. To mitigate spread, growers are urged to adhere to local control calendars, spray during calm early mornings, and focus treatments during the flowering period while avoiding pollination times to protect beneficial insects. Visual inspection for black lesions on flower clusters is essential, with immediate removal and disposal of infected tissues recommended. Additional treatments should be considered following heavy rains or prolonged intervals between sprays. These measures aim to reduce the impact of this damaging disease on pear production in Tottori Prefecture.
