Blackmold Disease Control

Gene Miyao, Farm Advisor, Yolo/Solano/Sacramento Counties

Anticipating wet weather? In the Sacramento Valley, fungicide applications are targeted on fields to be harvested in mid September or later when threat of rainfall increases and morning dews contribute to fruit rot activity.

Blackmold fungicide trials conducted in our local area generally showed:

• Preventive applications about 4 to 6 weeks before anticipated harvest reduced mold levels.
  

• Fruit rot levels were reduced about 50% compared to non-treated controls.
  

• Single applications were sufficient under moderate disease pressure.

Preventive timing is critical. In a field test with ripe fruit at UCD, an application made 12 hours after rainfall was not effective in reducing blackmold. Coverage may also be important.

Fruit maturity is clearly a factor in disease development. Fruit are susceptible to blackmold when ripe. The most susceptible fruit are the over-ripe ones. Sunburn damage also increases risk to blackmold. Timely harvest to limit the level of overripe fruit is helpful when blackmold conditions are favorable.

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