Aug 30, 2024

Charcoal rot emerges in California processing tomatoes

An unusually hot summer has led to the appearance of charcoal rot in some California processing tomato fields.

The observation signals a potential concern for local vegetable growers, according to the most recent University of California Cooperative Extension (UCCE) Agricultural and Natural Resources Kern County vegetable crop update.

Charcoal rot, caused by the soilborne fungus Macrophomina phaseolina, has historically been a minor issue but could become more problematic with rising temperatures.

The fungus, which thrives in high temperatures and water stress, affects more than 500 plant species across more than 100 families.

Charcoal rot is characterized by greyish-black discoloration on roots and stems, wilting, stunting, and chlorosis of lower leaves, eventually leading to plant collapse.

While the disease has so far been of minor importance, its increasing prevalence due to warmer summers suggests it could become a more significant challenge, according to UCCE’s update.

Current management strategies include rotating crops with non-host plants, though this is limited by the pathogen’s wide host range. Other practices such as timely irrigation, destruction of infected debris, and cleaning equipment between fields may help mitigate the impact.

UCCE has advised growers to contact local farm advisors for official diagnoses if charcoal rot is suspected. For more information or assistance, Jaspreet Sidhu, farm advisor for vegetable crops at UCCE, can be reached by phone 661-304-8870 or via email.

Read the crop updates here.