The pathogen that causes bacterial spot is very good at what it does. Forming small lesions on the rinds of pumpkins, melons, cucumbers, and other cucurbits, it mars the fruits’ appearance and ushers in secondary pathogens that lead to rot and severe yield loss. The bacterium, Xanthomonas cucurbitae, is so successful that it has had no reason to evolve through time or space. 

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