Phyllosticta

Phyllosticta Leaf Spot is an aggressive fungal disease caused by the pathogen *Phyllosticta*. Forms light brown to tan lesions with no particular orientation or pattern. Often the lesions are boarded by a darker brown line and pycnidia fruiting bodies are uniformly distributed. Lesion can generally grow larger than either Phoma or Phomopsis, easily confused with both. If left unchecked, it poses a significant threat to the infected plant and can quickly spread to surrounding collections.

To manage and prevent the spread of *Phyllosticta*, the following cultivation adjustments are recommended: * Isolation: Immediately isolate any infected plants showing active signs of spreading lesions. * Fungicide Protocol: Apply systemic and contact fungicides. Alternate applications of thiophanate-methyl and azoxystrobin, or use Mancozeb, to prevent the pathogen from developing resistance. * Substrate Optimization: Verify that the media pH is within the appropriate range for Trichocereus and ensure the soil has excellent drainage. * Nutritional Support: Supplement the fertilizer regimen with additional calcium, magnesium, and potassium to bolster the plant's natural immune defenses.