Alternaria Leaf Spot

Editorial diagnosis

Diagnosis overview

Alternaria leaf spot causes dark, often ringed spots on brassicas.

In gardens, Alternaria Leaf Spot can occur on plants including Lacinato kale, red cabbage. In the available profiles, it is linked mainly with Cabbages, Leafy vegetables.

Its importance depends on how quickly it spreads and whether seedlings, shoot tips, flowers, or fruit are affected. Conditions that favour it include Wet weather or prolonged leaf wetness, Dense planting and poor airflow, Susceptible cultivars. It becomes serious when leafy brassicas become unusable.

Compare upper and lower leaf surfaces, the boundary between healthy and damaged tissue, and spread after wet weather. Coatings, spores, or progressive rot support a disease diagnosis.

A common mistake is to identify a disease from one spot alone; weather, spread, and pathogen structures also need to fit.