Peppery Leaf Spot

Peppery leaf spot is caused by Pseudomonas bacteria and is a major pest of brassicas. They do not penetrate directly into plant tissue but need to enter through wounds or natural plant openings. Wounds can result from damage by insects, other pathogens, and tools during operations such as pruning and picking. Bacteria only become active and cause problems when factors are conducive for them to multiply. They are able to multiply quickly. Some factors conducive to infection include high humidity, crowding, poor air circulation, plant stress caused by over-watering, under-watering, or irregular watering, poor soil health and deficient or excess nutrients. Bacterial organisms can survive in the soil and crop debris, and in seeds and other plant parts. Weeds can act as reservoirs for bacterial diseases. Bacteria are transmitted via infected seed, propagating material and crop residues, through water splash and wind-driven rain, and on contaminated equipment and workers’ hands. Overhead irrigation favours the spread of bacterial diseases.