Citrus blast—Pseudomonas syringae
Bacterial blast infections of citrus occur during cool or wet weather during the winter or spring and
usually start as black lesions in the leaf petiole and progress into the leaf axil. Once the petiole
is girdled, leaves wither, curl, and eventually drop. Entire twigs may die back. Diseased areas are covered
with a reddish brown scab. Infections result in small black spots on the fruit.
Pruning out dead or diseased twigs in spring after the rainy period reduces the spread of bacterial
blast. Scheduling fertilization and
pruning during spring or early summer prevents excessive new fall
growth, which is particularly susceptible to blast infection. Bordeaux
sprays applied before the first
rain may help prevent bacterial blast.
lesions in leaf petiole and axil