Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
There have been two samples of angular leafspot that have been diagnosed this spring. One sample was from high tunnel production, the other annual strawberry under row covers. As you can see from the picture this bacterial leafspot produces angular watersoaked spots initially (Photo 1) that turn dark and eventually brown with time (Photo 2). The bacteria are limited by the vein pattern in the leaf which gives it the diagnostic angular pattern. This disease can cause leaf loss, and, when conditions are very favorable during fruit set, the calyx can become infected and that can reduce the marketability of the fruit. Wet conditions favor the disease, especially if irrigation is needed for frost protection. The bacteria that cause the spring symptoms come from systemically infected overwintered plants and dead leaves, and from infected transplants. Copper sprays can be effective in limiting spread once it is identified but over-application can be phytotoxic, so be careful. Prevention of angular leafspot in the plant nursery and its dissemination in transplants is crucial to controlling this disease.
Photo 1. Water-soaking symptoms
Photo 2. Angular leafspot symptoms.