Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
This week I received the pumpkin fruit shown below. The fruit has bacterial leaf spot, which is a disease that causes lesions on both leaves and the fruit. The disease is often seed borne and can be spread from plant to plant in the field by irrigation or splashing rain. It is favored by warm wet weather. Leaf symptoms are small, less than ¼ inch, angular, water soaked lesions. These lesions often occur near a vein and may not be very noticeable. Fruit lesions are initially very small, sunken tan spots like those in the image. These spots often have a small dark border. When they enlarge they can crack and the lesions will penetrate the fruit. Control measures are sanitation, bacterial seed treatment, avoidance of overhead irrigation, and crop rotation. Copper sprays may be effective if applied early in the season to reduce plant to plant spread, however once the lesions are present on the fruit, it is too late.
