Valdensinia leaf spot (Valdensinia heterodoxa)

Valdensinia leaf spot: biology

Valdensinia leaf spot (Valdensinia heterodoxa) is a leaf disease that’s a growing concern in blueberry fields.

In early to mid-June, spores are produced from the fungus that overwinters in infected leaves on the ground. A wet period of weather stimulates spore production. Spores infect leaves and cause sizeable spots or lesions (5 to 10 mm in diameter) followed by leaf drop within a couple of days. Defoliated sprouts initiate new vegetative growth that reduces fruit bud production. If wet weather continues during the spring, several spore infections can take place; infection on the dropped leaves can continue to produce spores. The fungus can survive in infected leaves for at least two years.

The Valdensinia fungus is unique because it produces an extremely large spore that is visible without magnification. It is easily distinguished from other leaf diseases by the large size of the leaf spot, which is brown and circular with a red margin. These spores and infected leaves cling to footwear and machinery, which is the primary way that the disease spreads from field to field.

Valdensinia infection can result in lower crop yields, smaller berries and a decreased number of flowers. Plant health is also affected by leaf drop.