Fig tree leaves have the shape of an open palm and three to seven lobes with serrated edges. This foliage is thick, with a coarse surface and a softer hairy underside. It reaches 10 inches long and wide. Fig leaves are susceptible to fungal and viral diseases that cause early leaf drop and compromise the fig crop.
The fungus Cerotelium fici causes leaf rust usually in mid to late summer. Reddish-brown spots appear on the infected leaves’ underside and yellow powdery spores cover these spots. As the disease progresses, the affected foliage becomes yellow and brown before dying and dropping to the ground. Since fruiting depends on healthy leaf function, leaf rust also interferes with your fig crop by reducing its yield. No fungicide is approved to treat leaf rust on fig trees.
Fig mosaic is a viral disease transmitted by the mite Aceria fici. It appears as yellow spots on the foliage or as completely yellow leaves. As the disease develops, rust-colored borders surround the yellow spots. (See References 4) According to Purdue University, diseased fig trees should be eliminated, as there’s no cure for fig mosaic.
Aerial or Web Blight
Leaves with aerial or web blight become yellow or brown as well as water soaked. The blight progresses, turning the foliage’s surface white. Brown webs made of fungal spores also appear on its underside. Even though the leaves die, they often remain on the tree, held by fungal webbing.
Two funguses cause leaf spot on fig leaves, says Purdue University: Cylindrocladium scoparium and Cercospora fici. The highest incidence of this disease occurs in the rainy season. It begins with reddish spots on the foliage. Their centers change to a tan color as they grow in size. Fig leaf spots have brown borders encircled by yellow rings. Lesions also appear on the foliage’s edges. Severe infection causes early leaf drop.
Humidity and warmth are the ideal conditions for the anthracnose fungus to spread. It infects leaves, causing brown and black spots encircled by yellow borders. The size of these blemishes increases with disease progression, and severe cases of anthracnose lead to premature leaf drop.