Helminthosporium Leaf Spot -- Bipolaris spp.
Host:palms, ficus, assorted foliage
Symptoms: This disease causes reddish-brown to black spots, approximately 2- to 5-mm long, all over the leaf surface. Yellow margins typically appear around the spots on palms. These spots coalesce under optimum conditions, forming irregularly shaped necrotic areas on leaf tips and along the margins.
Conditions Favoring Disease: This disease is favored by overhead irrigation and exposure to rainfall. Plants exposed to full sun are more severely affected by this disease than those produced with partial shade.
How Pathogen Survives/Disperses: Healthy plants can be easily infected by placing diseased plants in the same greenhouse or area. Splashing water, commonly produced by overhead irrigation, can easily dislodge large numbers of conidia and disperse them onto healthy tissue. Conidia can also be distributed by wind-driven rain.
Photo and write up provided by Syngenta Professional Products