Disease: Calonectria leaf spot (Cylindrocladium leaf spot)

Pathogen: Calonectria thea, C. colhounii, C. ilicicola

Hosts: In Hawaii, Howea forsteriana (without wounding), Chamaedorea elegans, Dypsis lutescens, Laccospadix australasica; other hosts worldwide

Symptoms: Leaf spots generally grayish brown, dark brown or nearly black; lesions often gray in center and may have a brownish black edge; young leaf spots are brown, circular (0.5 mm diameter) and sometimes surrounded by a chlorotic zone about 1 mm wide; old leaf spots are circular to elliptical, up to 3 x 5 mm; rachis and petioles may be infected; as disease develops, lesions coalesce with large bands of necrotic leaf tissue appearing

Signs: Whitish masses of fungal spores and mycelium can form on older lesions

IPM: Irrigation management and moisture control (keep leaves dry; irrigation timing and application method; reduce overhead irrigation; use solid-cover greenhouses); increased plant spacing; reduce relative humidity; sanitation practices to reduce inoculum (examine crop every few days); segregate severely diseased plants; minimize all plant wounding and plant stressors

Fungicides*: Clearys 3336 (Thiophanate methyl), mancozeb (Dithane), Chipco, Medallion

Back to the Palm Pest and Disease Image Gallery

*Registered for use in Hawaii.

*Named products are not necessarily recommended by the University of Hawaii.

*Always follow the pesticide label instructions.