- Worldwide distribution. On watermelon (and squash), and other members of the cucumber family, including weeds. A minor disease, worse under shade.
- Small, about 5 mm, round spots with grey centres, brown margins, and sometimes yellow halos. Centres may fall out, spots merge, resulting in black areas, and leaf fall.
- Spores on the underside of the leaves are spread in wind and rain.
- Cultural control: do not plant new crops next to old; use 3-4-year rotation; weed; do not grow watermelon under shade; collect and burn trash after harvest. Chemical control: copper, chlorothalonil, or mancozeb.
Pacific Pests, Pathogens, Weeds & Pesticides
Cucurbit leaf spot (145)
Photo 1. Symptoms of cucurbit leaf spot, Cercospora citrullina, on squash, showing many small spots with grey centres.
Cercospora leaf spot
Cercospora citrullina: note, previously this has been a name for Dydymella bryonae (now Stagonosporopsis cucurbitacearum) (see Fact sheet nos. 07 & 201)
AUTHOR Grahame Jackson
Information from Gerlach WWP (1988) Plant diseases of Western Samoa. Samoan German Crop Protection Project, Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) Gmbh, Germany; and Schwartz, Gent DF (2007) Cercospora leaf spot (cucumber, melon, pumpkin, squash, and zucchini). High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State University and Montana State University. (http://wiki.bugwood.org/uploads/CercosporaLeafSpot-Cucurbits.pdf); and Cucurbit diseases (undated) Cercospora leaf spot. UF/IFAS. University of Florida. (https://plantpath.ifas.ufl.edu/u-scout/cucurbit/cercospora-leaf-spot.html). Photos 1&2 Gerald Holmes, Valent USA Corporation, Bugwood.org.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.