Photo 2. White spots of powdery mildew, Oidium species, on the top surface of a pumpkin leaf. The plants appeared in Photo 3.
Cucumber powdery mildew
Podosphaera xanthii and Golovinomyces cichoracearum; previously Sphaerotheca fuliginea and Erysiphe cichoracearum, respectively. These are the names of the sexual forms of the powdery mildews, but in Pacific island countries only the asexual form has been found, known as Oidium species. Unfortunately, unless the Oidium form is examined miscoscopically soon after collecting identification is difficult.
Even in 1981, the Survey of Agricultural Pests and Diseases1 recognised that samples identified as Sphaerotheca fuliginea were likely confused with Erysiphe cichoracearum. Since then other taxonomic complications have arisen from molecular analyses. Golovinomyces cichoracearum, for instance is recognised as a "species complex", i.e., it is more than one species.
In the interim, and while the taxonomy is better understood, it is best to refer to all powery mildew fungi of cucurbits from Pacific islands as Oidium species.
AUTHORS Helen Tsatsia & Grahame Jackson
1Dingley JM, Fullerton RA, Mckenzie EHC (1981) Survey of Agricultural Pests and Diseases Technical Report Volume2. South Pacific Bureau for Economic Co-operation, United National Development Programme, Food and Agricultural Organization of the United Nation. Rome, Italy. 2CABI (2017) Golovinomyces cichoracearum (powdery mildew) Crop Protection Compendium. (www.cabi.org/cpc). CABI (2016) Podosphaera xanthii (powdery multdew of cucurbits) Crop Protection Compendium. (www.cabi.org/cpc). Photo 4 (taken by Eric McKenzie), and used in this fact sheet, appeared previously in McKenzie E (2013) Golovinomyces cucurbitacearum PaDIL - (http://www.padil.gov.au).
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.
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