Effect of temperature on growth of Penicillium digitatum and Geotricum candidum on agar and on citrus furit and chemical control of Post-harvest Rot caused by the two fungi.

Abstract PeniciIIum digitatum and Geotrichum candidum were isolated from infected citrus fruits collected from cold storages of Riyadh, Saudi Arabia. Growth rates of the fungus at 5, 10,20,25,30 and 35C were compared on agar and on fruit. The rate increased with increased temperature, reaching optima at 20 and 25C, respectively, on agar and on fruits for P. digitatum and 30C for G. candidum on both agar and fruit. The growth rate of both fungi dropped sharply at 35C on agar but less on fruit. To control the fruit rot of citrus caused by P. digitatum and G. candidum, bavistin, benomyl, guazatine and imazalil were used at the rate of 500 mglliter. Fruits were inoculated with the respective fungi and after 20 hours of incubation dipped for one minute in the fungicidal solutions separately. The infected fruits were incubated in polythene bags at room temperature for two weeks. All the tested fungicides reduced the fruit infeciton caused either by P. digitatum or by G. candidum. Gauzatine was more effective than the other fungicides and it totally inhibited the rot caused by either of the two fungi. Key Words: Citrus fruit rot; P. digitatum; G. candidum; Temperature; Fungicides