A etiology And Importance of Foliage Diseases Affecting Citrus in The Nursery at The Agricultural Research Station (A.R.S.). Kade.

ABSTRACT

Research work was carried out at the Agricultural Research Station to determine the disease status of the seedlings and budlings in the nursery. Field surveys were carried out on three separate occasions between October and December 2003 during the dry season and repeated in March to May 2004 in the rainy season. Four diseases were detected. These were citrus scab, citrus canker, greasy spot-like disease and brown leaf spot of rough lemon. The causal agent for brown leaf spot was confirmed to be Altem aria citri, and that for citrus canker was confirmed to be Xanthomonas campestris pv. citri, a bacterium that has not been previously reported in Ghana. Pathogens for scab and greasy spot-like disease could not be isolated and identified. Brown leaf spot and scab were found to be restricted to rough lemon, which is used as rootstock in the nursery and therefore could not be transferred to the field. Comparatively, citrus canker and greasy spot -like disease were found to have a wide host range and have infected the following citrus varieties in the nursery: late Valencia (sweet orange), waiters (grapefruit) Cleopatra mandarin, satsuma mandarin and ponkan (mandarins), king disemis and ortanique (hybrids); and the rough lemon. The two diseases have a potential of being transferred to the field as they infect the scion as well. Both the incidence and severity of the diseases in all the species and varieties of the citrus studied were higher in the rainy season than in the dry season