Abstract:
A 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 Altemaria 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.
The use of blunt syringe in inoculation studies of the-canker disease gives quick results as
compared to the spraying method.
Studies on the effect of the diseases on yield, to complete their importance were not
feasible within the period of the study.
