Citrus Bacterial Canker Pustules Are Associated With Leafminer Galleries IN IRAN

Abstract

Citrus bacterial canker is one of the most destructive diseases of citrus in southern Iran. During 2000-2001 and 2005-2006, this disease became endemic showing a reduced severity. This was mainly due to the unfavorable climatic conditions, i.e. low rainfall during the previous years in particular. Control measures included pruning of symptomatic shoots and the use of copper sprays. In Rudan (Hormuzgan province), citrus pustules are usually observed on the lower leaf surface alongside the galleries caused by Phyllocnistis citrella. Bacteria were isolated from these pustules and identified as Xanthomonas citri pv. citri A (Xac) based on biochemical and physiological characteristics (Gram and oxidase reactions, nitrate reduction, urease, hydrolysis of aesculin, casein, gelatin, starch, Tween, sodium chloride tolerance, litmus milk, H2S generation from cysteine and phosphatase, xanthomonadin production, carbohydrate utilization); differential phenotypic features such as bacterial mass colour on Ayer medium containing L-proline, utilization of glycogen, maltose, dextrin, starch (Mohammadi et al., 2001); broad pathogenicity range on inoculated hosts including Mexican lime, unshu tangerine, sour orange, grapefruit and sweet orange. Larval leafminer damage results in elevated incidence and severity of citrus bacterial canker disease (Belasque et al., 2005). Since Ph. citrella is potentially capable of disseminating Xac, thus facilitating canker infection, it is suggested that controlling this pest may result in preventing Xac outbreaks in citrus groves. The association of bacterial canker pustules with leafminer tunnels has previously been reported from North Yemen and India (Cook, 1988; Belasque et al., 2005) but not in Iran, this constituting the first record.