The relationship of the citrus canker bacterium Xanthomonas axonopodis pv citri with the citrus leafminer (CLM), Phyllocnistis citrella Stainton was investigated. The experiment was conducted under laboratory conditions at 28±2ºC, 70±10% RH and 14h photophase and in a greenhouse. Sweet orange (Citrus sinensis L. Osbeck) "Caipira"cv was used to rear CLM. Plants inoculated with 2nd and 3rd instar larvae or pupae showed high percentages (94.3, 98.3 and 100%, respectively) of bacterium-infected leaves. The damage caused by this insect was responsible for the increase in citrus canker infestation. The leaf infection rate by X. axonopodis pv citri on pre-injured leaves was similar to that observed on mechanically damaged leaves inoculated with the bacterium, with 94.1% to 97.0% of the leaves presenting bacterial pustules. The bacterium can also penetrate through the stomata. An 11-fold lower infection rate was observed as compared to the leaves injured by the insect seven days after inoculation. Under such conditions the percentage of cankered leaves increased to 41.2% at 14 days, a value corresponding to about 50% of the leaves attacked by the insect. In this paper it is also pointed out the significance of the damages caused by CLM in terms of the increase of citrus canker, since the favorable microclimatic conditions of temperature and relative humidity inside the mines built by the larvae account for an improved development of the bacterium.
Insecta; pest; disease; citrus; leafminer; vector
