Numerous cracks occur in the cuticle covering leafminer galleries providing means for bacteria to penetrate directly into the palisade parenchyma and spongy mesophyll which are highly susceptible to infection. Citrus foliar wounds normally callus within 1-2 days, however, the extensive wounds composed of the entire leafminer feeding galleries do not callus for 10-12 days, greatly extending the period of susceptibility of galleries to infection. Isolates were discovered in Oman, Saudi Arabia, Iran, and India that produce Canker A-like lesions only on Mexican lime (termed A* strains), and appear to be distinct serologically from all other known forms. Another atypical form of Canker A bacterium has been described from Reunion and surrounding islands in the Indian Ocean which has high levels of resistance to a number of antibiotics.
The maximum and optimum temperature ranges for growth are to 39°C (95 to 102°F) and 28 to 30°C (82 to 86°F), respectively.
Leafminer infestations can be very prevalent and severe producing hundreds if not thousands of potential infection courts on individual trees.
When bacterial dispersal events occur in the presence of the leafminer, not only is inoculum production greatly exacerbated, but so is the potential for infection over the entire dispersal range.
Pathogen Confirmation: Serology, bacteriophage typing, fatty acid profiles, PCR (polymerase chain reaction), and DNA analysis are useful for identification and classification of bacterial isolates into pathovars.
However, when such techniques are unavailable, strains of X. citri can be distinguished from other pathovars by a panel of susceptible and resistant citrus hosts.