Association of Citrus Canker Pustules with Leaf Miner Tunnels in North Yemen. A. A. Cook, Horticulture Improvement and Training Subproject, California State Polytechnic University and USAID, Sana’a, Yemen. . Plant Dis. 72:546. Accepted for publication 4 December 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0546D.
Bacterial canker, Asiatic form, was introduced into Yemen with a shipment of citrus plants from India. Some infected trees were distributed before the disease was detected, and an experimental farm used as a nursery for production of budded citrus seedlings eventually became contaminated. Inspection of varieties there before their destruction, and subsequently of several other plantings, revealed many leaf infections associated with tunnels made by larvae of the leaf miner Phyllocnistis citrella Staint. Pustules often developed en masse over and along the entire length of tunnels but on one leaf surface only (more often the lower). The leaf miners showed no obvious preference for specific citrus varieties, and many varieties in addition to the popular and susceptible Mexican lime were infected. The seasonal rainfall, often with high winds, blowing sand, and temperatures conducive to canker infection, can account for some spread of the disease, but the extended host range and the fact that pustules often were found nowhere else on the leaf except in association with tunnels suggest that leaf miners can disseminate and facilitate infection by the canker bacterium.