Bacillus subtilis QST 713, copper hydroxide, and their tank mixes for control of bacterial citrus canker in Saudi Arabia

Citrus Bacterial Canker (CBC) is a serious disease that affects production of almost all commercial citrus cultivars in subtropical citrus growing regions worldwide. In this study, the effectiveness of monthly foliar sprays of wettable powder formulation Serenade MAX of Bacillus subtilis QST 713, alone or as tank mixes with copper hydroxide on CBC disease development was evaluated under greenhouse and uncovered nursery conditions. The QST 713 as a tank mix with copper hydroxide reduced significantly the disease severity and incidence, followed by the copper hydroxide treatment, compared to the control. The disease incidence on leaves of inoculated trees treated with a combination of copper with QST 713 was never higher than 19%, whereas, the disease incidence reached 43% for non-sprayed trees. It was possible to reduce the number of copper sprays up to 6 sprays per season when it was mixed with the bio-fungicide QST 713 to effectively control CBC compared with 8 sprays of copper hydroxide alone per season. Based on our results, the application of QST 713 not only may have potential for CBC management in conjunction with copper hydroxide or other disease control but also may reduce the frequency or rate of copper sprays in citrus groves