Non-pesticide control of citrus bacterial canker
Date Issued
2009
Date
2009
Author(s)
Chen, Yu-Chien
Abstract
Citrus bacterial canker (CBC), caused by Xanthomonas axonopodis pv. citri (Xac), is the most important and destructive disease in the international citrus industry. In Taiwan, the earliest report of citrus bacterial canker is in 1932, and it became the most important disease in local citrus industry in 1952. CBC occurs on the leaves, stems, and fruit. The lesions on leaves become raised and corky, surrounded by a chlorotic halo, and the centers of the lesions become gray and crater-like. Defoliation and twig dieback become a problem as the disease progresses on a plant. In 1995, Vauterin et al. reclassifies pathovars of Xanthomonas campestris as X. axonopodis pv. citri (original X. campestris pv. citri pathotype A), X. axonopodis pv. aurantifolii (original X. campestris pv. citri pathotype B, C, and D), and X. axonopodis pv. citrumelo (original X. campestris pv. citri pathotype E). Our field survey in Taiwan showed that 90% of Xanthomonas campestris are X. axonopodis pv. citri. Spraying with copper pesticides is a traditional disease control method against CBC, such as 4-4 Bordeaux mixtures, 56% cuprous oxide WP, and 81.3% Kasuran WP. However, copper pesticides can induce phytotoxicity at higher temperature, increase mite population in citrus orchard and cause environmental pollution if over-used. It may produce the anti-copper strains of Xac. For these reasons, the purpose of this study is to develop non-pesticide control methods for CBC by using bicarbonates, salicylic acid, caffeine, Bacillus subtilis, fermentation products of Streptomyces candidus, narrow-range oil, and garlic extract. The action mechanisms for these non-pesticide material are killing, systemic acquired resistance, biological control, and physical protection. Results of pot experiments in the greenhouse showed that caffeine and garlic extract were effective in suppressing CBC on orange, fermentation products of Streptomyces candidus and salicylic acid on ponkan, and salicylic acid and fermentation products of Streptomyces candidus on Madou peiyu. Results of field experiments, conducted on NTU farm, showed that salicylic acid and fermentation products of Streptomyces candidus were effective in suppressing CBC on orange, fermentation products of Streptomyces candidus and garlic extract on Madou pomelo and lemon. It is worth to note that narrow-range oil increased CBC in both pot and field experiments.
Subjects
citrus bacterial canker
non-pesticide control
salicylic acid
fermentation products of Streptomyces candidus
garlic extract
SDGs
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