Field evaluation of treatments for the control of the bacterial apical necrosis of mango (Mangifera indica) caused by Pseudomonas syringae pv. syringae

Abstract

Bacterial apical necrosis is a critical disease in the main production area of mango in Europe. It is caused by Pseudomonas syringae pv. syringae, and produces necrotic lesions on mango buds and leaves, causing severe yield losses due to a decrease of flowering and fruit set. A field study to evaluate control treatments against bacterial apical necrosis was carried out during three seasons on mango trees cv. Tommy Atkins in Huelva (Spain). Experimental treatments included Bordeaux mixture, fosetyl-Al, acibenzolar-S-methyl, gibberelic acid, silicon gel, a mixture between acibenzolar-S-methyl and Bordeaux mixture, and combined applications of fosetyl-Al with Bordeaux mixture or silicon gel. The treatments which caused a consistent reduction in bacterial apical necrosis symptoms at similar levels to the conventional treatment with Bordeaux mixture, were the plant resistance activator acibenzolar-S-methyl and the phosphonate derivative fosetyl-Al applied singly or in combination with other compounds, which could be alternative treatments. These treatments showed a significant decrease in the necrotic buds and/or leaves numbers; however, minor differences in P. syringae-like population levels were observed. The analysis of the inhibitory and bactericidal concentrations of cupric compounds against P. syringae strains isolated from mango tissues suggests that the commercial copper-based treatments with Bordeaux mixture used in the management of mango crops do not work in a bactericidal mode of action.

Epidemiology and Control of Plant Diseases Caused by Phytopathogenic Bacteria: The Case of Olive Knot Disease Caused by Pseudomonas savastanoi pv. savastanoi

“…They were assayed to control some bacterial plant diseases like fire blight, citrus canker, apical necrosis of mango, etc. Most of these products do not produce phytotoxicity and their efficacy is sometimes comparable to that of antibiotics or copper-based compounds while others could not control these diseases (Brisset et al, 2000;Cazorla et al, 2006;Graham & Leite, 2004;Scortichini, 2002,). There are reports of acibenzolar-S-methyl-related activation of certain genes involved in defense responses in olive leaves of the cultivar Lechín de Sevilla (Muñoz et al, 2005).…”

Antibacterial activity of fosetyl‐Al, ethyl‐phosphite and phosphite against Pseudomonas syringae on plant surfaces and in vitro

“…The benefits of using phosphite (H 2 PO 3 − ), also called phosphonate, to control plant diseases caused by oomycetes have been known since the 1970s and the aluminium salt of the ethyl ester of phosphorous acid (fosetyl‐Al) has been registered as a fungicide under the trade name of Aliette (Guest & Grant, ). Fosetyl‐Al was later evaluated as a bactericide, but was found to induce variable and irregular controls of bacterial diseases (McGuire, ; Chase, ; Sugar et al ., ; Cazorla et al ., ). However, with the European Union's ban on the use of the antibiotic streptomycin in agriculture in 2004 (EUR‐Lex 32004D0129), a need for alternative methods of bacterial disease control was created, and fosetyl‐Al was registered as a bactericide in Belgium and other countries.…”

“…Accordingly, the addition of 0.938 g L −1 fosetyl‐Al to an amino‐acid‐rich agar medium reduced the pH to 3.7 and totally inhibited Pseudomonas syringae growth, although survival tests indicated that P. syringae cells were not killed at that concentration (Moragrega et al ., ); pH 3.7 is below the p K a of the R groups of histidine (6.0), glutamic acid (4.25) and aspartic acid (3.86), and below the limit of pH 4.25–4.5 tolerated by P. syringae for growth (Palleroni, ; Bultreys & Gheysen, ). Fosetyl‐Al can affect the bacterial survival (Chase, ), but 24‐h periods in shaken suspensions containing 4–8 g L −1 fosetyl‐Al were necessary to prevent P. syringae growth on agar medium 72 h after plating (Cazorla et al ., ). The indirect stimulation of plant defences by fosetyl‐Al was also proposed to play a role against bacterial diseases, as already postulated for oomycete diseases, because the acidity could not explain that neutralized fosetyl‐Al was often as efficient as fosetyl‐Al in plant trials (Chase, ).…”

Environmentally friendly treatment alternatives to Bordeaux mixture for controlling bacterial apical necrosis (BAN) of mango

“…Although many compounds have been reported to control bacterial diseases in fruit trees, only one study of control methods has been reported in mango crops. This suggested that the most effective treatment for controlling BAN was the spraying of copper compounds Bordeaux mixture (BM) (Cazorla et al. , 2006).…”

“…It forms a thick film on plant surfaces due to the calcium it contains (Becerra, 1995). BM actively controls BAN, but no effect has been observed on P. syringae levels, suggesting that antimicrobial activity may not be its main mode of action against BAN (Cazorla et al. , 2006).…”