Effectiveness of Kasugamycin Against Erwinia amylovora and its Potential Use for Managing Fire Blight of Pear

Abstract

Comparative field studies on the management of fire blight were conducted in California on Asian and Bartlett pear using single-bactericide, mixture, and rotation treatments of selected compounds. Treatment efficacy was evaluated based on the natural occurrence of the disease or after inoculation with Erwinia amylovora. Kasugamycin at 100 mg/liter demonstrated similar or higher pre- and post-infection activity than the industry standards, streptomycin and oxytetracycline. Phytotoxicity caused by kasugamycin was observed only when five or six sequential weekly applications were done. In a six-spray rotation program including three bactericides (copper, kasugamycin, and oxytetracycline), with each being used twice, phytotoxicity was minor. Baseline sensitivity concentrations for kasugamycin were established for growth of 376 isolates of E. amylovora from California. Values for the lowest concentration where a reduction in growth on nutrient agar was observed ranged from 3.5 to 18.3 mg/liter, with a mean value of 8.7 mg/liter. Values for ≥95% inhibition of growth ranged from 6.9 to 46.7 mg/liter, with a mean value of 18.5 mg/liter. These inhibitory values for kasugamycin were higher than those for streptomycin or oxytetracycline. The in vitro activity of all three compounds was highly dependent on the agar medium used in the sensitivity assay. The activity of kasugamycin was also highly dependent on the pH of the medium and was significantly higher at pH 5.1 than pH 7.3. With the planned registration in the United States, kasugamycin represents the first new, highly effective bactericide for managing fire blight in over 40 years.

Two types of genetic carrier, the IncP genomic island and the novel IncP‐1β plasmid, for the aac(2′)‐IIa gene that confers kasugamycin resistance in Acidovorax avenae ssp. avenae

“…There seems to be no correlation between insertion of the streptomycin‐resistant transposon into pAAA83 and streptomycin usage. However, KSM has been rated as a highly effective drug against streptomycin‐resistant E. amylovora in the USA (Adaskaveg et al ., ; Jurgens and Babadoost, ; McGhee and Sundin, ). Monitoring the susceptibility of KSM to other phytopathogenic bacteria is important for the sustainable use of antibiotics.…”

“…Many bacterial diseases caused by members of the genera Pseudomonas and Erwinia are also controlled by KSM in various countries (Hiramatsu et al ., ). Recently, KSM has been demonstrated to be an effective bactericide against fire blight caused by Erwinia amylovora in the USA, one of the most destructive diseases of pome fruit trees, especially apple and pear (Adaskaveg et al ., ; Jurgens and Babadoost, ; McGhee and Sundin, ).…”

Scientific Opinion on the pest categorisation of Erwinia amylovora (Burr.) Winsl. et al.

“…There are a limited number of products available, generally with moderate efficacy, such as copper compounds and certain antibiotics that are applied preventatively (Johnson and Stockwell, 1998;Adaskaveg et al, 2011;Ngugi et al, 2011). Conventional antibiotics, such as streptomycin, tetracycline or kasugamicin, that are authorised for use against fire blight in several countries (e.g.…”

Evaluation of management of bacterial stalk rot of maize (Dickeya zeae) using some chemicals and bio-agents

“…Bleaching powder and combination of antibiotics with cupper fungicides found effective to checks the development of Erwinia spp. (Lal et al, 1970;Thind and Payak, 1972;Adaskaveg et al 2011 ). Realizing the importance of this disease, the present studies were initiated to isolate, identify and characterize the pathogen with respect to its aggressiveness and also to evaluate different antibacterials and bioagent under in vitro and in vivo condition against this pathogen.…”