Open AccessEffect of Kasugamycin, Oxytetracycline, and Streptomycin on In-orchard Population Dynamics of Erwinia amylovora on Apple Flower Stigmas
Author(s) -
Suzanne M. Slack,
Kellie J. Walters,
Cory A Outwater,
George W. Sundin
Publication year - 2021
Publication title -
plant disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.663
H-Index - 108
eISSN - 1943-7692
pISSN - 0191-2917
DOI - 10.1094/pdis-07-20-1469-re
Subject(s) - fire blight , oxytetracycline , biology , erwinia , population , orchard , streptomycin , horticulture , botany , antibiotics , microbiology and biotechnology , veterinary medicine , bacteria , medicine , genetics , demography , sociology
We assessed the effect of three antibiotics (streptomycin, oxytetracycline, and kasugamycin) on populations of the fire blight pathogen Erwinia amylovora on apple flower stigmas during three field seasons. Application timing relative to E. amylovora presence on flower stigmas had little impact on population dynamics and subsequent disease incidence. Although E. amylovora populations on water-treated flowers increased to 10 6–7 cfu flower −1 after 4 to 5 days during each experiment, the antibiotics streptomycin and kasugamycin caused statistically significant reductions in stigma populations by as many as 4 to 5 logs over a 4- to 5-day period during two of the three experiments. In contrast, the effect of oxytetracycline on E. amylovora populations on stigmas was more variable, with reductions in E. amylovora populations only observed during one of the three experiments. In agreement with the population data, the disease incidence was significantly higher for oxytetracycline-treated flowers compared with the other antibiotic treatments during 2 of 3 years. Statistical analyses of the effects of weather parameters on antibiotic activity revealed that solar radiation and temperature negatively impacted the activity of both kasugamycin and oxytetracycline. We further assessed the potential for photodegradation of formulated kasugamycin (Kasumin 2L) and found that Kasumin 2L was susceptible to degradation in vitro after exposure to a 16-h photoperiod of daily light integrals (DLIs) varying from 6 to 35 mol⋅m −2 ⋅d −1 . We further determined that exposure to three consecutive 16-h photoperiods of DLIs of 23 or 35 mol⋅m −2 ⋅d −1 reduced the available concentration of Kasumin 2L (assessed using a bioassay) from 100 μg⋅ml −1 to 10 to 20 μg⋅ml −1 . Our results correlate the superior blossom blight control efficacy of kasugamycin and streptomycin with significant population reductions in E. amylovora on apple flower stigmas but indicate that, similar to oxytetracycline, kasugamycin is vulnerable to photodegradation, which would suggest that further considerations are necessary when applying this antibiotic.