2014 ASHS Annual Conference

Phytophthora ramorum is a major risk to interstate trade of nursery stock. Our work focuses on chemical oxidant chemistry as a disinfectant on nursery grown Camellia japonica species. Disinfection of the plant is crucial, but the impact on plant health and phytotoxic responses are also important. Chlorophyll fluorescence was measured to determine plant stress responses to two oxidant disinfectants, mixed with and without a sarcosinate surfactant.  A parameter of fluorescence is Fv/Fm, or maximum quantum efficiency, which is the efficiency of chlorophyll to convert photons into sugars. Data were collected using a Li-Cor 6400 Leaf Chamber Fluorometer (Li-Cor, Lincoln, Neb) to evaluate the potential phytotoxicity of Camellia plans to several formulations of ClO₂ and H₂O₂ that were applied five times at three day application intervals.  Maximum quantum efficacy (Fv/Fm) increased when ClO₂ and H₂O₂ were applied with the surfactant sarcosinate to camellia foliage. Also, visual injury of the camellia foliage increased with each subsequent spray application; however, foliar injury did not exceed a marketable threshold for most treatments, until after four or five consecutive spray applications.