New Zealand pipfruit crops require postharvest fungicides for control of European canker, caused by Neonectria ditissima. Fungicide efficacy trials to protect leaf scars from N. ditissima infections were conducted during autumn 2013 and 2014. Disease control of artificially inoculated leaf scars was achieved by single applications of copper oxychloride and copper oxide, but not copper hydroxide, applied at 4.3, 1.1 and 0.6 kg elemental copper/ ha respectively. Control of leaf scar infections by copper oxide (0.65 and 0.95 kg elemental copper/ha) was similar to control by captan. Leaf scars (0-10 days old) remained susceptible to infections up to 10 days after leaf fall; disease control was achieved by re-distribution of copper and captan fungicides onto new leaf scars. Disease control using copper oxide was consistent and similar to control using captan. The copper product, and concentration of elemental copper, are important for successful control of leaf scar infections by N. ditissima.
Carbendazim can be used by New Zealand pipfruit growers for control of European canker caused by Neonectria ditissima A total of 162 N ditissima isolates were tested for carbendazim sensitivity using a mycelial growth assay on amended malt extract agar plates at concentrations from 02 mg/litre Generally isolates ceased growth at 2 mg/ litre carbendazim with 65 isolates ceasing growth at 1 mg/litre The EC50 values calculated for 19 isolates ranged from 051 to 138 mg/litre The data suggested that isolates ranged from sensitive (EC50100 mg/litre The isolates tested were mostly sensitive to carbendazim but some showed a shift towards intermediate resistance Mycelial growth tests at 2 mg/litre may be a useful tool to screen single spore isolates quickly for potential carbendazim resistance
The fungus Neonectria ditissima can cause European canker in apple nursery trees In this study ten treatments of EMLA 9 rootstocks budded with Royal Gala were examined 5 Treatments included combinations of five budding tapes two budding methods and three fungicidal treatments Fifteen months after inoculation all Tbudded trees had died Chipbudded trees inoculated after tying with either Flexiband type C or plastic precut strips displayed significantly more canker (21 and 22 respectively) than those tied with Buddy tape (11 P
Neonectria ditissima is the causal organism of European canker in apple Conidia are formed in sporodochia in canker lesions and released during rain The splash pattern of conidia was monitored in four directions from a central inoculum source held at approximately 17 m height using vertical and horizontal rain traps trap plants and petroleumjellycoated glass slides during simulated rain events Nonlinear models were fitted to the conidia count data to estimate the proportion of inoculum exceeding any distance from the inoculum source When fitted to horizontal rain trap data the model suggested that half of all spores splashed beyond 042 m from the inoculum source and 4 travelled over 2 m Conidia were observed at a greater distance from the inoculum source using rain traps than glass slides In a separate set of experiments water was dropped in single droplets from various heights onto either a sealed surface or bare soil and watersensitive paper was used to estimate droplet sizes and dispersal (height and distance) Water droplets were found to splash up to 120 cm outwards and 60 cm upwards Smaller droplets travelled further than larger droplets
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