Postharvest foliar nitrogen (urea) is often applied to apple leaves immediately after picking for bud fertilising and/or during leaf fall for Venturia inaequalis control During 20132016 ethylene diamine tetraacetic acid copper (EDTACu to enhance leaf abscission) urea calcium nitrate and BudWiser foliar treatments were applied alone or in combination to determine their effects on leaf scar infection by Neonectria ditissima in Braeburn (201314) Scifresh and Royal Gala (201516) orchards In 201314 leaf scar infection increased sixfold when 5 urea was added to EDTACu and sprayed at the onset of leaf fall In 201516 up to a ninefold increase in leaf scar infections was observed The timing of application was more important than the amount or form of nitrogen used As a result of this research the use of ureabased foliar nitrogen fertilisers for V inaequalis before leaf fall are not recommended and growers should consider all factors affecting Neonectria ditissima infections before applying nitrogen immediately after harvest
During the 1995-96 and 1996-97 growing seasons, regular monitoring of apple leafcurling midge (ALM) (Dasineura mali Diptera: Cecidomyiidae) egg laying was conducted in three conventionallymanaged orchard properties on the Waimea Plains, Nelson. The percentage of apple shoots infested with ALM eggs fluctuated considerably between seasons. The timing of egg laying peaks was similar between orchard properties, but differed between cultivars. Peak egg laying periods occurred 7-14 days earlier on 'Royal Gala' compared with 'Braeburn'. No notable difference in the level of apple shoot tips infested with ALM eggs occurred between cultivars. Similarly, no orchard property had consistently higher or lower levels of shoot tips infested with ALM eggs during the season. The importance of these findings for monitoring ALM is discussed briefly.
Flower blight in blackcurrants caused by the fungus Botrytis cinerea has received little attention in New Zealand To determine the efficacy of a fungicide application in relation to the timing of infection fungicides were applied 5 3 and 1 day before as well as immediately after 1 2 and 5 days after an infection event Cyprodinil and fludioxonil (Switch) were chosen because of the translaminar systemic and protective mode of action Studies were conducted during the 2006 flowering season in the laboratory and in the field on commercial properties in Canterbury and Nelson Natural Botrytis flower inoculation and infection events were common during the 2006/07 production season Results suggest that timing of fungicide application is critical for B cinerea control in blackcurrants Protection of flowers was achieved with cyprodinil and fludioxonil applications from 3 days before to 3 days after an inoculation and/or infection event Reduction of flower infections resulted in increased fruit set
European canker, Neonectria ditissima, is a worldwide apple tree disease killing shoots, branches and trees, and treatment with phosphorous acid is a possible control option. The effect of six postharvest phosphorous acid (PA) treatments on fruit residues the following season was studied in Tasman on two trial sites growing ‘Scifresh’ or ‘Scilate’ apple trees. Spray treatments consisted of number (0–3) and timing (early, mid and/or late) of PA applications. Additionally, leaf-scar wounds were artificially inoculated with N. ditissima spores at the ‘Scilate’ site on 1 and 8 June 2017 to determine disease control. Symptom expression was checked regularly between October 2017 and February 2018. None of the treatments caused a statistically significant reduction in the incidence of canker development compared with the control. Two or more PA applications resulted in PA residues in fruit, at harvest, the following season. Higher PA residues were found in fruit following early applications than with late applications. More applications of PA resulted in higher residues. This finding has important implications for exporting fruit to markets that have no tolerance for PA residues.
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