172 Percival and Graham: Calcium and Silicon Fertiliser and Fungicide for Pathogen Management sprayed until runoff. Treatments were applied 3 times per year at bud break (2016 March 19, 2017 March 27), 90% petal fall (2016 May 15, 2017 May 25), and early fruitlet (2016 June 3, 2017 June 6). Treatments for containerised stock and field trials are shown in Table 1. In addition, and as an industrial comparative, 6 sprays of penconazole were applied on the same dates as above, and a further 3 sprays were applied 2 weeks after early fruitlet (2016 June 21, 2017 June 25), fruit swell (2016 July 5, 2017 July 9), and (2016 July 19, 2017 July 23). Ca and Si fertilisers were applied at the manufacturers’ recommended rates. Penconazole was applied at 1 mL L-1 mended rate (full strength), and at 0.5 mL L-1 of water, manufacturer’s recom- of water, half manufacturer’s recommended rate (half strength). Leaf and Fruit Scab/Blotch Symptom Severity During each field trial, scab symptom severity of leaves and fruit was assessed commencing Septem- ber 14 each year. For containerised stock trials, leaf blotch symptom severity was assessed commencing September 24 each year. Leaf scab and blotch sever- ity for each tree was rated using a visual indexing technique and ratings on the scale: 0 = no leaf scab or blotch symptoms observed; 1 = less than 5% of leaves affected and no aesthetic impact; 2 = 5% to 20% of leaves affected with some yellowing, but little or no defoliation; 3 = 21% to 50% of leaves affected, sig- nificant defoliation and/or leaf yellowing; 4 = 51% to 80% of leaves affected, severe foliar discolouration; 5 = 81% to 100% of leaves affected with 90% to 100% defoliation. Scab severity on fruit (apple only) was calculated on the scale: 0 = no visible lesions; 1 = < 10% fruit surface infected; 2 = 10% to 25% fruit sur- face infected; 3 = > 26% to 50% fruit surface infected; 4 = > 50% fruit surface infected. The individual rat- ings for each tree in each treatment were used as a measure of scab severity for statistical analysis. Leaf scab severity ratings used in this study were based on UK and Ireland market standards for fungicide eval- uation of scab control (Butt et al. 1990; Swait and Butt 1990). Fruit scab severity was based on a scale used by Ilhan et al. (2006). Ten leaves and five fruit (apple only) per tree randomly selected throughout the crown were used for scab and leaf blotch mea- surements, with the mean calculated per tree for sta- tistical purposes. Chlorophyll Measurements A Minolta chlorophyll meter SPAD-502 was used. Chlorophyll was measured at the mid point of the leaf next to the main leaf vein. Calibration was obtained by measurement of absorbance at 663 and 645 nm in Table 1. Fungicide, calcium fertilisers, and silicon fertilisers used, concentration applied, and frequency of application. Active ingredient Penconazole* Concentration applied 1 mL L-1 Penconazole Penconazole Tetra ethyl silicate Penconazole + tetra ethyl silicate Penconazole + tetra ethyl silicate Potassium silicate Penconazole + potassium silicate Penconazole + potassium silicate Ca chloride Penconazole + Ca chloride Penconazole + Ca chloride Ca metasolate Penconazole + Ca metasolate Penconazole + Ca metasolate Water (control) 1 mL L-1 1 mL L-1 0.5 mL L-1 0.5 mL L-1 1 mL L-1 0.5 mL L-1 10 mL L-1 of water (FS) of water (FS) of water (HS) of water (FS) of water (FS) + 10 mL L-1 of water (HS) + 10 mL L-1 10 mL L-1 of water (FS) + 10 mL L-1 of water (HS) + 10 mL L-1 2.5 g L-1 of water (FS) 1 mL L-1 1 mL L-1 0.5 mL L-1 0.5 mL L-1 of water (FS) + 2.5 g L-1 of water (HS) + 2.5 g L-1 2.5 g L-1 of water (FS) + 2.5 g L-1 of water (HS) + 2.5 g L-1 of water (FS) of water (FS) of water (FS) of water (FS) of water (FS) of water (FS) of water (FS) of water (FS) of water (FS) of water (FS) 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 All treatments based on manufacturers’ recommended efficacy rates. FS = full strength, HS = half strength. Tetra ethyl silicate, potassium silicate, Ca chloride, Ca metasolate (Orion Future Technology Ltd., Henwood House, Henwood, Ashford, Kent, UK). * a protectant triazole fungicide with antisporulant activity commercially used for apple scab control (Syngenta Crop Protection UK Ltd., Whittlesford, Cambridge, UK). ©2021 International Society of Arboriculture No. of applications 6
July 2021
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