Arboriculture & Urban Forestry 47(2): March 2021 Materials Tested for Efficacy Signum (a.i. 27% boscalid + 7% pyraclostrobin; BASF plc, Cheadle Hume, Cheadle, Cheshire, UK). Messenger (a.i. Harpin protein; EDEN Bioscience Corporation, N. Bothell, Washington, USA). Rigel-G (a.i. Salicylic acid [SA]; Orion Future Tech- nology Ltd, Henwood House, Henwood, Ashford, Kent, UK). Liquid Chitosan (a.i. Chitosan; Viresco [UK] Ltd, Thirsk, North Yorks, UK). Water (control). Spray Treatments Salicylic acid (SA) was used at a concentration of 3 mL/L of water, harpin protein (HP) at 0.005 g/L, and liquid chitosan (LC) at 1 mL/L, in line with manufac- turers’ labelled rates. The synthetic fungicide boscalid + pyraclostrobin was applied at 0.9 g/L (labelled rate) and at 2/3 and 1/3 labelled rate. Foliar sprays of each product were applied until runoff using a hand-sprayer (Cooper Pegler, Watling Street, Clifton upon Dun- smore, UK). Treatments, hosts, and year the experiment occurred are shown in Table 1. For consistency between years, all fungicide and IR agents were applied 4 times during a growing season at key treatment times for leaf pathogen management (Bevan and Knight 2001), Table 1. Experimental treatments, timing, and host plants. 2016 Treatment and concentration of compounds per L of water Pyrus and Aesculus Salicylic acid (3 mL) Harpin protein (5 mg) Boscalid + pyraclostrobin (0.9 g) Boscalid + pyraclostrobin (0.9 g) + Harpin protein (5 mg) Boscalid + pyraclostrobin (0.6 g) + Harpin protein (5 mg) Boscalid + pyraclostrobin (0.3 g) + Harpin protein (5 mg) Boscalid + pyraclostrobin (0.9 g) + Salicylic acid (3 mL) Boscalid + pyraclostrobin (0.6 g) + Salicylic acid (3 mL) Boscalid + pyraclostrobin (0.3 g) + Salicylic acid (3 mL) Liquid chitosan (1 mL) Boscalid + pyraclostrobin (0.9 g) + Liquid chitosan (1 mL) Boscalid + pyraclostrobin (0.6 g) + Liquid chitosan (1 mL) Boscalid + pyraclostrobin (0.3 g) + Liquid chitosan (1 mL) Water control X Year and host 2017 Pyrus and Aesculus X X X X X X X X X X X X X X X 2018 Pyrus X 87 namely, bud break (mid-March), flower opening/green cluster (late-April), 90% petal fall (mid-late May), and early fruitlet (mid-late June). Prior to spray treat- ments, plants were inspected to ensure no visible symptoms of leaf infection were apparent. During spray treatments, polythene screens 2.5-m high were erected around each tree to prevent dispersal of sprays and possible cross contact. The base of the tree was covered with a 0.5 m × 0.5 m polythene mulch to pre- vent any soil percolation. Insect Pest Management A minimal insecticide program to prevent pest infes- tation was performed based on the pyrethroid insecti- cide deltamethrin (product name Bandu; Headland Agrochemicals Ltd, Saffron Walden, Essex, UK) which was applied every 6 weeks during each growing season. Trees were sprayed until runoff. Treatment Efficacy The degree of protection conferred by each treatment was assessed by recording 3 parameters towards the end of the growing season (25–30 September). Leaf/Fruit Pathogen Symptom Severity Severity of symptoms caused by V. pirini and Guignar- dia aesculi on leaves was assessed with a visual index X ©2021 International Society of Arboriculture
March 2021
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