174 Percival and Graham: Calcium and Silicon Fertiliser and Fungicide for Pathogen Management Field Trials: V. inaequalis Irrespective of Ca, Si, and penconazole combination, and whether applied at full or half strength, no leaf phytotoxic effects were recorded (data not shown). Damaging outbreaks of leaf and fruit scab symptoms were recorded on control trees, where visual index values of 4.7 and 4.2 (leaves) and 2.6 and 2.8 (fruit) were recorded at the end of the 2016 and 2017 grow- ing seasons, respectively (Tables 2 and 5). The great- est reductions in leaf and fruit scab symptom severity were recorded following 6 applications of the syn- thetic fungicide penconazole at full strength, where no leaf scab was recorded in 2016 and no fruit scab in 2016 and 2017 (Tables 2 and 5). This treatment also had the greatest effect on fruit yield (Table 5), leaf chlorophyll content (Table 3; 2016 growing season only), and crown volume (Table 4) compared to all other treatments. Limited efficacy was recorded when penconazole at half strength (0.5 mL L-1 ), Ca metasolate, or potassium silicate alone was applied 3 times during the growing season. Leaf and fruit scab severity symptoms, fruit yield, and leaf chlorophyll content were, in most cases, not significantly differ- ent from water-treated controls (Tables 2, 3, and 5). However, penconazole at half strength (0.5 mL L-1 ), Ca metasolate, or potassium silicate alone did signifi- cantly increase crown volume compared to water- treated controls (Table 4). Penconazole at half strength (0.5 mL L-1 ) in combination with either Ca metasolate or potassium silicate, when applied 3 times during a growing season, in most instances, signifi- cantly reduced leaf and fruit scab severity symptoms (Tables 2 and 5) and significantly increased fruit yield (Table 5), leaf chlorophyll content (Table 3), and crown volume (Table 4) compared to water-treated controls. These effects were additive based on Lim- pel’s formula. Three spray applications of penconazole at full strength (1.0 mL L-1 ), tetra ethyl silicate, or Ca Table 2. The influence of calcium and silicon fertilisers and synthetic fungicide combinations applied as foliar sprays on the severity of Guignardia leaf blotch (Guignardia aesculi) on Aesculus hippocastanum (container-grown stock) and apple scab (Venturia inaequalis) on Malus domestica cv. 'Golden Delicious' (field trials). A. hippocastanum Treatment Water (control) Penconazole (1 mL × 6 sprays) Penconazole (1 mL) Penconazole (0.5 mL) Tetra ethyl silicate (10 mL) Penconazole (1 mL) + tetra ethyl silicate (10 mL) Penconazole (0.5 mL) + tetra ethyl silicate (10 mL) Potassium silicate (10 mL) Penconazole (1 mL) + potassium silicate (10 mL) Penconazole (0.5 mL) + potassium silicate (10 mL) Ca chloride (2.5 g) Penconazole (1 mL) + Ca chloride (2.5 g) Penconazole (0.5 mL) + Ca chloride (2.5 g) Ca metasolate (2.5 g) Penconazole (1 mL) + Ca metasolate (2.5 g) Penconazole (0.5 mL) + Ca metasolate (2.5 g) Treatment = synergistic effect according to Limpel’s formula. Add were greater than the effect of each product alone. All values mean of 6 trees, 10 leaves per tree. Leaf scab and blotch severity 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, significant 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. ©2021 International Society of Arboriculture Leaf blotch symptom severity index 2016 3.5d 2017 3.2g 0.0a 2.0c 3.1d 1.8c 0.9b (Syn 1.6bc (Add 3.0d 1.3bc (Add 2.8d (Add 1.7c 0.8b (Syn 1.5bc (Add 3.1d 1.6c (Add 2.8d (Add < 0.001 ) ) ) ) ) ) ) ) 0.0a 1.8cd 3.0fg 2.0de 1.3bc (Add 1.7cd (Add 2.7fg ) ) 1.5bcd (Add 2.5ef (Add 1.8cd ) 1.0b (Syn ) 1.9cde (Add 2.9fg < 0.001 Lower case letters indicate significant differences between means for each evaluation date by LSD (P = 0.05). Syn = additive effect if values did not exceed Limpel’s formula but 1.6bcd (Add 2.5ef (Add ) ) ) ) M. domestica cv. 'Golden Delicious' Leaf scab symptom severity index 2016 4.7j 0.0a 2.2de 4.2ij 2.8efgh 1.0bc (Syn 2.6efg (Add 3.6hi ) ) 1.5bcd (Add 3.4ghi (Add 2.4def 0.8ab (Syn 1.6bcd (Syn 3.3fghi < 0.001 ) ) 1.9cde (Add 3.5ghi (Add ) ) ) ) 2017 4.2h 0.5a 2.1def 3.7gh 2.9fg 1.2abc (Syn 2.6ef (Add 3.8h ) ) 1.8bcde (Add 3.6gh (Add 2.4ef ) 1.0ab (Syn 2.0cde (Add 3.7gh < 0.001 ) 1.4bcd (Add 3.7gh (Add ) ) ) )
July 2021
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