Vol. 74 No: 2

Title:
Effect of method of application of paclobutrazol in high-density sweet cherry orchards on tree performance and apparent soil residue

Authors:
TADEUSZ JACYNA and KENNETH G. DODDS

pp: 213-218

Abstract:
Four year old 'Bing' sweet cherry trees planted at a density of ca. 1500 trees per ha were treated once with paclobutrazol (Cultar) applied as soil drench (SD) where 1 l of paclobutrazol aqueous solution was poured into a furrow around the tree trunk, or applied as a row-side drench (RSD) where 1 l of paclobutrazol solution was divided into two doses of 0.5 l and poured into two furrows located on both edges of the herbicide strip, or a bark painting application (BP) where a 20 cm wide tree bark band was brush-painted with paclobutrazol dissolved in 100% 'Surfactant WK'. A standard rate 15 mg paclobutrazol per cm² of tree trunk cross-sectional area was applied in all three cases. The SD and RSD trees showed signs of shoot growth inhibition 69 d after application, about 12 d before some inhibition was seen on the BP trees. Fruit set was reduced by both the SD and RSD but not by the BP. Yields were not influenced by paclobutrazol in the application year. The highest two-year cumulative yields were obtained from the BP, followed by the control, RSD and SD. Fruit quality (mass, diameter, firmness and soluble-solids content) was not adversely affected by the treatments. Treated trees tended to produce significantly larger fruit than the untreated control. Bio-assay with broad beans, performed 20 months after paclobutrazol application, showed that growth of the indicator plants grown in soil taken from the application treatments was reduced to 70.5, 56.1 and 23.6% of control for the BP, RSD and SD, respectively. Efficient growth control and cropping, considerable reduction of paclobutrazol residue in the soil, and thus limiting its environmental impact, makes bark application worth considering for use in sweet cherry high-density plantings.

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