(366) Bloom Delay and Fruit Thinning of Blueberry with Soybean Oil

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  • 1 1University of Tennessee, Department of Plant Sciences, Knoxville, TN, 37796-4561
  • | 2 2N.C. State University, Horticulture Department, Raleigh, NC, 7695-7609

Trials were conducted in 2004 to compare the effects of soybean oil formulations and concentrations on flowering and fruit thinning of rabbiteye and southern highbush blueberries. Mature `Climax' bushes near Spring City, Tenn., were sprayed to runoff on 10 Feb. with water, or 9% soybean oil in the formulations TNsoy11, TNsoy12, TNsoy13, TNsoy14, or Golden Natur'l (GN). In a second trial, 3-year-old `Legacy' southern highbush plants at Spring Hill, Tenn., were sprayed on 11 Feb. with 0%, 6%, 9%, 12%, and 15% GN. A similar trial was sprayed on 5 Mar. at Fletcher, N.C., using young plants of various Southern highbush cultivars. Each formulation of soybean oil (9%) delayed bud development and flower anthesis of `Climax' bushes. Bloom opening on `Legacy' bushes was delayed by 2 to 6 days with sprays of ≥9% GN, with higher concentrations causing more delay. However, flower bud mortality of `Legacy' plants was greater when sprayed with the higher oil concentrations. `Legacy' plants sprayed with 0%, 6%, and ≥9% oil had 0%, 30% and ≥70% bud mortality, respectively, at 36 days after treatment. `Legacy' plants sprayed with 12% and 15% oil sprays had an estimated 24% and 13%, respectively, of a crop load compared to the estimated 100% crop load on control plants. Flower bud development, flower bud mortality, crop load and berry size (across cultivars) of Southern highbush cultivars at Fletcher were not affected by oil treatments. Results were variable among trials, perhaps due to factors such as cultivars, timing of application (date), maturity of plants, environmental conditions, etc. There is potential for soybean oil formulations to be used as a chemical thinner as well as to delay blooming.