Olive oil application during an approximate 10-day period following the time at which all drupelets within ‘Mission’ fig fruits had turned red was effective in stimulating fruit growth and maturity. Olive oil was found to yield ethylene, particularly when exposed to solar irradiation, and it is this degradation product that undoubtedly is the stimulative agent.
Naphthenic oil with and without succinic acid-2,2-dimethylhydrazide (SADH) was applied to dormant tung trees in February or early March to delay bloom in the spring. A late frost occurred in March 1968; the only branches of the trees to flower and set fruit were those that were treated with napthenic oil and oil with SADH. By contrast, branches treated with aqueous SADH were not saved. In 1969, branch sprays of 10% oil with 1% SADH resulted in delaying bloom up to 5 days and in setting more fruit than the control. In 1970, sprays of 50% oil with 2% SADH delayed bloom on 5-year-old tung trees by approx 2 weeks.
Treatments of dormant oil, at rates of 0, 3, 6, 9, or 12 % (v/v), were sprayed until drip on four year old `Biscoe' peach trees on February 6, 1990. Another treatment was applied as a split application with 6 % applied on the previous application date and a second application of 6% solution applied on February 12. The internal atmosphere of bud and twig was modified by the oil treatment. The internal concentration of CO2 was elevated the morning following treatment and continued higher than the control for seven days. A second application Of 6% oil resulted in additional elevation of internal CO2. External evolution of CO2 of all oil treated twigs was 6 to 18% lower than the control 8 days after treatment. Bud phenology and bloom date of trees receiving higher rates of oil were slightly delayed.
Phytotoxicity of horticultural oil, applied shortly before antifungal sulfur, was evaluated for 23 grape cultivars. Oil application significantly reduced accumulation of soluble solids in berries of 9 of 23 cultivars, but there was no relationship with visible foliar injury. Treatment of leaves of Vitis labrusca `Catawba' with 1.5% JMS Stylet-Oil reduced leaf net photosynthesis (Pn) by 50% to 60% and of Vitis vinifera `Chardonnay' by 20% to 30% 1 day after application. Pn was reduced only when the lower (abaxial) leaf surface was treated; treatment of only the adaxial leaf surface had little effect. The Pn depression in `Catawba' persisted 3 to 4 weeks, whereas reductions in `Chardonnay' persisted less than 2 weeks. The Pn-depressing effect of oil was not significantly ameliorated by real or simulated rainfall, and washing the lower leaf surfaces with water and detergent also had only limited effect. There was no significant difference in Pn depression from oil applications made in the middle of the day (stomata open) compared to application in the evening (stomata closed), or from oil applied at higher versus lower application pressure. The greater sensitivity of `Catawba' than `Chardonnay' to Pn depression by oil may be related to the amount of oil retained by the leaves; the pubescent lower leaf surfaces of `Catawba' retained more than twice as much spray emulsion as did the more glabrous leaves of `Chardonnay'. Visible injury was mild in both cultivars, with small water-soaked lesions developing more commonly on `Chardonnay' than on `Catawba' leaves. Spray oil retention data for additional cultivars suggested that differences in retention can explain a portion of the differences in horticultural oil phytotoxicity.
The objective of this study was to examine efficacy of soybean oil dormant sprays to manage San Jose scale (Quadraspidiotus perniciosus Comstock) on apple (Malus ×domestica Borkh.). On 14 Feb. 1994 and again on 20 Feb. 1995, `Bounty' apple trees were: 1) left unsprayed (control) or sprayed to runoff with: 2) 3% (v/v) or 3) 6% degummed soybean oil with 0.6% (v/v) Latron B-1956 sticker spreader, or 4) 3% 6E Volck Supreme Spray petroleum oil. Crawler emergence occurred 17 May-28 June, 7 July-30 Aug., and 7 Sept.-24 Oct. 1994. First-generation crawler emergence had started by 8 May in 1995. Both 3% petroleum oil and 6% soybean oil sprays reduced the numbers of first- and second-generation crawlers by 93% in 1994 and first-generation crawlers by 98% in 1995. The 3% soybean oil treatment reduced first- and second-generation crawlers by 60% in 1994 and first-generation crawlers by 83% in 1995. In 1995, apple fruit infestations by first-generation scales on the 3% soybean-, 6% soybean-, and 3% petroleum oil-treated trees did not differ significantly, but all fruit were significantly less infested than the controls.
`Redhaven' peach trees at the Knoxville Experiment Station were sprayed to runoff on 3 February 1993 with single applications of 0, 2.5, 5.0, 10.0, or 15.0% (v/v) degummed soybean oil with 0.6% Latron AG 44M emulsifier. Treatments were arranged in a randomized complete block design with 6 single tree replications. The internal CO2 concentration of treated twigs was elevated the first day and continued to be significantly higher than the control through the fifth day following treatment. Respiration rates of soybean oil treated buds-twigs were lower than the control for the first eight days after treatment. Flower bud and bloom development were delayed by treatment of trees with 5.0 to 15.0% soybean oil. Treatment with 5.0% oil delayed bloom approximately 4 days. The greatest delay (approximately 6 days) occurred after treatment with 10.0 or 15.0% oil. Yield was reduced and fruit size increased as the concentration of soybean oil was increased. Optimum fruit size was achieved with the 5.0% soybean oil treatment.
The effects of three highly refined petroleum spray oils and of ambient vapor pressure on net CO2 assimilation (A) and stomatal conductance of water vapor (gs) of single grapefruit (Citrus paradisi Macf.) leaves were investigated. Overall, gs of various-aged leaves was decreased by a large leaf-to-air vapor pressure difference (VPD). In the first experiment, oils with midpoint distillation temperatures (50% DT) of 224, 235, and 247C were applied with a hand atomizer at concentrations of 0, 1%, and 4% oil emulsions in water and 100% oil, all with 0.82% surfactant (by volume). There was a tendency for oils of the two higher DT to decrease net gas exchange during a subsequent 12 days, but significant differences could not be attributed to oil DT. Both A and gs were reduced by the two higher concentrations of oil mixtures. In the second experiment, a commercial airblast sprayer was used to apply the 224C oil at 4% or the 235C oil at 2% and 4% mixtures plus surfactant under field conditions. There were no significant effects of oil treatments on net gas exchange of leaves either measured under moderate VPD outdoors 1 day after spraying or under low VPD in the laboratory 2 days after spraying. No visible phytotoxic symptoms were observed in either experiment.
Field-grown dogwood trees in a commercial nursery were sprayed with 0%, 1%, or 2% soybean oil emulsified with Latron B-1956 at 2-week intervals from 10 June until 19 Aug. 1998. In 1999, dogwood trees were sprayed with 0%, 1%, 1.5%, 2%, or 2.5% emulsified soybean oil at 2-week intervals from 22 June until 26 Aug. The trials had treatments arranged in randomized complete-block designs with eight trees per block and six and four replications in 1998 and 1999, respectively. Disease severity of powdery mildew was estimated using the following scale: 0 = healthy, 1 < 2%, 2 < 10%, 3 < 25%, 4 < 50%, 5 > 50%, and 6 = 100% of foliage with symptoms or signs of powdery mildew. In 1998, trees sprayed with soybean oil had higher net photosynthesis rates and more caliper and height growth than control trees. Untreated trees and ≈25% of foliage infected with powdery mildew on 8 July, while trees sprayed with 1% or 2% soybean oil had about 2% of leaves infected. In 1999, the powdery mildew was already present on foliage (wet spring) when the first application of oil was made. Repeated sprays of soybean oil did not reduce the incidence of powdery mildew. Thus, soybean oil appeared to provide protective control of powdery mildew but not curative control of a heavy infestation of the fungi. Photosynthesis was increased by soybean oil for the first month of spraying in 1999, but did not differ after that. Repeated applications of even the high rates of oil did not cause phytotoxicity.
Previous research indicated that soybean oil effectively controlled insects and mites on ornamentals. In some conditions, emulsified oil sprays have also been shown to cause phytotoxicity. The objective of this research was to determine which soybean oil emulsions and/or emulsifiers produced the least amount of phytotoxicity on miniature roses. Greenhouse-grown `Fashion' (pink), `Fiesta' (fuchsia), `Tender' (white), `Orange' (red), and `Bronze' (yellow) miniature roses in trade-gallon containers were sprayed once in late fall 1998. Treatments included: 1) water (control); 1% concentrations of commercial soybean oil formulations of 2) Soygold 1000 and 3) Soygold 2000 (Ag Environmental Products), 4) Emulsion A and 5) Emulsion B (Michigan Molecular Institute); 1% soybean oil emulsified with 6) 0.1% Ballistol (F.W. Klever, Germany), 7) 0.1% ERUCiCHEM (International Lubricants), 8) 0.1% ERUCiCHEM mixed with 0.01% lecithin (Chem Service), 9) 0.1% soy methylester (Michigan Molecular Institute), 10) 0.06% Atlox and 0.04% Tween (ICI Americas), 11) 0.1% E-Z-Mulse (Florida Chemical Company), or 12) 0.1% Latron B-1956 (Rohm & Haas). The emulsifiers were also tested alone for phytotoxicity to rose foliage. None of the emulsifiers caused significant damage. Soybean oil emulsified with E-Z-Mulse did not cause significant phytotoxicity as indicated by chlorosis of foliage. The commercially prepared Emulsion A, Soygold 1000 and Soygold 2000 caused slight phytotoxicity. Emulsion B and soybean oil plus Latron B-1956 caused moderate phytotoxicity. The soybean oil-Ballistol emulsion was the most phytotoxic. Cultivars varied in sensitivity (P < 0.01) to soybean oil emulsions (listed in the order of increasing sensitivity): `Orange', `Fashion', `Bronze', `Fiesta', and `Tender'.
Laboratory and field application methods of (methyl 1-(butylcarbamoyl)-2 benzimidazolecarbamate) (benomyl) and oil were evaluated for their influence on net photosynthesis of leaves of potted apple trees. Superior 70-second viscosity oil applied as a dip caused a significant reduction in net photosynthesis of young leaves at both the 1.26 ml and 2.52 ml/liter levels, with the greater reduction at the higher level. Benomyl alone or in combination with oil had no influence on net photosynthesis. Spray application in the laboratory or by commercial field sprayers had no effect on net photosynthesis of fully expanded leaves.