Handgun treatments of abamectin and oil applied between mid-June and late August caused distinct epidermal rings where drops of spray liquid dried on the surface of pear fruit (Pyrus communis L.). The severity of epidermal injury was related to the concentration of oil in the abamectin spray mixture (abamectin applied without oil caused no fruit damage). Of six pear cultivars tested, `Anjou' was most susceptible to injury, followed by `Cornice' and `Bartlett'. `Sensation Red Bartlett', `Bosc', and `Seckel' showed little or no phytotoxicity symptoms from abamectin and oil treatments with oil concentrations from 0.125% to 2.0% (v/v). On sensitive cultivars, the concentration of oil should not exceed 0.25% (v/v) when combined with abamectin to reduce the risk of epidermal injury. Oil at 0.25% provides for adequate leaf penetration of abamectin and results in commercially acceptable spider mite (Tetranychus urticae Koch) control. Chemical names used: avermectin B1 (abamectin).
Abstract
Leaf number, area and chlorophyll content, and specific leaf weight were greater in light-exposed spurs of ‘Hartley’ walnut (Juglans regia L.) than those grown in the shade. Starch content increased early in the season in shaded spurs, but the accumulation ceased while the nuts stored dry matter. In exposed spurs, starch increased steadily until harvest. After harvest, starch level decreased in exposed and shaded spurs. Light intensity did not affect percentage composition of spurs and fruit with respect to carbohydrates or oil content in kernels. Increased exposure to light resulted in higher percentage of return bloom, greater spur growth, and more pistillate flowers per spur the following season.
Pecans, because of their high oil and polyunsaturated fatty acid content, have a relatively short shelf life due to oxidation of the oil. Using a nondestructive supercritical CO2 extraction process, we evaluated oil reduction as a means for pecan shelf life extension. Pecan halves were extracted under sufficient conditions for 22% and 28% oil reduction, and then stored in modified-atmosphere packages with 21% O2 at 22C for up to 37 weeks. Kernel hexanal content and sensory rancid flavor were monitored at various times throughout the study. The resistance of oils to oxidation, indicated by the onset of sustained hexanal production, was increased from 6 weeks for full-oil halves, to 18 weeks for 22% reduced-oil halves, to 22 weeks for 28% reduced-oil halves. Objectionable rancid flavor was detected by the 22nd week of storage for full-oil pecans. Reduced-oil pecans never developed objectionable rancid flavor. Supported by USDA grant 93-341508409, OCAST grant AR4-044, and the Oklahoma Agricultural Experiment Station.
An experimental steam distillation unit has been designed, built, and tested for the extraction of essential oils from peppermint and spearmint. The unit, using a 130-gal (510-liter) distillation tank, is intermediate in size between laboratory-scale extractors and commercial-sized distilleries, yet provides oil in sufficient quantity for industrial evaluation. The entire apparatus-a diesel-fuel-fired boiler, extraction vessel, condenser, and oil collector-is trailer-mounted, making it transportable to commercial farms or research stations. Percentage yields of oil per dry weight from the unit were slightly less than from laboratory hydrodistillations, but oil quality and terpene composition were similar.
Applications of soybean oil to dormant peach [Prunus persica (L.) Batsch] trees were tested for prebloom thinning of flower buds in five separate experiments. Data were combined from experiments in which 2.5% to 20% emulsified soybean oil was sprayed on `Belle of Georgia' or `Redhaven' trees. The number of dead flower buds was concentration-dependent with maximum bud kill of 53% occurring with application of 12% soybean oil. The amount of thinning was fairly consistent from year to year, ranging from 34% to 51% when 10% soybean oil was applied, but was less consistent when 5% was applied, ranging from 6% to 40%. Overthinning by midwinter applications of soybean oil occurred in one experiment when bud mortality on nontreated trees was 40% due to natural causes. Mild to moderate spring freezes occurred in three experiments, but did not reduce yield more in soybean oil–thinned than in nontreated trees. Flower bud survival was improved when trees were sprayed with 10% or 12% soybean oil prior to a –4 °C spring frost. Applications of soybean oil to dormant trees thinned flower buds, reduced the amount of hand thinning required, and hastened fruit maturity.
Abstract
Peppermint (Mentha piperita L. cv. Black Mitcham) grown in a controlled environment under simulated sprinkler irrigation produced essential oil in 23% lower yield than did identical plants grown under simulated furrow irrigation. With spearmint (M. spicata L.) sprinkler irrigation produced oil yields 34% lower than furrow irrigation. When the sprinkler system was on, the rate of essential oil evaporation increased 4 to 5-fold over the rate increase observed in furrow irrigated controls, and an elevated rate of evaporation persisted for several hours after cessation of sprinkling. Physical damage to the oil glands by falling water droplets did not appear to be the major cause of increased evaporation, as studies in water-saturated chambers showed that high humidity alone could cause rapid rates of oil evaporation. Apparently, wetting of the foliage under sprinkler irrigation results in hydration and swelling of the cuticle enclosing the oil glands. Consequently, the permeability of the cuticular membrane may be altered, allowing more rapid evaporation of the volatile oil. The increased rate of oil evaporation in sprinkler irrigated mint may be one of the factors responsible for lowered yields with this irrigation method.
Information about oil and fatty acids in tepary bean (Phaseolus acutifolius A. Gray) seed, a promising alternative crop for the mid-Atlantic region of U.S., is largely unknown. Such information is needed to assess the food and feed potentials of tepary bean seed. We determined the concentrations of oil and fatty acids in seed produced by eight tepary bean genotypes planted at three different dates each during 1997 and 1998 at Ettrick, Va. Tepary bean seeds contained 1.8% oil as compared to literature values of 1.3%, 1.1%, and 1.1% for navy, kidney, and pinto beans, respectively. Tepary bean seed oil contained 33% saturated, 67% unsaturated, 24% monounsaturated, and 42% polyunsaturated fatty acids. Planting dates and genotypes did not affect oil concentration. Neb-T-14 was identified to be a desirable genotype based on a low concentration of saturated and a high concentration of polyunsaturated fatty acids. Based on concentrations of oil and fatty acids, tepary bean seeds compared well with those of navy, kidney, and pinto beans.
The content of essential oil, thymol, and carvacrol in a thymol-type of clonally selected thyme plants during different developmental stages were investigated under greenhouse and field conditions. Plants in the greenhouse were grown from July to November, under natural light and natural light supplemented by a PPF of 200 μmol·m–2·s–1, provided by HPS lamps, while plants in the field were studied from June to November. Shoot yield and the accumulation of the active principles from greenhouse-grown plants were determined by harvesting the plants at 40-, 60-, and 120-day intervals, while field-grown plants were harvested in August, September, October, and November. Essential oil content, qualitative and quantitative changes in the oil were determined by subjecting the samples to steam distillation and subsequent gas chromatographic analysis. There were important changes in shoot yield, essential oil, thymol, and carvacrol content in the course of plant development. After 120 days of growth under greenhouse conditions, the essential oil content increased by >150%, while thymol content increased by ≈200% compared with the 40-day-old plants. We found some differences in oil content, thymol, and carvacrol accumulation between field- and greenhouse-grown plants. The pattern of crop yield and the accumulation of the major active substances under field and greenhouse conditions are presented and discussed.
Mature `Picual' olive (Olea europaea L.) trees growing in two different localities of Córdoba and Jaén provinces, southern Spain, were subjected to annual applications of 0, 0.12, 0.25, 0.50, or 1.0 kg N/tree in the Cordoba's experiment, and to 0 or 1.5 kg N/tree in the Jaén's experiment. Nitrogen was applied 50% to the soil and 50% through foliar application in Córdoba, and 100% to the soil in Jaén. Three years after the initiation of treatments, when the trees showed differences among them in nitrogen content, fruit were sampled at maturity from each experimental tree during six consecutive seasons to determine the effect of nitrogen fertilization on olive oil quality. Tree nitrogen status was always above the threshold limit for deficiency even in control trees, indicating that most treatments caused nitrogen over fertilization. Nitrogen in excess was accumulated in fruit and, consequently, polyphenol content, the main natural antioxidants, significantly decreased in olive oil as nitrogen increased in fruit. The decrease in polyphenols induced a significant decrease in the oxidative stability of the oil and its bitterness. Tocopherol content, on the contrary, increased with nitrogen application, mainly by an increase in α-tocopherol, the main component in the olive oil. No effect was found on pigment content, particularly carotenoid and chlorophyllic pigments, neither on fatty acid composition.
Four-year-old `Gala' and `Widjit' apple trees with significant apple aphid populations were sprayed to runoff on 13 May 1994 with 0%, 0.5%, 1.0%, or 2.0% (v/v) emulsified degummed soybean oil (SO) or with 1.0% petroleum (dormant) oil (PO). Treatments were arranged in a randomized complete-block design with five single-tree replications. Apple aphid populations were determined on 10 tagged shoots per tree. The top fully expanded leaf of two randomly selected shoots per tree were tagged and net photosynthesis (Pn) and transpiration (Tr) measured. Trees treated with SO or PO had <20% as many aphids after treatment as nontreated trees. Trees treated with 2% SO had lower Pn and Tr than the control for 18 days after treatment. Spraying 0.1% or 0.5% SO caused less initial reduction of Pn than 2.0% SO, and the effect was shorter lasting. Four-year-old `Oregon Spur' and `Empire' were sprayed with 0%, 0.1%, 0.5%, 1.0% SO or PO on 26 June. Treatments were arranged in a randomized complete-block design with four single-tree replications. Pn rates of trees treated with 0.1% to 1.0% soybean oil were <40% of nontreated trees the day after treatment, but recovered to >80% of control in 5 days.