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D.E. Deyton, C.E. Sams, and J.C. Cummins

Treatments of 0, 10, 20, 30, or 40% (v/v) refined (salad) or crude soybean oil or 0, 5, 10, 15, or 20% petroleum (dormant) oil at 0, 5, 10, 15, or 20% were sprayed until drip on `Smoothee' apple trees on 27 February 1991. The internal carbon dioxide concentration was elevated and the oxygen content reduced within one day in buds-twigs treated with oil and remained influenced for up to 12 days. All oil treatments delayed fruit bud development. The lowest tested concentration of soybean oil (either crude or refined) resulted in the greatest delay in bud development and the greatest delay in bloom (approximately 4 days). Crude soybean oil treatment resulted in less damage to flower buds than petroleum oil.

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D.E. Deyton, C.E. Sams, J.C. Cummins, R.E. Myers, and M.A. Halcomb

Hand-defoliation of field-grown `Golden Delicious' apple and `Bradford' pear nursery trees before autumn digging is a major production cost. One-year-old field-grown trees were sprayed to runoff on 18 Oct. 1994 with; 1) 1% FeEDTA, 2) 1% CuEDTA, 3) 1% ZnEDTA, 4) 100 ppm Harvade, 5) 50 ppm Dropp, 6) 500 ppm Folex, or 7) 2.5% EDTA or 8) leaves were removed by hand or 9) leaves left on trees (control). Treatments were arranged in a randomized complete-block design, with three trees/plot and four replications. Leaves on each tree were counted before treatment and 7, 14, 21, 28, and 35 days after treatment (DAT). One tree per plot was dug, stored until February and grown the following summer. Nontreated apple and pear trees had 13% and 38% defoliation, respectively, 35 DAT. CuEDTA treated apple trees had 62% and 93% defoliation 7 and 14 DAT, respectively. Pear trees treated with Cu had 18% and 100% defoliation 7 and 14 DAT, respectively. Treatment with FeEDTA resulted in 96% defoliation of pear within 7 DAT but only 57% defoliation of apple 35 DAT. ZnEDTA, Harvade, Folex, or Dropp did not significantly promote defoliation. Copper-treated apple trees had less budbreak than nontreated trees but similar budbreak as hand-defoliated trees. None of the treatments influenced budbreak of pear. None of the treatments affected the cumulative dry weight of trees at the end of the next growing season.

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D.E. Deyton, C.E. Sams, J.C. Cummins, and D.W. Lockwood

One-year-old peach trees in nurseries at McMinnville, Tenn., were exposed to –11C on 5 Nov. 1991 before digging. The nursery owners were concerned about the relationship of tree cambium browning to potential tree performance after planting. A color scale [0 = nondamage (white) to 6 = severely damaged (brown)] showing discolored cambium of peach nursery trees was developed to rate damage. Browning was rated at 8 cm above graft union. Five trees each of nine cultivars with chill hour requirements ranging from 175 to 1050 were rated. Cultivars with <500 chill hour requirement had higher ratings. Ten `Harbite' trees from each of six size grades were rated. Trees in grades of 30- to 90-cm height had less cambium browning than trees in grades of 90 to 152 cm height. In Dec. 1992, 1-year-old `Red Globe' trees were exposed to –6 (minimum field temperature), –15, –18, –24, –30, or –35C in a programmable freezer. A subsample of five trees per treatment was rated for browning 1 day after treatment and a second subsample rated in mid February. Trees in a third subsample were grown in a nursery the following summer. Slight browning (rating = 1.6) was evident soon after exposure to –24C; however, severe browning was evident on trees exposed to –30 or –35C. Trees exposed to temperature more than –24C did not differ in height, trunk diameter, or dry weight at the end of the growing season, however trees exposed to –30 or –35C did differ. In a similar experiment, `Juneprince' trees exposed to –18C had slight cambium browning (rating = 1.2) but trees died.

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A.L. Lancaster, C.E. Sams, D.E Deyton, and J.C. Cummins

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'.

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R.E. Moran, D.E. Deyton, C.E. Sams, J. Cummins, and C.D. Pless

Soybean oil can be used as an alternative pesticide for fruit trees. Two separate studies were conducted to determine the effects of oil concentration on leaf phytotoxicity and net CO2 assimilation (ACO2). In one study, concentrations of 0%, 2%, 4%, and 6% soybean oil in water were applied to individual shoots with a hand-held mist bottle. In the second study, 0%, 1.0%, and 1.5% were applied to whole trees with an airblast sprayer. Petroleum oil was applied as a separate treatment. Net CO2 assimilation was measured on single leaves. Oil residue was removed from the leaf with chloroform, dried, and weighed. Chlorosis and defoliation occurred with applications of 4% and 6% soybean oil. No visible phytotoxicity occurred with 2% or less oil. Net CO2 assimilation decreased as the rate of soybean oil increased from 0% to 4% oil, but there was no difference between 4% and 6%. Net CO2 assimilation decreased with increasing oil concentration from 0% to 1.5% and recovered to the rate of the control on day 7. Net CO2 assimilation was negatively related to oil residue. At an equivalent oil residue, there was no difference in ACO2 between petroleum and soybean oil. Below a residue of 0.15 mg·cm–2, foliar phytoxicity did not occur. Reductions in ACO2 were small and did not last longer than 7 days if residues were ≤0.10 mg·cm–2.

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B.R. Bondada, C.E. Sams, D.E. Deyton, and J.C. Cummins

Environmental factors such as rainfall may reduce the efficacy of foliar-applied soybean [Glycine max (L.) Merrill] oil in reducing pest mortality. Greenhouse studies were conducted to investigate the influence of rain on the retention of soybean oil and the influence of soybean oil and rainfall on surface morphology of apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] and peach [Prunus persica (L.) Batsch (Peach Group)] leaves and stems. `Contender' peach and `Golden Delicious'/Malling 27 apple trees were grown in 19 L pots in a greenhouse (23 ± 9 °C) and sprayed with soybean oil (1%) emulsified with the adjuvants Latron B-1956 or K1. Twenty-four hours after treatment, the trees were subjected to simulated rainfall of 0.0, 0.25, 1.25, or 2.54 cm. A negative linear relationship existed between rainfall and oil retention. Peach leaves receiving 0.25, 1.25, and 2.54 cm rainfall retained 81%, 38%, and 18% of the applied oil, respectively. Oil retention by apple leaves was also negatively related to rainfall. For both species, a negative linear relationship existed between oil retention on stems and rainfall. There was no effect of emulsifier on retention of 1% soybean oil after rain on apple leaves or on the retention of 8% to 11% soybean oil on the stems of apple and peach. Scanning electron microscopy revealed that epicuticular wax occurred as striations on apple and peach leaves. The wax morphology on peach and apple stems appeared as thin plates and platelets, respectively. The wax morphology of leaves and stems of both trees was not affected either by the soybean oil emulsions or rain. Both emulsions induced stomatal closure in leaves and peach stems, however, stomates opened after rainfall of 1.25 or 2.54 cm. The lenticels appeared to be unaffected by either emulsion. Results illustrate that rainfall of 2.54 cm washed off a major portion of the applied oil. Thus, respraying may be needed under natural climatic conditions with rainfall ≥2.54 cm to restore the efficacy of applied soybean oil.