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Charles C. Reilly, Michael W. Hotchkiss, and Kathryn C. Taylor

Pesticide application in peach (Prunus persica) orchards with a commercial airblast sprayer was compared to that of an air assisted rotary atomizer (AARA), low-volume sprayer during the 2000 through 2003 seasons. The two technologies were employed during early season petal fall applications, shuck split applications and standard cover sprays using phosmet, sulfur, propiconazole, chlorothalonil, azoxystrobin and captan. Ripe fruit, picked 1 day prior to first harvest each season were rated for peach scab (Cladosporium carpophilum), brown rot (Monilinia fructicola), insect (Hemipteran) damage (cat facing), and blemishes. Differences in brown rot, insect damage, and blemish ratings were not detected between the treatments for each of the four seasons. Differences were detected during the 2000 and 2001 seasons for peach scab, with the AARA sprayer plots having a higher incidence. Spray coverage was quantitatively evaluated with Rhodamine B dye by leaf rinses that indicated there was equivalent coverage for each application method. Phosmet residue detection on trees of the treated rows was also equivalent from each method. Phosmet off-target spray movement (drift) was reduced 59% one row away from the treated row and 93% in the fifth row from the treated row by the AARA sprayer compared to airblast sprayer drift.

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Martin J. Bukovac

The importance of spray application and the role of spray additives are reviewed in reference to increasing the effectiveness of plant growth regulators (PGR). The spray application process is composed of a number of interrelated components, from formulation of the active ingredient into a sprayable, bioactive solution (emulsion/suspension), to atomization, delivery, retention, and penetration into the plant tissue. Each of these events is critical to performance of the PGR. Also, each can be affected by spray additives, particularly adjuvants, which may be incorporated in the formulation of the active ingredient or added to the spray mixture. The role of the individual components and effects of spray adjuvants, particularly surfactants and fertilizer adjuvants, on the component processes are discussed.

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Thomas W. Walters, LeRoy A. Ellerbrock, Jan J. van der Heide, James W. Lorbeer, and David P. LoParco

Greenhouse and field methods were developed to screen Allium spp. for resistance to botrytis leaf blight (causal agent Botrytis squamosa Walker). In greenhouse evaluations, plants were sprayed with laboratory-grown mycelial fragment inoculum and were incubated at 20C in a chamber with an atomizing fogger. For field inoculations, a portable fog system with windbreaks was erected around experimental plots, and the plants were sprayed with the inoculum on evenings when windless, temperate (18 to 22C) conditions were forecasted. The most effective mycelial fragment inoculum was <21 days old and had ≈45 to 50 colony-forming units/μl, resulting in an absorbance at 450 nm of 0.2 to 0.3. Rubbing the wax cuticle from leaves was essential to disease development in greenhouse but not in field experiments. Evaluations of eight Allium species, including 55 A. cepa L. accessions, were in agreement with previous studies.

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J.P. Syvertsen and M. Salyani

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.

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Thomas W. Walters, Leroy A. Ellerbrock, Jan J. van der Heide, James W. Lorbeer, and David P. LoParco

Greenhouse and field methods were developed to screen Allium spp. for resistance to Botrytis leaf blight (caused by Botrytis squamosa Walker). In the green-house, plants were sprayed with laboratory-grown inoculum and incubated in a temperature-controlled enclosure containing an atomizing mist system. For field inoculations, a portable misting system with windbreaks was erected, and the plants were sprayed with laboratory-grown inoculum. Greenhouse and field incubation conditions maintained leaf wetness without washing inoculum from the leaves. Botrytis leaf blight symptoms in greenhouse and field evaluations were identical to symptoms in commercial onion fields. A total of 86 selected USDA Allium collection accessions were evaluated using these methods. All A. fistulosum accessions and A. roytei were highly resistant to immune, as were most accessions of A. altaicum, A. galanthum, A. pskemense, and A. oschaninii. Nearly all of the A. vavilovii and A. cepa accessions were susceptible. However, one A. cepa accession (PI 273212 from Poland) developed only superficial lesions, which did not expand to coalesce and blight leaves. This work confirms previous reports of Botrytis leaf blight resistance in Allium spp., and suggests that strong resistance exists with A. cepa.

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Clint Hoffmann, Brad Fritz, Dan Martin, Ryan Atwood, Tim Hurner, Mark Ledebuhr, Matt Tandy, John L. Jackson, and Gail Wisler

atomization for the London Fog model 18–20 sprayer (London Fog, Long Lake, MN). Table 3. Effects of a.i. and engine speed on spray atomization for the Curtec sprayer (Curtec of Florida, Vero Beach, FL). Table 4. Effects of a.i. and engine speed on spray

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Robert M. Pyne, Adolfina R. Koroch, Christian A. Wyenandt, and James E. Simon

humidity and leaf wetness were maintained by two Trion 707U Series atomizing humidifiers (Trion Air Purification Systems, Sanford, NC) on opposite ends of the enclosure ( Fig. 1 ). A mist chamber, consisting of a partial enclosure with an opening at the

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airblast sprayers (AB) that produce drift away from the target crop. The labor associated with spray operations is costly. Reilly et al. (p. 555) found that low-drift, air-assisted, rotary-atomizer sprayers (AARA) were as effective as AB, without excessive

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Mingyuan Xu, Yingwei Wang, Qianbo Wang, Shenglei Guo, Yang Liu, Jia Liu, Zhonghua Tang, and Zhenyue Wang

) equipped with an Electrospray Ionization source with the following operating parameters: cone voltage of 3 kV and ion source atomization temperature of 500 °C; 25 psi atomizing gas and 20 psi air curtain gas. The ion pair, cluster voltage, collision voltage

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Lauren Fessler, Amy Fulcher, Dave Lockwood, Wesley Wright, and Heping Zhu

that is atomized into droplets of 45 µm mass-median-diameter by high-speed air flow from the air blower ( Superb Horticulture, 1994 ). Because of the air shearing method to atomize spray liquids for this sprayer, droplet sizes varied with liquid flow