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Pascal Braekman, Dieter Foqué, Marie-Christine Van Labeke, Jan G. Pieters, and David Nuyttens

Gilles (1992) showed that an electrostatic reduced-volume application of permethrin insecticide to greenhouse-grown chrysanthemums resulted in significantly higher spray deposition compared with the conventional high-volume application. However, this

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Ockert P.J. Stander, Jade North, Jan M. Van Niekerk, Tertia Van Wyk, Claire Love, and Martin J. Gilbert

evaluated the effects of NPN on foliar spray deposition, leaf mineral nutrient concentration, fruit yield and quality, and rind surface damage of ‘Nadorcott’ mandarin fruit. Monitoring of two important insect pest species was performed during the experiment

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Gary VanEe, Richard Ledebuhr, Eric Hanson, Jim Hancock, and Donald C. Ramsdell

Most highbush blueberries (Vaccinium corymbosum L.) in Michigan are treated annually with fungicides and insecticides with several types of sprayers. The goal of this study was to determine how sprayer type, pruning severity, and canopy development interact to affect spray deposition patterns. Deposition was measured as the percentage of the surface area of card targets that was covered following applications of black dye. Light measurements indicated that the canopy of blueberry bushes, regardless of pruning treatment, closed by the middle of June, and light levels within the canopy changed little from then until fruit harvest in August. A standard airblast sprayer that pushed spray up and through bushes provided acceptable deposition in all parts of the canopy early in the season, but later in the season, coverage was poor in the top and sides furthest from the sprayer. An above-row sprayer with fan-driven micronozzles also provided acceptable coverage throughout the bushes early in the season, but once the canopy had closed, coverage was poor in the bottom of the bush. Both sprayers were operated in bushes receiving light, moderate, and heavy pruning. The more severe pruning regimes increased the amount of spray deposited from the above-row sprayer, but not from the airblast sprayer.

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Heping Zhu, James Altland, Richard C. Derksen, and Charles R. Krause

strategies, confirmation of the actual spray coverage and spray deposition on targets under field conditions is required ( Bache and Johnstone, 1992 ). The spray coverage required to effectively control pests has been studied for other crops ( Falchieri et al

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Dieter Foqué, Jan G. Pieters, and David Nuyttens

conditions, the spray deposition, penetration, and uniformity of the spray applied using a manually pulled horizontal spray boom was evaluated and compared with spray gun applications. The potential effect of the crop's density was taken into account as well

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S.J. McArtney and J.D. Obermiller

delivering an equivalent total spray volume. Foliar spray deposition was determined by placing three WSP at each of six different heights in the test tree. Spray coverage was assessed by image analysis of water-sensitive papers (WSP; Spraying Systems) stapled

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Ed Stover, Dominick Scotto, Chris Wilson, and Masoud Salyani

Foliar application of spray materials is an integral component of commercial citrus production. An intensive assessment of spray application practices has been stimulated by low fruit value and increased concern about potential surface water contamination in the Indian River citrus region of Florida. Many publications report research results regarding distribution of spray materials within orchards and off-target deposition, but interpretation is challenging because so many factors influence spray results, and integrating this information into practical recommendations is difficult. Canopy geometry and density are prominent factors contributing to variable deposition and spray drift. Environmental factors such as temperature, relative humidity, wind speed, and wind direction also greatly influence spray deposition and drift, and substantial changes can occur within seconds. In addition the physical and/or mechanical set up of the sprayer interact significantly with the other factors. A better understanding of these interactions should help growers optimize spray effectiveness and efficiency while reducing potential off-target effects.

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Ed Stover, Chris Wilson, Dominick Scotto, and Masoud Salyani

Parts I and II of this series revealed substantial opportunities for improving spraying of Indian River citrus (Citrus spp.). In this segment of our work we develop guidelines for growers to select the spray parameters providing an optimal balance between efficiency and efficacy while minimizing environmental contamination.

It is proposed that these guidelines could be codified in a simple expert system to make them easier to use. We propose that understanding limiting conditions may be the key to choosing spray options. Wind is a major factor influencing spray deposition and offtarget drift. Based on weather records, wind speeds below 5 mph (8.0 km·h-1) are only routinely observed from 2000 HR until 0800 HR, making night spraying a good choice for low-volume applications. The importance of adjusting sprayer set-up for individual groves is demonstrated, with economic estimates of the cost of failing to make these adjustments. Routine use of careful sprayer adjustments is also likely to reduce off-target drift. Improvements in equipment and spray chemicals are also discussed. Use of non-orchard buffer areas and/or windbreaks appear to offer considerable opportunity for reducing off-site spray movement.

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Celeste Welty, Sandra Alcaraz, and H. Erdal Ozkan

Insecticide application techniques were evaluated to find the most effective way to spray contact insecticides to control aphids on leaf crops under field conditions. A hydraulic boom sprayer was tested with several nozzle types, nozzle positions, and pressures, and compared with an electrostatic sprayer and a controlled droplet applicator (CDA). Spray deposition in the canopy and drift were evaluated with moisture-sensitive cards. Trials were conducted on collards and red leaf lettuce in 1989, mustard greens in 1990, and turnip greens in 1991. Green peach aphid [Myzus persicae (Sulzer)] was the major species in all trials. Among hydraulic boom treatments in all trials, aphid control was not significantly different when insecticide applied at 60 psi (414 kPa) was delivered by hollow cone, twin flat-fan, or standard flat-fan nozzles mounted directly on the boom. In most trials, hollow cones were more effective when mounted on drop pipes and directed sideways into rows than when mounted on the boom and directed over rows. Hollow cone nozzles used at 150 psi (1035 kpa) vs. 60 psi did not control aphids significantly better, but higher pressure caused significantly more drift. Contact insecticide applied by an electrostatic sprayer controlled aphids somewhat less satisfactorily than by a conventional hydraulic sprayer. Insecticide applied by a CDA controlled aphids the same as by a hydraulic boom sprayer but with slightly less drift. The desired objective of maximum aphid control, good coverage of downward-facing surfaces in the canopy, and minimum drift was most consistently provided by the hydraulic boom sprayer with hollow cone nozzles on drop pipes directed sideways into the canopy using a pressure of 60 psi.