The tomatopotato psyllid incurs high control costs through intensive spraying and other treatments A field study was conducted in March 2012 in Pukekohe New Zealand to evaluate the pesticide deposition potential of five different spray delivery systems The treatments included a conventional boom a canopy submerged drop sprayer combination a pneumatic electrostatic spraying system an airassisted rotary atomizer and a highvolume airassist boom Each system was calibrated for appropriate spray volume rates between 167 and 400 litres/ha Rhodamine WT fluorescent dye used as a tracer was sampled on folded Kromekote sampling cards oriented flat and horizontally above central to and below the canopy Spray coverage rates were quantified at designated heights adjacent to leaves to assess deposition throughout the potato canopy All treatments that consisted of one or more novel technologies consistently gave higher coverage to the underside of the potato leaves than with the conventional boom

Solid Set Canopy Delivery Systems (SSCDS) are fixed agrochemical delivery systems composed of a network of micro-sprayers/nozzles distributed in perennial crop canopies. A previous SSCDS design composed of a 3-tier configuration using hollow cone sprayer nozzles has been shown to provide excellent coverage and deposition in high-density apple orchards. However, the hollow cone nozzles substantially increases the initial system installation costs. This study evaluated the effect of irrigation micro-emitters replacement on spray deposition, coverage and off-target drift. A micro-emitter used in greenhouse irrigation systems was duly modified to enhance its applicability with SSCDS. After laboratory assessment and optimization of the micro-emitters, a replicated field study was conducted to compare 3-tier SSCDS configured with either of modified irrigation micro-emitters or traditional hollow cone nozzles. Canopy deposition and off target drift were evaluated using a 500 ppm fluorescent tracer solution sprayed by the field installed systems and captured on mylar collectors. Spray coverage was evaluated using water sensitive papers. The overall canopy deposition and coverage for treatment configured with modified irrigation micro-emitters (955.5 ± 153.9 [mean ± standard error of mean] ng cm−2 and 22.7 ± 2.6%, respectively) were numerically higher than the hollow cone nozzles (746.2 ± 104.7 ng cm−2 and 19.0 ± 2.8%, respectively). Moreover, modified irrigation micro-emitter SSCDS had improved spray uniformity in the canopy foliage and on either side of leaf surfaces compared to a hollow cone nozzle. Ground and aerial spray losses, quantified as deposition, were numerically lower for the modified irrigation micro-emitter (121.8 ± 43.4 ng cm−2 and 0.7 ± 0.1 ng cm−2, respectively) compared to the traditional hollow cone nozzle (447.4 ± 190.9 ng cm−2 and 3.2 ± 0.4 ng cm−2, respectively). Overall, the modified irrigation micro-emitter provided similar or superior performance to the traditional hollow cone nozzle with an estimated 12 times reduction in system installation cost.

Optimally configured solid set canopy delivery systems (SSCDS) can provide adequate spray performance in high-density apple orchards with a minimized risk of off-target pesticide drift. SSCDS configured in a shower-down emitter arrangement have been reported to be the simplest and most economical system. However, existing off-the-shelf emitters used in shower-down configurations have resulted in minimal deposition in lower canopy zones. Therefore, this study was focused on the modifications of off-the-shelf emitters to obtain a desirable spray pattern for adequate spray deposition in all the canopy zones. The modifications include redesigning the impact plate of two existing micro-emitters. Field tests were conducted to evaluate the spray performance of SSCDS with the non-modified emitters (treatment: SD1 and SD3) and contrast the results with modified emitters (treatment: SD2 and SD4). While the treatments SD1 and SD3 had off-the-shelf emitters with swivel plate and static spreader, respectively, the treatment SD2 and SD4 had similar emitters with modified impactor plates. In each treatment block, the apple canopy was divided into six zones and sprayed with a 500 ppm fluorescent tracer solution. Mylar cards and water-sensitive paper samplers were placed on the adaxial and abaxial leaf surfaces in each canopy zone to quantify spray deposition and coverage, respectively. The SSCDS treatments retrofitted with modified emitters, i.e., SD2 and SD4, were observed to have uniform and numerically higher deposition and coverage compared to SD1 and SD3. The SSCDS treatment with modified static spreader (i.e., SD4) resulted in the highest overall spray deposition (1405.7 ± 156.4 ng cm−2 [mean ± standard error]) with improved mid (1121.6 ± 186.9 ng cm−2) and bottom (895.6 ± 149.3 ng cm−2) canopy deposition. Overall, the proposed emitter modification assisted in improved SSCDS spray performances and may be a way forward toward large-scale emplacements of such systems.

The asian citrus psyllid [Diaphorina citri (Sternorrhyncha: Psyllidae)] is a detrimental pest to citrus (Citrus spp.) crops when it serves as a vector of the pathogen that causes greening (huanglongbing). Transmission of this disease causes mottling, chlorosis, dieback, and reductions in fruit size and quality. Citrus producers have found that many pesticides, when applied properly, are very effective at suppressing or eliminating asian citrus psyllids in groves. Due to the threat of greening, several pesticides have been granted Special Local Needs registration for use in the state of Florida if the product is sprayed with a volume median diameter of 90 μm or greater. A number of studies involving numerous citrus sprayers and a.i. were conducted to determine the droplet sizes generated by different sprayers operating under user-established settings and the adjustments required to those settings for the sprayers to meet the 90-μm requirement. In the sprayer tests, it was found that reductions in engine speed or increases in flow rate were required to increase droplet sizes to meet the product label-required droplet size. As the equipment tested here represent the most typical application equipment used in Florida for asian citrus psyllid control, these results will provide applicators, growers, and extension agents with general guidelines to ensure that spray systems are operated in a manner that complies with label restrictions.

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