Determining the drift potential of Venturi nozzles compared with standard nozzles across three insecticide spray solutions in a wind tunnel.

BACKGROUND: Previous research has sought to adopt the use of drift-reducing technologies (DRTs) for use in field trials to control diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae) in canola (Brassica napus L.). Previous studies observed no difference in canopy penetration from fine to coarse sprays, but the coverage was higher for fine sprays. DBM has a strong propensity to avoid sprayed plant material, putting further pressure on selecting technologies that maximise coverage, but often this is at the expense of a greater drift potential. This study aims to examine the addition of a DRT oil that is labelled for control of DBM as well and its effect on the drift potential of the spray solution. The objectives of the study are to quantify the droplet size spectrum and spray drift potential of each nozzle type to select technologies that reduce spray drift, to examine the effect of the insecticide tank mix at both (50 and 100 L ha(-1) ) application rates on droplet size and spray drift potential across tested nozzle type and to compare the droplet size results of each nozzle by tank mix against the drift potential of each nozzle. RESULTS: The nozzle type affected the drift potential the most, but the spray solution also affected drift potential. The fine spray quality (TCP) resulted in the greatest drift potential (7.2%), whereas the coarse spray quality (AIXR) resulted in the lowest (1.3%), across all spray solutions. The spray solutions mixed at the 100 L ha(-1) application volume rate resulted in a higher drift potential than the same products mixed at the 50 L ha(-1) mix rate. The addition of the paraffinic DRT oil was significant in reducing the drift potential of Bacillus thuringiensis var. kurstkai (Bt)-only treatments across all tested nozzle types. The reduction in drift potential from the fine spray quality to the coarse spray quality was up to 85%. CONCLUSION: The addition of a DRT oil is an effective way to reduce the spray solution drift potential across all nozzle types and tank mixes evaluated in this study. The greatest reduction in drift potential can be achieved by changing nozzle type, which can reduce the losses of the spray to the surrounding environment. Venturi nozzles greatly reduce the drift potential compared with standard nozzles by as much as 85% across all three insecticide spray solutions. Results suggest that a significant reduction in drift potential can be achieved by changing the nozzle type, and can be achieved without a loss in control of DBM. © 2016 Society of Chemical Industry.

Retention and efficacy of ultra-low volume pesticide applications on Culex quinquefasciatus (Diptera: Culicidae).

To combat mosquitoes and the public health hazards they present, spraying chemical adulticides is an efficient and timely control method for immediate reduction of adult populations. With the growing consciousness of environmental and public health concerns, effective mosquito control means not only maximizing the effectiveness (in terms of mosquito mortality rates) of the pesticide application, but also minimizing the unintended effects (health hazard and environmental pollution). A series of experiments was carried out to assess the efficacy and deposition of ultra-low volume (ULV) sprays on adult mosquitoes which included the influence of chemical type, spray volume, spray concentration, droplet size, and deposit location (where the droplets land on the mosquito). A modified Potter Tower was used to apply an extremely fine spray (volume median diameter ∼20 µm) on caged adult mosquitoes (Culex quinquefasciatus). Reslin (50 g/L bioresmethrin) was diluted in either water or D-C-Tron plus spray oil (782 g/L paraffinic petroleum oil), Twilight (89 g/L phenothrin) was diluted in D-C-Tron, and the mosquito mortality was assessed 24 h after spraying. A fluorescent tracer was added to the spray mixture to determine the amount of spray on mosquitoes. A fluorescent microscope was also used to view the deposit of droplets on mosquitoes. It was found that droplet retention and mortality were reduced with the larger droplet sizes. Large water-based droplets tend to bounce off adult mosquitoes. There is a tendency for droplets approximately 20 µm in size to be retained on the fine hairs on the mosquito. The largest spray deposit was found on the adult mosquito wings and the lowest deposit on the head. Mortality was higher for formulations diluted with oil compared to those diluted with water. ULV applications with ultra-fine sprays (VMD 20 µm) and oil-based products resulted in maximum target efficacy under laboratory conditions, at minimum cost, and with the minimum amount of chemical adulticides.

Surface reconstruction of wheat leaf morphology from three-dimensional scanned data.

Realistic virtual models of leaf surfaces are important for several applications in the plant sciences, such as modelling agrichemical spray droplet movement and spreading on the surface. In this context, the virtual surfaces are required to be smooth enough to facilitate the use of the mathematical equations that govern the motion of the droplet. Although an effective approach is to apply discrete smoothing D2-spline algorithms to reconstruct the leaf surfaces from three-dimensional scanned data, difficulties arise when dealing with wheat (Triticum aestivum L.) leaves, which tend to twist and bend. To overcome this topological difficulty, we develop a parameterisation technique that rotates and translates the original data, allowing the surface to be fitted using the discrete smoothing D2-spline methods in the new parameter space. Our algorithm uses finite element methods to represent the surface as a linear combination of compactly supported shape functions. Numerical results confirm that the parameterisation, along with the use of discrete smoothing D2-spline techniques, produces realistic virtual representations of wheat leaves.