Bradley K. Fritz

Development of a Spray System for an Unmanned Aerial Vehicle Platform

Application of crop production and protection materials is a crucial component in the high productivity of American agriculture. Agricultural chemical application is frequently needed at specific times and locations for accurate site-specific management of crop pests. Piloted agricultural aircraft are typically used to treat large, unobstructed, continuous acreage crops and are not as efficient when working over small or obstructed plots. An Unmanned Aerial Vehicle (UAV), which can be remotely controlled or fly autonomously based on pre-programmed flight plans, may be used to make timely and efficient applications over these small area plots. This research developed a low volume spray system for use on a fully autonomous UAV to apply crop protection products on specified crop areas. This article discusses the development of the spray system and its integration with the flight control system of a fully autonomous, unmanned vertical take-off and landing helicopter. Sprayer actuation can be triggered by preset positional coordinates as monitored by the equipped Global Positioning System (GPS). The developed spray system has the potential to provide accurate, site-specific crop management when coupled with UAV systems. It also has great potential for vector control in the areas that are not easily accessible by personnel or equipment.

AERIAL APPLICATION METHODS FOR INCREASING SPRAY DEPOSITION ON WHEAT HEADS

Fusarium head blight (FHB) is a major disease of wheat and barley in several small grain production areas in the United States and, as such, the development and evaluation of aerial application technologies that enhance the spray deposition of fungicides, is critical to its management. This research was initiated to assess aerial spray technologies in an effort to increase spray deposits on wheat heads. Conventional hydraulic nozzles at two spray rates and two droplet sizes along with rotary atomizer and electrostatic treatments were investigated. Based on results from collectors and visual analysis the optimal spray treatment for deposition on wheat heads was hydraulic nozzles at 18.7 L/ha and a 350-m droplet volume mean diameter. The results from this study provide guidance for aerial fungicide applications for increased deposition on wheat heads.

Spray Drift Mitigation with Spray Mix Adjuvants

Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Four new drift control adjuvants were selected for drift studies in aerial applications. Deposition, downwind drift, and droplet spectra characteristics in a cotton canopy were collected on water sensitive paper (WSP) and mylar cards for measurement and analysis. The deposition, droplet size, droplet coverage, and total drops were highly correlated to the drift distance and treatments or adjuvants. Deposition on the monofilament lines generally decreased as sampling height increased for each treatment. The results will aid aerial applicators in selecting drift reduction agents to meet the drift mitigation criterion for a given application.

An Airborne Multispectral Imaging System Based on Two Consumer-Grade Cameras for Agricultural Remote Sensing

This paper describes the design and evaluation of an airborne multispectral imaging system based on two identical consumer-grade cameras for agricultural remote sensing. The cameras are equipped with a full-frame complementary metal oxide semiconductor (CMOS) sensor with 5616 × 3744 pixels. One camera captures normal color images, while the other is modified to obtain near-infrared (NIR) images. The color camera is also equipped with a GPS receiver to allow geotagged images. A remote control is used to trigger both cameras simultaneously. Images are stored in 14-bit RAW and 8-bit JPEG files in CompactFlash cards. The second-order transformation was used to align the color and NIR images to achieve subpixel alignment in four-band images. The imaging system was tested under various flight and land cover conditions and optimal camera settings were determined for airborne image acquisition. Images were captured at altitudes of 305–3050 m (1000–10,000 ft) and pixel sizes of 0.1–1.0 m were achieved. Four practical application examples are presented to illustrate how the imaging system was used to estimate cotton canopy cover, detect cotton root rot, and map henbit and giant reed infestations. Preliminary analysis of example images has shown that this system has potential for crop condition assessment, pest detection, and other agricultural applications.

Evaluation of Spray Drift Using Low-Speed Wind Tunnel Measurements and Dispersion Modeling

The EPAs proposed test plan for the validation testing of pesticide spray drift reduction technologies DRTs for row and field crops, focusing on the evaluation of ground application systems using the low-speed wind tunnel measurements and dispersion modeling, was evaluated. Relative drift reduction potential for a given DRT tested in a low-speed wind tunnel is derived from airborne droplet size measure- ments and airborne and deposited liquid volume measurements downwind from the spray nozzle. Mea- surements of droplet size and deposition data were made in a low-speed wind tunnel using standard reference nozzles. A blank emulsifiable concentration spray was applied at two different wind speeds. The wind tunnel dispersion WTDISP model was used to evaluate the drift potentials of each spray using the droplet size and spray flux measured in the wind tunnel. The specific objectives were 1 the evaluation of model accuracy by comparison of modeled downwind deposition to that measured in the wind tunnel, 2 the evaluation of drift reduction potential of the spray nozzles relative to a reference nozzle, and 3 the determination of low-speed wind tunnel data collection requirements for model input to optimize the evalu- ation process. The modeled deposition data did not compare well to the measured deposition data, but this was expected as the model was not meant to be used for this purpose. The tested nozzles were rated using the International Standards Organization drift classification standard. The drift ratings generally showed trends of larger droplet producing nozzles having greater drift reduction ratings. An examination of several scenarios using reduced model input requirements, which would decrease the low-speed wind tunnel data collection time, did not show any conclusive results. They suggest that further testing and refinement of the data collection process and the WTDISP model may support wider use of this system for the assessment of DRTs.

Characterization of Truck-Mounted Atomization Equipment Typically Used in Vector Control

ABSTRACT The control of medically important arthropod vectors of human and animal disease is a high priority for both public health and military officials. Because droplet size of pesticide spray material is a critical factor affecting vector control applications, the droplet-size spectra produced by 11 sprayers and 3 spray formulations were evaluated. Droplet-size spectra were measured by a laser diffraction instrument, a hot-wire system, and rotating slides. There were considerable differences in the droplet-size spectra produced by the different sprayers tested. The volume median diameter (DV0.5) for the water-based sprays ranged from 4.7 to 211 µm, depending on the sprayer, and the percent of spray volume contained in droplets less than 20 µm (%vol <20 µm) ranged between 0.5% and 98.9%. The DV0.5 measurements for the oil-based sprays ranged from 9.4 to 125.3 µm and the %vol <20 µm ranged between 2.4% and 97.9%. The correlations between the DV0.5 measured by the laser system (DV0.5-laser) and the mass median diameter, Sauter diameter, and DV0.5 measured by the AIMS probe were all significant. Generally, the slide DV0.5s were numerically similar to the DV0.5 from the laser system and the Sauter diameter from the Army Insecticide Measuring System probe. There was less consistent agreement between the % <32 µm values obtained from the slides and those from the other 2 samplers. The information presented can be used by applicators to select the sprayer that produces the droplet-size spectra needed for their particular application situation.

Effects of Wind Speed on Aerosol Spray Penetration in Adult Mosquito Bioassay Cages

ABSTRACT Bioassay cages are commonly used to assess efficacy of insecticides against adult mosquitoes in the field. To correlate adult mortality readings to insecticidal efficacy and/or spray application parameters properly, it is important to know how the cage used in the bioassay interacts with the spray cloud containing the applied insecticide. This study compared the size of droplets, wind speed, and amount of spray material penetrating cages and outside of cages in a wind tunnel at different wind speeds. Two bioassay cages, Center for Medical, Agricultural and Veterinary Entomology (CMAVE) and Circle, were evaluated. The screen materials used on these cages reduced the size of droplets, wind speed, and amount of spray material inside the cages as compared to the spray cloud and wind velocity outside of the cages. When the wind speed in the dispersion tunnel was set at 0.6 m/sec (1.3 mph), the mean wind speed inside of the CMAVE Bioassay Cage and Circle Cage was 0.045 m/sec (0.10 mph) and 0.075 m/sec (0.17 mph), respectively. At air velocities of 2.2 m/sec (4.9 mph) in the dispersion tunnel, the mean wind speed inside of the CMAVE Bioassay Cage and Circle Cage was 0.83 m/sec (1.86 mph) and 0.71 m/sec (1.59 mph), respectively. Consequently, there was a consistent 50–70% reduction of spray material penetrating the cages compared to the spray cloud that approached the cages. These results provide a better understanding of the impact of wind speed, cage design, and construction on ultra-low-volume spray droplets.

Spray Characterization of Ultra-Low-Volume Sprayers Typically Used in Vector Control

Abstract Numerous spray machines are used to apply pesticides for the control of human disease vectors, such as mosquitoes and flies, and the selection and setup of these machines significantly affects the level of control achieved during an application. The droplet spectra produced by 9 different ultra-low–volume sprayers with oil- and water-based spray solutions were evaluated along with 2 thermal foggers with the use of diesel-based spray solutions. The droplet spectra from the sprayers were measured with the use of laser diffraction droplet sizing equipment. The volume median diameter from the sprayers ranged from 14.8 to 61.9 µm for the oil-based spray solutions and 15.5 to 87.5 µm for the water-based spray solutions. The 2 thermal foggers generated sprays with a volume median diameter of 3.5 µm. The data presented will allow spray applicators to select the spray solution and sprayer that generate the droplet-size spectra that meet the desired specific spray application scenarios.

AEROSOL SAMPLING: COMPARISON OF TWO ROTATING IMPACTORS FOR FIELD DROPLET SIZING AND VOLUMETRIC MEASUREMENTS

Abstract This article compares the collection characteristics of a new rotating impactor Florida Latham Bonds (FLB) sampler for ultrafine aerosols with a mimic of the industry standard (Hock-type). The volume and droplet-size distribution collected by the rotating impactors were measured via spectroscopy and microscopy. The rotary impactors were colocated with an isokinetic air sampler for a total volume flux measurement and a laser diffraction instrument for droplet-size distribution measurement. The measured volumetric flux and droplet-size distribution collection efficiencies were compared across 3 wind speeds (1, 1.8, and 3.5 m/sec). The FLB sampler had higher flux collection efficiencies than the Hock-type sampler. The FLB sampler collected 89%, 87%, and 98% of the total volume available per unit area at 1, 1.8, and 3.5 m/sec, respectively, whereas the Hock-type sampler collected 68%, 19%, and 21% of across the same wind speeds. Changes in wind speed had less impact and resulted in less data variability for the FLB sampler.

Spray Characterization of Thermal Fogging Equipment Typically Used in Vector Control

ABSTRACT Droplet size spectra from different sprayers used to generate insecticide-laden fogs for controlling flying insects were measured by a laser diffraction instrument and Teflon-coated slides. The objectives of this work were to present not only information on spray-system droplet size generated by different sprayers, but to compare methodologies by which other similar systems can be evaluated and give applicators sprayer-system performance data. Data from 45 replicated spray tests, comprising 11 sprayers and 5 pesticides, showed a wide range in the droplet size spectra produced. The volume median diameter measurements ranged from 2.6 to 75.5 μm for diesel-diluted sprays and from 27.9 to 59.9 μm for water-diluted sprays. Similarly, the percent volume <20 μm ranged between 12.0–100% and 8.5–30.7%, for diesel- and water-diluted sprays, respectively. The droplet sizes measured by the swinging slide and laser diffraction methods were not consistent. The information presented aids users in sprayer selection and operation to produce the specific droplet size spectra required for a particular application.