Location: Application Technology Research2022 Annual Report
The long-term objective of this research is to advance spray applications with coordinated intelligent-decision technologies and strategies that enhance pesticide application efficiency and environmental stewardship for efficacious and affordable control of pest insects, diseases and weeds. Objective 1: Develop intelligent precision technologies to efficiently apply pesticides and bio-products for efficacious and sustainable control of pest insects and arthropods, diseases and weeds to protect horticultural, field and greenhouse crops. Sub-objective 1.1: Develop a reliable and user-friendly intelligent spray-decision system as a retrofit for new and existing air-assisted sprayers to deliver pesticides and bio-products accurately, economically, and environmentally for field specialty crops. Sub-objective 1.2: Develop greenhouse intelligent spray systems for real-time control of individual nozzle outputs to improve spray deposition quality and reduce waste of water and chemicals. Objective 2: Develop coordinated application methodologies to reduce pesticide use, reduce crop protection costs, reduce chemical contaminations to the environment, and protect workers, livestock, natural resources and sensitive ecosystems. Sub-objective 2.1: Improve spray droplet fading process to maximize coverage area after deposition on plants through coordinating spray parameters including droplet size, formulation physical properties, plant surface morphology, and ambient air conditions. Sub-objective 2.2: Improve spray droplet retention and reduce runoff on plants through coordinating the influences of droplet size and velocity, travel speed, spray formulation physical properties, crop leaf surface morphology, and leaf surface orientation on dynamic impact, retention, rebound and spread process of spray droplets on plants.
A versatile intelligent spray control system and mounting kits will be developed as a retrofit to different types of tractor-driven sprayers to deliver pesticides and bio-products for different specialty crops. A microprocessor controlled premixing inline injection module will be developed and integrated into the versatile spray control system. Performance of these sprayers will be tested for their accuracy to manipulate spray deposition, spray drift, off-target loss and spray volume consumption in comparison with conventional sprayers. Efficacy tests will be conducted in nurseries, apple orchards and vineyards to compare pest control, pesticide quantity used, and cost savings for the sprayers with and without intelligent functions. Spray drift models will be developed to predict movement of droplets discharged from conventional and intelligent sprayers under nursery, orchard and vineyard conditions. Greenhouse intelligent spray systems will be developed for real-time control of individual nozzle outputs to improve spray deposition quality and reduce waste of water and chemicals. The automatic greenhouse spray system will be a retrofit attached to existing watering booms. Laboratory tests will be conducted to validate the spray control system accuracies in spray delay time, nozzle activation and spray volume using artificial objects of different regular geometric shapes and surface textures, and artificial plants of different canopy structures. Spray deposition and pest control efficacy tests in greenhouses will then be conducted to validate the intelligent spray control system. Microscopic spray droplet spreading times and areas on leaves will be investigated to maximize and stabilize coverage area after deposition on plants. Investigation parameters include droplet size, formulation physical properties, plant surface morphology, and ambient air conditions. Droplet fading rate, absorption rate and residual pattern coverage area will be measured on the waxy, semi-waxy and hairy leaf surfaces, and hydrophilic and hydrophobic glass slide surfaces. Field experiments will be conducted in ornamental nurseries, orchards, greenhouses, vegetables, traditional crops and weeds to verify laboratory discoveries effects of the most influenced factors on droplet spreading areas. Dynamic effects of spray parameters on the droplet impact, rebound, retention, adhesion, and spread process on plants will be determined. The parameters are droplet size and velocity, travel speed, spray formulation type, and leaf surface morphology and orientation. Significance of coordinating these parameters to improve spray droplet retention and reduce runoff on plants will be analyzed. Dynamic impact of water-based droplets on plant leaves will also be investigated in a wind tunnel under controlled conditions.
To achieve Objective 1.1, following progress was made: 1) A commercial stereo vision was tested as a means of detecting the canopy of ornamental and tree crops. A custom-designed graphic user interface was developed to control the depth camera and to acquire color and infrared images and depth data to a local computer. The stereo vision was evaluated in a temperature-controlled room with and without illumination to simulate a wide range of field conditions. Although its measurements could be influenced by the temperature and illumination, their relative errors were less than 1% and the maximum variation between the average measurements was 14 mm. The stereo vision was able to detect 31% to 72% area of a 20-mm wide target and 72% to 89% area of 40 mm wide target. The stereo vision showed acceptable performance in detecting canopy contour changes with measurement errors of 2.8% to 15.3% while detecting the distances to outdoor crabapple and oak trees under sunny condition. In addition, the stereo vision detected canopy in various outdoor illuminations from sunrise to sunset with accuracy of less than 10% relative error. The stereo vision had less than 6% variations in detecting crabapple canopy under various illumination levels between sunrise and sunset in terms of the measurement stability. 2) A variable rate spray controller using a stereo vision was developed and evaluated with moving spray targets at travel speeds from 3.2 to 8.0 km/h under laboratory conditions. The stereo vision from the controller detected the target at the frame rate of 5 Hz and modulated spray nozzles at 10 Hz. A customized graphical user interface was developed to operate the controller, display incoming data and control other components. Evaluations of the controller with a flat, 3-dimensional box column, and artificial tree targets at the travel speeds from 3.2 to 8.0 km/h showed that the controller consistently activated the nozzles a fraction of a second before the target arrived on the spray axis and repeatedly detected the volume of the spray target with variation less than 12% for the same target at one travel speed. The evaluation results also showed the volume measurements of the controller were generally higher than manually calculated volume as much as 33% which resulted from duplicated target detection between detection cycles of the controller. These duplicated detections resulted in over applications as much as 38% although the controller repeatedly discharged spray volumes with variation less than 11% for the same target at same travel speed. On average, the controller was able to manage variable rate spray applications for the travel speeds from 3.2 to 8.0 km/h. 3) Two different Pulse width modulation (PWM) spray systems were integrated in a reference air-blast sprayer for comparisons of foliar spray deposition quantity and potential reduction in off-target losses in orchards with young trees. The two systems were a manual PWM-controlled constant-rate system and a laser-guided PWM-controlled variable-rate system. The same laser-guided spray system was also used with deactivating PWM valves to produce a conventional constant-rate application as a reference for the tests. The PWM technology improved application efficiency to treat two or more rows of trees with a single spray pass, and also reduced variation in the relationship between foliar deposition and spray drift loss. 4) Comprehensive understanding of spray parameters was established for the hollow-cone nozzles manipulated with PWM solenoid valves to produce droplets with variable flow rates. The spray parameters included nozzle flowrates, upstream and downstream pressures on the PWM valves, nozzle activation pressures and times, and droplet size distributions discharged from the nozzles. Test variables included five disc-core hollow-cone nozzle capacities, two 10-Hz PWM valve designs, five operating pressures, and ten duty cycles ranging from 10% to 100%. Test results illustrated that these parameters were greatly affected by the operating pressure, nozzle disc orifice size, PWM duty cycle and solenoid valve design. In general, nozzles with larger disc orifice and higher operating pressures resulted in higher flowrates as expected, whilst the nozzle activation pressure decreased as the duty cycle decreased. Higher operating pressures and larger nozzles generated droplets with more consistent size distributions across duty cycles from 10% to 100%. For droplets smaller than 100 µm, the spray volume fraction remained relatively consistent or slightly decreased as duty cycle increased but increased as the pressure increased. In comparison, the spray volume fraction increased as both duty cycle and operating pressure increased for droplets between 100 and 300 µm and decreased for the portion of droplets greater than 300 µm. To achieve Objective 1.2, following progress was made: 1) Droplet size distributions, activation pressures acting on nozzle orifices, and flow rates discharged from nozzles were investigated for test combinations of ten PWM duty cycles, six flat-fan nozzles with different orifice sizes, and two PWM solenoid valve designs. Test results showed that the droplet size distribution, activation pressure, and flow rate varied with the duty cycle, nozzle orifice size, and PWM solenoid valve designs influenced droplet size distribution, activation pressure and flow rate. For small orifice size nozzles, droplet sizes did not vary significantly with all duty cycles from 10% to 100%. To obtain relatively consistent droplet size distributions, medium size nozzles required PWM duty cycles to be at least 20% while large nozzles required duty cycles to be 30% or greater. The same nozzles coupled with PWM solenoid valves from two different designs discharged different flow rates for the same duty cycles in the range of 10% and 90%. 2) An offline variable-rate spraying system using a laser scanning sensor was developed for greenhouse spray applications. A convex hull method was used to improve the plant canopy volume estimation for calculating and controlling spray rates for individual plants. The spray system was tested for its spray coverage performance in a greenhouse environment against the conventional constant-rate spray system. The offline variable-rate system significantly reduced spray coverage at the edges of plant canopies while meeting the recommended spray coverage percentages. To achieve Objective 2.1, following progress was made: Droplets containing three different adjuvants deposited on waxy weed leaves were investigated inside an environmental control chamber. Droplet dispersion and fading process on different weed leaves were characterized with 300 and 600 µm herbicidal droplets. A 3D optical surface profiler and the areal roughness parameter for roughness height were used to quantify surface roughness for different leaf types ranging in wettability from very easy to very difficult to wet (contact angles between 35 and 160 degree) and roughness from smooth to very rough. To achieve Objective 2.2, following progress was made: Droplet impact, rebound and retention on different waxy leaves were investigated. Spray solutions were composed of distilled water and adjuvant concentrations of 0.0, 0.10, 0.25, 0.50, 0.75, and 1.00% (v/v). The adjuvants tested were a crop oil concentrate, a methylated seed oil, a nonionic surfactant, an oil-nonionic silicone surfactant blend, and organosilicone. Spray droplets were emitted from a streamed monosized droplet generator mounted on a horizontal motion track traveling at a speed of 1.34 m/s. Droplet motion and impacts were recorded with three ultrahigh-speed video cameras and analyzed using 3D motion analysis software. Deposition was determined by comparing droplet volume before and after impact. Complete deposition was achieved for all adjuvant classes on smooth-easy to wet leaves at all concentrations, whereas deposition on rough-hard to wet leaves increased linearly as concentrations increased. On the rough-hard to wet leaves, approximately 70% deposition was achieved for the nonionic and silicone adjuvants at 0.75% and 0.50% concentrations, respectively. Depositions of less than 70% were achieved for the crop oil concentrate, methylated seed oil, and oil-silicone adjuvants.
1. Greenhouse intelligent spray control system to deliver the right amount of spray to the right target. Precision variable-rate spraying technology to deliver pesticides, irrigation, nutrients and other foliar applied products is lacking in greenhouse crop production. During the short growing period, it is very common that small young plants are over sprayed, large plants are under sprayed, and empty areas are unnecessarily sprayed, causing significant waste of sprayed products and environment contamination. ARS scientists at Wooster, Ohio, developed an experimental laser-guided precision spraying system to minimize these problems. The system was designed as a retrofit attachment onto the existing horizontal booms to automatically control spray outputs to match greenhouse crop presence and canopy architectures in real time. Test results showed that this precision variable-rate system greatly increased the delivery accuracy of sprayed product and was able to reduce spray volume by 29% to 51% compared with the conventional constant-rate spray applications. As a result, transferring the technology to an automation company for commercialization was established. Greenhouse growers are anticipated to use this environmentally-responsible technology in the near future to efficiently grow high-quality crops with significant savings of chemicals, water and nutrients.
2. Electronic nose system to diagnose whitefly and aphid infested tomato plants. Tomatoes are subject to attack by insect pests especially whiteflies and aphids from the time of first emergence as seedlings until harvest. Technologies to early detect these insects are needed for better treatments. An experimental electronic nose (E-nose) system equipped with a gas sensor array and real-time control panel was developed by ARS scientists at Wooster, Ohio, with their collaborators at The Ohio State University. The E-nose system was designed to diagnose infestations of tomato plants by whiteflies and aphids based on an optimized sensor array. To inform detection, amounts of volatile organic compounds emitted from greenhouse-grown tomato plants with and without infestation of whiteflies and aphids were determined. An interface computer program was developed to analyze the release of volatile organic compounds for fast diagnoses. GC-MS analysis confirmed the diagnosis of the developed E-nose system and demonstrated its ability as a potential non-destructive and portable tool. Even though further validation is needed for the E-nose system sensitivity, reliability and repeatability in large greenhouses, this new system provides new opportunities for growers and researchers to accurately diagnose infested plants at early stages and thus establish a smart platform for the insect control and pest management to grow healthy crops.
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