Research Project: Improved Pest Control Application Technologies for Sustainable Crop Protection

Location: Application Technology Research

2019 Annual Report

Objectives
Objective 1: Establish comprehensive ground-based strategies to increase foliar retention of pesticide spray for traditional and specialty crops produced in greenhouses and the field. Sub-objective 1.1: Determine the influence of spray parameters including droplet size, formulation physical properties, ambient air conditions, and plant surface morphology on the droplet behavior, evaporation, absorption, and residual pattern on plant surfaces. Sub-objective 1.2: Determine the influence of droplet size and velocity, travel speed, spray formulation physical properties, crop characteristics, leaf surface morphology, and leaf surface orientation on spray droplet dynamic impact, retention, rebound and coverage. Objective 2: Develop intelligent-decision spraying systems to increase spray application efficiency and reduce off-target losses. Sub-objective 2.1: Develop advanced sensor-based intelligent decision systems that can be adapted for different types of sprayers. Sub-objective 2.2: Investigate spray deposition uniformity, off-target losses and pesticide savings with intelligent-decision controlled sprayers. Sub-objective 2.3: Develop drift reduction technologies (DRT) with intelligent decision systems to aid in reducing off-target losses and enabling development of sustainable production programs. Objective 3: Develop ground-based methods for improving delivery of weed management materials to nursery containerized production systems. Sub-objective 3.1: Optimize application factors such as droplet size, spray volume and irrigation volume to improve delivery efficiency of herbicides through a nursery crop canopy to the substrate surface. Sub-objective 3.2: Determine the influence of delivery and plant parameters such as air-assistance, travel speed, irrigation volume, and canopy structure on deposition of granular materials on container substrates. Objective 4: Develop alternative delivery methods for agrochemicals and bioproducts. Sub-objective 4.1: Develop mechanical delivery devices to apply entomopathogenic nematodes. Sub-objective 4.2: Develop methods and strategies for efficiently applying pheromones.

Approach
This project envisions that research on intelligent spray technologies, efficient applications of bio-products as alternative pesticides, and coordinated strategies can enhance pesticide application efficiency for efficacious and affordable control of insects, diseases and weeds. The research will focus on delivery systems in conjunction with spray droplet transport, fate of spray droplets upon target impact, epidemiology of pests and pathogens, pesticide formulation, and microclimatic conditions. Selective approaches to achieve the objectives will be to: (1) establish comprehensive ground-based strategies to increase pesticide retention on specialty and traditional crops in greenhouse and field environments; determine the influence of spray parameters such as droplet size, formulation physical properties, ambient air conditions, and plant surface morphology on the droplet impaction, rebound, retention, spread, evaporation, absorption, and residual pattern on plant surfaces under the conditions that individual parameters can be controlled separately; (2) innovate advanced intelligent-decision spraying systems to increase spray application efficiency; investigate spray deposition uniformity, spray drift, offtarget losses and pesticide savings for ornamental nurseries, orchards and other specialty crops with intelligent-decision controlled sprayers; develop drift reduction technologies with intelligent decision systems to aid in enabling development of sustainable production programs; (3) develop methodologies to improve herbicide applications for containerized nursery production systems; optimize application factors such as droplet size, spray volume and irrigation volume to improve delivery efficiency of herbicides through a nursery crop canopy to the substrate surface; determine the influence of delivery and plant parameters such as air-assistance, travel speed, irrigation volume, and canopy structure on deposition of granular herbicides on container substrates; (4) develop mechanical delivery devices to apply new agrochemicals and bio-products for pest control; discover innovative techniques for accurate delivery of entomopathogenic nematode infected insect larvae to effectively control soil pests; develop methods and strategies for efficiently applying pheromones by designing new dispensers with controlled evaporation rates.

Progress Report
A universal intelligent spray control system was developed as a retrofit kit mounted on different types of conventional air-assisted sprayers. The control system was tested with eleven growers’ sprayers in nurseries, fruit and nut orchards, and vineyards in Ohio, Oregon, Tennessee, South Carolina, Texas, California and Australia. With the retrofit, these conventional sprayers were upgraded to perform intelligent functions in controlling spray outputs to match canopy presence, size and leaf density in real time. These on-farm tests included evaluations of their pest control effectiveness, spray application efficiency, chemical savings and operation reliability. Numerous demonstrations of the new spray technology were presented in workshops, trade shows and other educational programs. Field tests were conducted in a nursery, an apple orchard and a vineyard to evaluate spray deposition quality and off-target loss discharged from two air-assisted sprayers retrofitted with a newly developed laser-guided intelligent spray control system. The sprayers were used under two different spray operational modes for comparisons: automatic variable rate mode representing the new spray technology, and conventional constant rate mode representing the conventional spraying practice. Targets were placed at different locations inside canopies, on the ground and in the air to measure foliar spray deposition and off-target losses. Tests followed identical procedures at three different growth stages. Comparative experiments of intelligent variable-rate and conventional constant-rate spray applications for pesticide use and pest control were conducted at a fruit farm in Ohio. Apple, peach, blueberry and raspberry were used as host plants. Pest severity of codling moth, oriental fruit moth, scab and powdery mildew in apple trees, oriental fruit moth, brown rot and powdery mildew in peach trees, spotted wing drosophila, mummy berry and phomopsis in blueberry and anthracnose in black raspberry, were assessed. Efficacy tests for two different grower sprayers retrofitted with the laser-guided intelligent spray control system to control pests were conducted at two different commercial nurseries in Ohio. The same sprayers with conventional constant-rate mode were also used for comparison. Crabapple, apple, red maple, birch, sycamore and dogwood were used as the host plants. Insect and disease control effectiveness and chemical savings were documented. An experimental automatic premixing in-line injection system was improved to reduce the tank mixture leftover problem associated with variable-rate orchard sprayers. This system primarily consisted of a precision fluid metering pump, a water pump, a static mixer, a premixing tank and a buffer tank. Accuracy of the metering pump was tested with simulated pesticides (tap water, turpentine oil, prime oil, and four concentrations of sucrose solutions) with various viscosities. Test results were analyzed for the mixture concentration uniformity and for relative errors between measured and desired volumes for the system. Water droplet impact and adhesion on leaves were investigated with various levels of leaf surface roughness or leaf wettability. An optical profiler and three industry standard roughness parameters: height, skewness, and kurtosis, were used to quantify the surface roughness for different leaf types ranging in wettability from very easy to very difficult. These parameters were then compared and related to the adhesion and spreading of impacting water droplets at different surfactant concentrations and impact velocities. Droplet size and impact velocity were controlled by a streamed mono-sized droplet generator mounted on a horizontal motion track. Droplet motion and impacts were recorded with three ultrahigh-speed video cameras and analyzed using 3D motion analysis software. A 3D ultrahigh-speed video surveillance system was used to monitor the effects of hairy trichomes on the adhesion, spread, and rebound of impacting water droplets on plant leaves. The effects were determined by comparing the droplet impact behavior for different surfactant concentrations on maize, soy, and squash leaves when their trichomes were present and then removed. Trichomes were removed mechanically with an electric razor. Potential changes to the surface characteristics of the leaves due to trichome removal were monitored by measuring the wax load, surface roughness, wettability and SEM micrographs before and after trichome removal. Droplet size and impact velocity were controlled by a streamed mono-sized droplet generator mounted on a horizontal motion track, with constant track speeds. Droplet motion was analyzed using 3D motion analysis software. An electronic nose (E-nose) system equipped with a set of sensitive sensor array was investigated for a fast diagnosis of aphid infestation at early stages of tomato plants. The system was preliminarily tested for its capability to distinguish volatile organic compounds released from heathy plants and from aphids-stressed tomato plants at the beginning of infestation under greenhouse conditions. A gas chromatography–mass spectrometry instrument was used to verify the analyses of volatile compounds identified with the E-nose. Preliminary results illustrated that tomato plants infested by aphids released new volatile compounds for combating aphid attacks. These new compounds could be used as the bio-markers for the E-nose to identify infested plants. However, further investigations are needed to quantify the new volatile compounds released from different varieties under different growth conditions to validate the E-nose sensitivity and reliability. Droplet size distributions of rotary micro sprinkler nozzles with five different orifice diameters were investigated for pesticide applications to minimize spray drift in orchard systems. A particle-droplet laser image analysis system was used to measure droplet spectrum at two pressures and two radial distances from the nozzle center. Nozzle orifice sizes, rotation speeds and flow rates were also measured. Droplet sizes varied with the nozzle tip orifice size, operating pressure and sampling location. Spiral-shaped spray patterns formed due to the spinning discharge port, within which droplet densities varied with location, nozzle diameter and operating pressure. A multiple variable regression model was developed to predict volume median diameters of droplets. discharged from the sprinkler spinning nozzles. The accuracy of an inexpensive indoor-use radial laser sensor and a sophisticated algorithm were evaluated in detecting surface edge profiles of plants before their integration into the intelligent spray system development for greenhouse applications. Evaluations included four objects of different regular geometrical shapes and surface textures, and two artificial plants of different canopy structures. Three-dimensional images for the object surfaces were reconstructed with the data acquired from the laser sensor at four different detection heights above each object, five sensor travel speeds, and 15 horizontal distances to the sensor. Edge profiles of the six objects detected with the laser sensor were compared with images taken with a digital camera. The edge similarity score was used to define the differences in surface edge profiles between images obtained from the laser sensor and the camera. Consequentially, a preliminary intelligent spray system was designed for real-time control of individual nozzle outputs for greenhouse applications. The system mainly consisted of the laser scanning sensor, 12 individual variable-rate nozzles, an embedded computer, a spray control unit, and a 3.6 m long mobile spray boom. Each nozzle was coupled with a pulse width modulated solenoid valve to discharge variable rates based on object presence and plant canopy structures. Laboratory tests were conducted to evaluate the intelligent spray control system accuracy in terms of the spray delay time, nozzle activation, and spray volume using the four different regular-shaped objects and two artificial plants. Other experimental variables included three laser detection heights from 0.5 to 1.0 m and five constant travel speeds from 1.6 to 4.8 km/h. A high-speed video camera was used to determine delay time and nozzle activation in discharging sprays on target objects. After the laboratory tests, this experimental laser-guided spray system was implemented into a water-boom system in a commercial greenhouse for future investigations in its accuracy for discharging variable-rate sprays to save pesticides, water, and nutrients.

Accomplishments
1. Universal intelligent spray control system as a retrofitted intelligent variable-rate sprayers. Conventional constant-rate sprayers often use excessive amounts of pesticide to achieve insect and disease control in ornamental nurseries. USDA scientists from Wooster, Ohio, recently developed intelligent variable-rate spray technology that could be retrofitted on conventional sprayers to deliver pesticides to tree canopies precisely with minimum off-target loss to the ground and air, but there are few reports about the efficacy of these sprayers. To verify reliability of the new spray technology for effective pest control, they retrofitted two different commonly used conventional sprayers with the intelligent variable-rate spray system and compared their efficiency with conventional constant-rate spray applications in commercial ornamental nurseries. The intelligent spray applications reduced pesticide use by 52% and 56% on average while maintaining equally or more effective control of pest insects and diseases. The retrofitted intelligent sprayers proved to be a highly efficient and environmentally friendly pesticide application technology for the ornamental nursery industry.

2. Control of pest insects and diseases in ornamental nurseries with retrofitted intelligent variable-rate sprayers. Conventional constant-rate sprayers often use excessive amounts of pesticide to achieve insect and disease control in ornamental nurseries. Recently developed intelligent variable-rate spray technology can enable conventional sprayers to deliver pesticides to tree canopies precisely with minimum off-target loss to the ground and air. However, there are very few reports about the efficacy of these sprayers equipped with the new technology. USDA scientist from Wooster, Ohio, retrofitted two different commonly used conventional sprayers with the intelligent variable-rate spray system and compared their efficiency with conventional constant-rate spray applications. The intelligent spray applications reduced pesticide use by 52% and 56% on average at the two nurseries while maintaining equally or more effective control of pest insects and diseases. The retrofitted intelligent sprayers proved to be a highly efficient and environmentally friendly pesticide application technology for the ornamental nursery industry.

3. Retrofitted intelligent sprayers to control insects and diseases in fruit plants. Commercial fruit producers usually use constant-rate spray applicators to control pest insects and diseases. A multi-port air-assisted sprayer retrofitted with the intelligent variable-rate spray system was developed by USDA scientists from Wooster, Ohio to control spray outputs based on the presence, structure and foliage density of plants, and was tested for its efficacy in controlling insects and diseases in apple, peach, blueberry and raspberry plants in commercial fruit farms. Two-year on-farm field tests demonstrated that the intelligent variable-rate sprayer used 29% to 59% lower amounts of pesticides while maintaining equal or better insect and disease control than conventional constant rate sprayers. The efficacy in pest management coupled with significantly less pesticide use reduces production costs and improves production efficiency.

Review Publications
Silva, J.E., Zhu, H., Cunha, J. 2018. Spray outputs from a variable-rate sprayer manipulated with PWM solenoid valves. Applied Engineering in Agriculture. 34(3):527-534. https://doi.org/10.13031/aea.12556.
Xiao, L., Zhu, H., Wallhead, M.W., Horst, L., Ling, P., Krause, C.R. 2018. Characterization of biological pesticide deliveries through hydraulic nozzles. Transactions of the ASABE. 61(3):897-908. https://doi.org/10.13031/trans.12698.
Yan, T., Zhu, H., Sun, L., Wang, X., Ling, P. 2018. Detection of 3-D objects with a 2-D laser scanning sensor for greenhouse spray applications. Computers and Electronics in Agriculture. 152:363-374. https://doi.org/10.1016/j.compag.2018.07.030.
Sudduth, K.A., Franzen, A.J., Zhu, H., Drummond, S.T. 2018. Variable-rate application technologies in precision agriculture. In: Stafford, J.V., editor. Precision Agriculture for Sustainability. Cambridge, United Kingdom: Burleigh Dodds Science Publishing Limited. p. 171-194.
Yan, T., Wang, X., Zhu, H., Ling, P. 2019. Evaluation of object surface edge profiles detected with a 2-D laser scanning sensor. Sensors. 18(11):1-17. https://doi.org/10.3390/s18114060.
Hong, S., Zhao, L., Zhu, H. 2019. SAAS, a computer program for estimating pesticide spray efficiency and drift of air-assisted pesticide applications. Computers and Electronics in Agriculture. 155:58-68. https://doi.org/10.1016/j.compag.2018.09.031.
Zhang, Z., Zhu, H., Guler, H., Shen, Y. 2019. Improved premixing in-line injection system for variable-rate orchard sprayers with Arduino Platform. Computers and Electronics in Agriculture. 162:389-396. https://doi.org/10.1016/j.compag.2019.04.023.
Lin, J., Zhu, H. 2019. Fading process of herbicidal droplets amended with emulsifiable spray adjuvants on cucurbitaceae leaves. Transactions of the ASABE. 61(6):1881-1888. https://doi.org/10.13031/trans.13061.
You, K., Zhu, H., Abbott, J.R. 2019. Assessment of fluorescent dye Brilliant Sulfaflavine on stainless steel screens as spray collectors. Transactions of the ASABE. 62(2):495-503. https://doi.org/10.13031/trans.13136.