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ARS Home » Midwest Area » Wooster, Ohio » Application Technology Research » Research » Research Project #425625

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

Location: Application Technology Research

2015 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 bio-products. 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, off-target 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
Commercially available esterified seed oil surfactant and petroleum oil surfactant were evaluated to modify spread areas and fading times of water and herbicide droplets on watermelon leaves which were used to simulate paddy melon leaves. A combination of two systemic herbicides (triclopyr and glyphosate) was also used to form a water-based spray solution for comparisons. The formulation of glyphosate herbicide contained a non-ionic surfactant. Tests were conducted with 250 and 450 µm sessile droplets at 30% and 60% relative humidity inside a controlled environmental chamber. The sessile droplets were produced with a single-droplet generator. A controlled environmental system with 100% relative humidity was developed for direct measurements of foliar uptake rates of sessile water droplets at various locations on waxy leaf surfaces during two diurnal periods between 10:30 and 13:00 (noon) and between 16:00 and 19:00 (evening) at ambient temperatures of 15 and 20°C. Sessile droplets of 340 and 540 µm in diameter were produced with a single-droplet generator. Stomatal densities and osmotic pressures on leaves were also measured with a cold field emission scanning electronic microscope (CFESEM) and a vapor pressure osmometer, respectively. At 100% relative humidity inside the environmental chamber, droplets remained unchanged after they were deposited on a non-permeable glass but they penetrated leaf tissues after they were deposited on leaves. Dynamics of impact and spread of water droplets of 185 to 693 µm at 1.85 to 6.4 m s-1 impact speeds and 28 to 75° impact angles on two soybean leaf surface orientations (horizontal and 30° inclination) were investigated with two high-speed digital video cameras and a mono-sized droplet generator under laboratory-controlled conditions. Within the test ranges of the variables, droplet rebound was not observed after impact on leaf surfaces while droplets larger than 300 µm were observed to slide on the 30° inclined surface. Droplet spread factors increased with droplet diameters and impact speeds but decreased with impact angles. A system was constructed to precisely determine semiochemical release rates under environmentally-controlled conditions. Three dissimilar types of solid matrix, passive emission semiochemical dispensers were selected to verify the system capabilities. The rate of mass loss for each semiochemical was measured inside a 0.11 m3 air sealed reservoir. Each product was tested at five ambient temperatures and three values of relative humidity. Temperatures were maintained at their set points within ±1.0 °C and relative humidity within ±0.4%. A microprocessor controlled premixing inline injection system implementing a ceramic piston chemical metering pump and two small transition tanks was developed for air-assisted variable-rate sprayers. Unlike conventional direct inline injection systems that inject chemical concentrates into the delivery lines, this system first dispensed specific amounts of water and chemical concentrates into an injection chamber and then agitated the mixture in a transition (or premixing) tank. The mixture was then transferred into a second transition (or buffer) tank for the spray pump to discharge. This process was repeated when the buffer tank neared empty. The mixture in the buffer tank was maintained at a constant concentration that allowed the sprayer to discharge a wide dynamic range of variable-rate outputs with a consistent concentration for every nozzle. An embedded computer with a touch screen monitor allowed operators to interface with the injection system. The metering pump accuracy was verified with three simulated pesticides (water, prime oil, and milk). Mixture uniformity consistency was tested with five different viscous simulated pesticides (sucrose solutions) at viscosities ranging from 0.9 to 31.3 mPa·s. Field tests were conducted to compare spray deposition and coverage inside shade tree canopies, spray drift and ground loss between the intelligent and conventional air-blast sprayers at three different travel speeds.


Accomplishments
1. Embedded computer controlled premixing inline injection system for air-assisted variable-rate sprayers. Conventional sprayers in ornamental nurseries and orchards are grossly inefficient because the same amounts of chemicals are constantly discharged to the field regardless of plant presence, canopy structure, or leaf foliage density. A promising solution is the use of new variable-rate spray technologies developed by ARS researchers at Wooster, Ohio. However, the new spraying systems also encounter excessive tank mixture leftover problems. To overcome this challenge, ARS researchers at Wooster, Ohio developed an automatic real-time premixing inline injection system that stores water and chemical concentrates separately in different tanks and mix them directly in spray lines. The new inline injection system is able to maintain consistent chemical concentrations for the variable-rate precision sprayers with a wide dynamic range of spray outputs, and avoids long lag time, inconsistent mixture uniformity and inaccurate chemical flow rate usually associated with conventional direct inline injection systems, resulting in further improvement of spray application efficiency and environmental stewardship for variable-rate precision sprayers.

2. Development of a dedicated environmental control system to measure semiochemical release rates. Applications of semiochemicals to attract or repel insects in specific areas or to disrupt their mating have increased rapidly as a pest management strategy. Because they are safer and have minimal non-target impacts, they have been integrated with other disciplines to provide reliable and eco-friendly pest management tools for effective pest control. However, predictions of their longevity are currently hampered due to a lack of sophisticated methods to accurately monitor how the primary variables affect the semiochemical release rate. ARS researchers at Wooster, Ohio developed a controlled environmental system that was able to independently control the air temperature and relative humidity to accurately measure semiochemical release rates. Test results verified that measurements of release rates of three semiochemicals in the controlled environmental system were more precise, consistent and repeatable than measurements under field conditions. Consequently, precise quantification of semiochemical release rates for different temperatures and relative humidities with the new system will provide baselines for modelling semiochemical longevity under field conditions, for deployment of semiochemicals, and for optimization of design of semiochemical release devices.

3. Determination of foliar uptake of water droplets on waxy leaves in controlled environmental system. Improving foliar uptake of pesticides is an appropriate approach for foliar applied systemic agents to be efficient and effective. These agents require absorption of their active ingredients into the plant for sites of action. However, foliar uptake mechanism of agrochemicals still remains unclear or unknown due to lack of techniques for accurate measurements. ARS researchers at Wooster, Ohio constructed a sophisticated system that was integrated with a controlled environment chamber, a single droplet generator and a stereo microscopic imaging unit to measure foliar uptake rates of spray droplets with respect to variables of ambient temperature, droplet size, diurnal time, stoma density, osmotic pressure and droplet deposition locations on waxy leaf surfaces. This innovative technique will provide a better understanding of the transcuticular uptake mechanism of systematic compounds, and establish disciplined approaches to improve pesticide application efficacy to control target pests. This understanding will also improve efficiency for other spray applications such as plant hormones to regulate plant growth, liquid fertilizers to add supplemental nutrients to plants, and water to relieve foliar water stress during the growing season.

4. Dynamics of water droplet impact and spread on soybean leaves. Soybeans are often sprayed with hydraulic nozzles to prevent attacks by insects and diseases. Questions arise as to whether pesticide droplets continue to stay on the plants and in what deposition patterns. ARS researchers at Wooster, Ohio examined dynamics of droplet impact, rebound, retention and spread on soybean leaf surfaces under controlled conditions with different droplet sizes, impact speeds, impact angles, and leaf surface inclinations. Test results demonstrated that water droplets did not rebound while large droplets slid on the leaf surfaces. This discovery suggested that effective spray application strategies for control of soybean insects and diseases should focus on improving precision and accuracy of droplet delivery with maximal droplet coverage on leaves and minimal use of spray rates. This suggestion will help spray applicators choose optimal spray rates with proper nozzles, operating pressures and other spray parameters to increase effectiveness of controlling soybean insects and diseases.


Review Publications
Gu, J., Zhu, H., Ding, W., Wang, X. 2014. Characterization of air profiles impeded by plant canopies for a variable-rate air-assisted sprayer. Transactions of the ASABE. 57(5):1307-1315.
Shen, Y., Zhu, H. 2015. Embedded computer controlled premixing inline injection system for air-assisted variable-rate sprayers. Transactions of the ASABE. 58(1):39-46.
Dong, X., Zhu, H., Yang, X. 2015. Characterization of dynamic droplet impaction and deposit formation on leaf surfaces. Pest Management Science. 71:302-308.
Derksen, R.C., Canas, L.A., Ranger, C.M., Reding, M.E. 2015. The effect of application method on the temporal and spatial distribution of neonicotinoid insecticides in greenhouse zinnia and impact on aphid populations. Applied Engineering in Agriculture. 31:211-216.
Zhu, H., Thistle, H.W., Ranger, C.M., Zhou, H., Strom, B.L. 2015. Measurement of semiochemical release rates with a dedicated environmental control system. Biosystems Engineering. 129:277-287.
Teske, M., Thistle, H., Strom, B., Zhu, H. 2015. Development of a pheromone elution rate physical model. Biological Engineering (ASABE). 7(4):183-202.
Hadlocon, L., Soboyejo, A., Zhao, L., Zhu, H. 2015. Statistical modeling of ammonia absorption in an acid spray scrubber. Biosystems Engineering. 132:88-95.