Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 10, 2004
Publication Date: February 10, 2005
Citation: Fife, J.P., Ozkan, H.E., Derksen, R.C., Grewal, P.S., Krause, C.R. 2005. Viability of a Biological Pest Control Agent Through Hydraulic Nozzles. Transactions of the ASAE. 48(1):45-54. Interpretive Summary: Biopesticides are becoming more widely available as pest management alternatives. Significant efforts have been made in production and formulation technologies for biopesticides but there are few guidelines available on how to apply these to full size fields and landscape. The objective of this research was to evaluate flow conditions through common types of agricultural nozzles and make recommendations on sprayer components that do not pose a significant risk to biopesticide viability. Entomopathogenic nematodes (EPN) were chosen as the benchmark biological management organism. Computer simulations and bench-top experiments were used to identify operating conditions that might be harmful to EPN. The computer simulations suggested that the extensional type of flow through a relatively small flat fan nozzle could potentially cause more EPN damage compared to the high rotational flow component produced during flow though a hollow cone nozzle. Great reductions in EPN viability were observed following flow through a flat fan nozzle used on the opposed-piston device compared to flow through a relatively small, hollow cone nozzle. The computer simulations appear to support the experimental observations. In addition, there appear to be significant differences in how different EPN species responded to flow through the bench-top device. These tests demonstrate that delivery nozzle size should be matched to the size of EPN. By identifying the advantages of using cone-type of nozzles compared to flat fan nozzles for delivery of biopesticides, this research demonstrates to private and commercial applicators how to maximize EPN viability to help maintain biological efficacy.
Technical Abstract: Hydrodynamic stresses during flow though pesticide sprayers could damage biological organisms being applied to full size fields and landscape. The objective of this work was to characterize damage done to biological pest control agent, entomopathogenic nematodes (EPN), during delivery through conventional spray nozzles. Liquid suspensions of EPNs were passed through three different common hydraulic nozzles (flat fan, hollow cone, full cone) within a bench-top, opposed-piston flow device. Computational fluid dynamics (CFD) was used to simulate internal flow through the flat fan and hollow cone nozzles. Flow field parameters from the CFD simulations were compared to the observed EPN relative viability after treatment. Bench tests revealed that flow through the flat fan nozzle was more damaging compared to flow through the hollow cone nozzle. CFD simulations showed that average energy dissipation rates within the flat fan exit orifice were significantly higher than simulations predicted for flow through hollow cone nozzles. Higher energy dissipation rates corresponded to greater reduction in EPN viability following passage through the flat fan nozzle. CFD simulations demonstrated that tensile stresses developed in the extensional flow regime at the flat fan exit orifice were likely the cause of nematode damage. Similar conditions did not exist at the exit of the hollow cone nozzle. Because the flow rates tested were considerably higher than seen under normal operating conditions, these nozzles are acceptable for delivery of EPNs in dilute, aqueous, suspensions. Based on the simulations and bench tests, a cone nozzle is more suitable for EPN delivery than a fan nozzle type.