Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2007
Publication Date: 7/2/2007
Citation: Fife, J.P., Ozkan, H.E., Derksen, R.C., Grewal, P.S. 2007. Effects of Pumping on Entomopathogenic Nematodes and Temperature Increase within a Spray System. Applied Engineering in Agriculture. 23(4):406-412. Interpretive Summary: Despite the advantages of using biopesticides, grower use of them as alternatives to chemical pesticides has been limited, in part, to a lack of understanding of how to handle and deliver them in a manner that will not reduce viability. The objective of this research was to determine which factors, mechanical or thermal, could be most detrimental to a biopesticide. Entomopathogenic nematodes (EPN) were chosen as the benchmark biological management organism. Laboratory experiments were designed to study the effect that movement through flow control valves and common agricultural spray pumps would have on nematode viability. The types of pumps studied included centrifugal, roller, and diaphragm. Additional laboratory experiments were established to study how much the temperature of the spray mix would change with multiple recirculations of spray tank mix through the three pumps. The tests found that a single pass of the EPN through the selected valves and pumps did not significantly affect EPN viability. Continual circulation of the tank mix through the pumps to provide hydraulic agitation increased the temperature of the tank mix. Multiple recirculations of 12 gallons of water over 2 h with the centrifugal pump produced the greatest increase in temperature (33 degrees C). A temperature increase of 3-6 degrees C was also noted when the centrifugal pump was used to circulate and deliver tank mix from a 300 gallon, commercial sprayer. These results can alert equipment manufacturers and biopesticide suppliers to potential conditions that could affect EPN viability and to provide alternate sprayer designs to minimize the risk of thermal stress on EPN.
Technical Abstract: Moving biological pesticide through spray systems could create hydrodynamic stresses and increase fluid temperature to a point which could cause damage and reduce viability of the living organism. Laboratory experiments were conducted to evaluate damage caused to a benchmark biopesticide, entomopathogenic nematodes (EPN), following passage through valves and pumps commonly found on commercial agricultural spray equipment. Single passage through centrifugal, diaphragm, and rollers pumps did not damage the EPN. Passage through flow control valves did not damage the EPN. Spray tank mix temperature increases were noted for all pumps used to circulate the spray mix and was greatest for the centrifugal pump after 2 h tests. A centrifugal pump was also used to circulate spray mix in a 300 gal conventional sprayer. The temperature increases were 3.2 and 6.5 degrees C over a 3 h period of circulating a full tank and emptying a full tank, respectively. These results indicate that temperature increases of the spray mix may be a greater problem for maintaining the viability of biopesticides than mechanical stresses. Low-volume pumps are better suited for delivering biopesticides such as EPN because they do not increase the temperature of the tank mix as much as high-volume centrifugal pumps.