Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 28, 2008
Publication Date: August 3, 2008
Citation: Wraight, S.P., Ramos, M. 2008. Improving efficacy of Beauveria bassiana foliar treatments against Colorado potato beetle via manipulation of spray-application parameters. Society for Invertebrate Pathology Annual Meeting. 41:80. Technical Abstract: Effects of hydraulic spray pressure and sprayer configuration on efficacy of foliar applications of B. bassiana against Leptinotarsa decemlineata larvae were evaluated during 4 field seasons. Treatments were applied to small plots using a tractor-mounted sprayer with nozzles mounted on swivels on short drop tubes spaced 21.5 cm apart. Nozzles (4/potato row) were positioned at canopy height and directed forward and downward at a 45 deg angle. The sprayer was alternatively configured with nozzles mounted on double swivels on drop tubes centered between the rows. Nozzles (2/row) were positioned at ca. mid crop height, directed perpendicular to the row, and angled upward at an 85 deg angle. Hollow-cone nozzles of 4 sizes were selected to deliver a constant volume of ca. 467 L/ha at 4 different pressures: 4 nozzles/row @ 345 kPa (configuration A), 690 kPa (B), and 2,758 kPa (C); 2 nozzles/row @ 621 kPa (D). Conidia formulated as a wettable powder were applied 3–4 times/season at 3–5-day intervals. Each application was made at the rate of 2.5 E13 conidia/ha; treatments included untreated and spray-carrier controls. Significantly greater larval mortality resulted from the C vs. A and B configurations (34 vs. 12 and 15%, respectively). Results from the D configuration (29% mortality) were equivalent to C. The C and D configurations also produced greater reductions in 2nd-generation adult populations than the A and B configurations (86 & 87% vs. 75 & 81%, respectively); however, treatment differences were not significant. This study indicates that modifying spray parameters can increase efficacy of biopesticide sprays against potato beetles; however, the increases we observed were small and may not justify the added costs associated with the required modifications.