Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 1998
Publication Date: N/A
Technical Abstract: The L. decemlineata-control potential of Beauveria bassiana was evaluated. Applications were made in small plots (6 rows by 12 m) using a backpack sprayer fitted with three hollow-cone nozzles. The center nozzle was mounted on a fixed tube and sprayed straight downward from 15-20 cm above the crop canopy. Each of the lateral nozzles was mounted on a swivel affixed to a drop tube; these nozzles were carried 15-20 cm above the ground and were directed upward at a 45 angle. The sprayer delivered 280 l/ha at 60 psi. Three doses (1.25, 2.5, and 5 x 1013 conidia/ha) of an oil-based formulation of B. bassiana strain GHA and two spray intervals (3-4 versus 7 d) were tested. Three sprays of the intermediate and high doses applied at 3-4 d intervals produced equivalent control of approx. 70%. The low dose and sprays at weekly intervals were less effective. A wettable powder formulation was also compared to the oil formulation. Three sprays at the intermediate rate were applied at 3-4 d intervals. Rainfall closely followed two of the three applications. The oil formulation was significantly more effective than the WP formulation under these conditions (approx. 70 vs 20% control), suggesting greater rain fastness of the oil formulation. Tests with the oil formulation also compared applications from a sprayer configured as described above to those from a sprayer configured with three nozzles directed to spray downward from approx 30 cm above the canopy. The sprayer with drop tubes deposited 2,300 spores/mm2 onto the upper surfaces of the leaves and 680 spores/mm on the lower surfaces, while the alternative sprayer deposited 2,100 versus 80 spores/mm2 onto the respective leaf surfaces. The applications from below canopy provided greater control (70 vs 16%).