Development of a Yersinia entomophaga bait for control of larvae of the porina moth (Wiseana spp.), a pest of New Zealand improved grassland systems.

Abstract

BACKGROUND\nPorina is the common name for moths and larvae of the genus Wiseana (Lepidoptera: Hepialidae), some of which are significant pasture pests in New Zealand. Because of environmental concerns and the non-target effects of insecticide control measures, biological alternatives for the control of insect pests such as porina are required.\n\n\nRESULTS\nUsing a food preference assay and time-lapse photography, a range of low-cost food ingredients were assessed for their palatability to porina larvae. Lead candidates were combined into extruded bait variants, allowing assessment of their palatability to porina larvae. A composite bait consisting of palatable ingredients was developed, into which the porina-active entomopathogen Yersinia entomophaga was incorporated. A seven day minimum median lethal dose of approximately 6.0 x ±1 x106 Y. entomophaga cells per 0.02 gram of bait was defined. Field trials showed that the mean change in larval density over time differed between treatments, with Y. entomophaga bait applied at 87 kg ha-1 resulting in a mean 65% reduction in larval density relative to the control plots, and the diflubenzuron treatment resulting in a mean 77% reduction relative to the control plots. The mean dry matter yields over the course of the trial were highest for diflubenzuron (5,029 kg ha-1 ), followed by the Y. entomophaga (4,783 kg ha-1 ) and control (4,673 kg ha-1 ) treatments.\n\n\nCONCLUSIONS\nThe bacterium Y. entomophaga applied as a composite bait offers an environmentally sustainable approach for porina pest control. This article is protected by copyright. All rights reserved.