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 Porina 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. RESULTS Using 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 7 day minimum median lethal dose of approximately 6.0 × ±1 × 106 Y. entomophaga cells per 0.02 g 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 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 (5029 kg ha−1), followed by the Y. entomophaga (4783 kg ha−1) and control (4673 kg ha−1) treatments. CONCLUSIONS The bacterium Y. entomophaga applied as a composite bait offers an environmentally sustainable approach for porina pest control. © 2019 Society of Chemical Industry

Potential for a biopesticide bait to control black beetle, Heteronychus arator (Coleoptera: Scarabaeidae)

“…Wiseana larvae also consumed only a portion of the Y. entomophaga bait presented in bioassays, with an LD 50 of 6 ± 1 × 10 6 CFU per 0.02 g of bait after 7 days. 9 The consistent mortality response, even at low doses in the bioassays, reflects a complex interrelationship between bait consumption by H. arator, growth of Y. entomophaga on the baits before ingestion, 26 and growth of Y. entomophaga after ingestion by H. arator. Although lower doses caused mortality of the target pest, these are not recommended because baits with a low bacterial load of Y. entomophaga (≤1 × 10 3 CFU g −1 ) were prone to contamination with other micro-organisms.…”

“…numbers when applied to pasture plots. 9 Heteronychus arator is a difficult pest to manage using chemical insecticides. We developed a commercial prototype product capable of controlling H. arator in large-scale field plot experiments.…”

“…(Lepidoptera: Hepialidae), which reduced larval density by 65%. 9 In the current work, we selected a model target pest (African black beetle, Heteronychus arator (Fabricius) Coleoptera: Scarabaeidae) to test a prototype biopesticide. Heteronychus arator was originally described in South Africa, where it is a pest of maize during establishment.…”

Assessment of toxicity and persistence of Yersinia entomophaga and its Yen‐Tc associated toxin

“…; Coleoptera: Chrysomelidae), 4 porina caterpillars (Wiseana spp. ; Lepidoptera: Hepialidae) 5,6 and P. xylostella. 2,3 These studies have shown that Y. entomophaga persists on apple foliage for up to two days post-spray application 4 and in moist field soil through winter at 3.27 ± 3.27 × 10 3 -3.94 ± 3.12 × 10 4 cells g -1 of soil at 112 days post-field application.…”

“…In order to address any safety concerns around the potential long-term persistence or nontarget effects of Y. entomophaga and its Yen-Tc, we used SDS-PAGE analysis and bioassays to assess the stability of the Yen-Tc following foliar application, exposure to UV, or incubation with the intestinal fluids of Yen-Tc-susceptible scarabs (Coleoptera, Scarabaeidae) C. giveni and Adoryphorus couloni (red headed cockchafer), and the nonsusceptible lepidopteran species H. armigera. Through the application of Y. entomophaga to pastures for the control of porina 5,6 or other pastoral pests, the applied bacterium may be ingested by grazing animals. For this reason, the stability profile of the Yen-Tc also was assessed in the rumen fluid of Holstein Friesian cows (Bos taurus) and Romney sheep (Ovis aries).…”