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

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.

A risk-based detection survey for the predatory mirid Macrolophus pygmaeus in New Zealand.

Macrolophus pygmaeus, a predatory mirid used to manage greenhouse whitefly, was illegally imported into New Zealand, and for a time was reared and sold to commercial tomato growers. We designed and implemented a risk-based detection survey to determine whether M. pygmaeus was still present in New Zealand a decade later. The survey was designed to have an 80% chance of detecting a single low density (0.05 per lineal metre of host plants) population within 1 km of known points of introduction. The survey was implemented between 8 and 15 March 2018. Local habitat constraints meant that the planned sampling had to be modified but this was accounted for in the subsequent analysis. No M. pygmaeus were found in the samples, but 93 specimens from seven other mirid taxa were detected, validating the sample methods. The survey gives 60% confidence that M. pygmaeus was not present at a mean density of 0.05 per lineal metre of habitat. It gives 80% confidence that a population at 0.1 m-1 was not present and 90% confidence that no population exists at >0.18 m-1. Though there are no published data on typical field population densities of M. pygmaeus, for related species the survey would have had high confidence in detecting any medium to high density population present. Therefore, it is likely that M. pygmaeus is no longer present in New Zealand, but if extant within the sampled areas then we have high certainty that it was at low densities compared to other predaceous mirids.

When field experiments yield unexpected results: lessons learned from measuring selection in White Sands lizards.

Determining the adaptive significance of phenotypic traits is key for understanding evolution and diversification in natural populations. However, evolutionary biologists have an incomplete understanding of how specific traits affect fitness in most populations. The White Sands system provides an opportunity to study the adaptive significance of traits in an experimental context. Blanched color evolved recently in three species of lizards inhabiting the gypsum dunes of White Sands and is likely an adaptation to avoid predation. To determine whether there is a relationship between color and susceptibility to predation in White Sands lizards, we conducted enclosure experiments, quantifying survivorship of Holbrookia maculate exhibiting substrate-matched and substrate-mismatched phenotypes. Lizards in our study experienced strong predation. Color did not have a significant effect on survival, but we found several unexpected relationships including variation in predation over small spatial and temporal scales. In addition, we detected a marginally significant interaction between sex and color, suggesting selection for substrate matching may be stronger for males than females. We use our results as a case study to examine six major challenges frequently encountered in field-based studies of natural selection, and suggest that insight into the complexities of selection often results when experiments turn out differently than expected.

The role of humans in the importation of ticks to New Zealand: a threat to public health and biosecurity.

Humans coming into New Zealand occasionally, and unwittingly, bring exotic ticks with them, either attached to their bodies or with luggage. Of the 172 available records for tick interception at New Zealand's border, half can be attributed to human agency. Here, together with an outline of tick biology and ecology, we present evidence of at least 17 species of ticks being brought in by humans, with Australia, North America and Asia the most frequent countries of origin. Risks posed by some of the nine species of ticks already in New Zealand are briefly examined. Sites of attachment of ticks and associated symptoms where these have been recorded are presented. Diseases transmitted by ticks and most likely to be encountered by travellers are briefly discussed together with the most practical method of tick removal. A plea is made for practitioners to increase their awareness of the risks to New Zealand's biosecurity and public health posed by ticks and to ensure that as many as possible of these unwelcome 'souvenirs' are collected and passed on for identification.

Population dynamics and gene flow of Helicoverpa armigera (Lepidoptera: Noctuidae) on cotton and grain crops in the Murrumbidgee Valley, Australia.

The population dynamics of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in the Murrumbidgee Valley, Australia, has been characterized using five highly variable microsatellite loci. In the 2001-2002 growing season, there were very high levels of migration into the Murrumbidgee Valley with no detectable genetic structuring, consistent with previous analyses on a national scale. By contrast, there was significant genetic structuring over the 2002-2003 growing season, with three distinct genetic types detected. The first type corresponded to the first two generations and was derived from local individuals emerging from diapause and their progeny. The second genetic type corresponded to generation 3 and resulted from substantial immigration into the region. There was another genetic shift in generation 4, which accounts for the third genetic type of the season. This genetic shift occurred despite low levels of immigration. During the third generation of the 2002-2003 growing season, different population dynamics was characterized for H. armigera on maize, Zea mays L., and cotton Gossipium hirsutum L. Populations on cotton tended to cycle independently with very little immigration from outside the region or from maize within the region. Maize acted as a major sink for immigrants from cotton and from outside the region. If resistance were to develop on cotton under these circumstances, susceptible individuals from maize or from other regions would not dilute this resistance. In addition, resistance is likely to be transferred to maize and be perpetuated until diapause, from where it may reemerge next season. If low levels of immigration were to occur on transgenic cotton, this may undermine the effectiveness of refugia, especially noncotton refugia.