The effects of insecticide seed treatments on the parasitism and predation of Myzus persicae (Homoptera: Aphididae) in canola.

The green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), is a major pest of brassica plants, with the ability to transmit > 100 viruses. Although the adoption of Integrated Pest Management is increasing, chemical treatment remains the predominant method used to control M. persicae globally. Insecticide seed treatments, typically with neonicotinoid active ingredients, have become commonplace in canola crops, and are viewed as a "softer" alternative to foliar sprays but may nevertheless impact natural enemies of M. persicae. In this study, the effects of canola seed treatments, containing imidacloprid, thiamethoxam, and a mixture of thiamethoxam + lambda-cyhalothrin, were investigated on the parasitoid wasp, Aphidius colemani Viereck (Hymenoptera: Braconidae) and the green lacewing, Mallada signatus (Schneider) (Neuroptera: Chrysopidae), both important natural enemies of M. persicae. Laboratory trials were undertaken using whole plants, with lethal and sublethal effects assessed by measuring several traits. Compared with untreated plants, more aphid mummies were produced and more A. colemani were reared on plants treated with thiamethoxam + lambda-cyhalothrin and more aphid mummies were produced on imidacloprid plants. Imidacloprid reduced the time A. colemani spent searching for M. persicae and thiamethoxam reduced its cleaning time. However, after A. colemani were removed from treated plants, there were no such effects observed, suggesting these impacts were relatively short-lived. We found no significant effects of seed treatments on M. signatus. These results point to the complexity of ecotoxicology studies involving multiple trophic levels and indicate that seed treatments may have variable impacts on key fitness traits of natural enemies.

Economic Injury Levels and Dynamic Action Thresholds for Diuraphis noxia (Hemiptera: Aphididae) in Australian Cereal Crops.

The Russian wheat aphid (Diuraphis noxia [Kurdjumov, Hemiptera: Aphididae], RWA) was first detected in Australia in 2016 and is threatening an annual cereal industry valued at nearly 10 billion AUD per annum. Considerable uncertainty surrounds the economic risk of D. noxia to Australian cereals, which limits cost-effective farm management decisions. Through a series of inoculated and non-inoculated field trials in 2018 and 2019 in south-eastern Australia, we generated a range of D. noxia pressure metrics under different growing conditions for barley, wheat, and durum wheat. Relative yield loss was best explained by the 'percentage of tillers with D. noxia' (%TwRWA) with 0.28% yield loss per percent of tillers with D. noxia, which is significantly lower than 0.46-0.48% for susceptible winter wheat varieties in dryland conditions in the United States. Highest infestation levels were typically reached around GS40-50. To develop an action threshold, we calculated the rate of increase in the %TwRWA through time at 0.021% per day per %TwRWA (with little variation across sites). This allowed prediction of the expected maximum %TwRWA based on observations post tillering (GS30) and the expected duration before GS50 is reached. For earlier growth stages (

Lifecycle of the invasive omnivore, Forficula auricularia, in Australian grain growing environments.

BACKGROUND: The European earwig, Forficula auricularia (L.) (Dermaptera: Forficulidae), is regarded as an important beneficial in many orchard environments but has the potential to be a plant pest in other systems, including to grain crops. Due to its agricultural importance, the lifecycle of F. auricularia has been widely studied in North America and Europe. However, much less is known in the southern hemisphere, including Australia where F. auricularia has been present for over 170 years. RESULTS: To elucidate the lifecycle of F. auricularia, we monitored five sites in grain-growing areas of southern Australia using two different trap types. Adults were found year-round, but most prevalent from late-spring to mid-winter. First instars were typically found from mid to late winter. Second, third and fourth instars occurred from winter through to late spring. The seasonal development of F. auricularia in Australia may be much earlier than observed in comparable North American studies. Degree day modelling highlights variation in development times across the active season for F. auricularia across our sites. CONCLUSION: Forficula auricularia is well adapted to the Australian grain growing environments. The timing of egg hatching aligns closely with crop emergence, juveniles then develop alongside the crop, and adult development occurs by harvest time in late spring. These findings are important given that many of these crops (canola, lucerne, pulses) are vulnerable to attack by F. auricularia during emergence and development. They also suggest a phenotypic capacity of this species to adapt different phenology after introduction into a novel environment. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Morphological and Molecular Analysis of Australian Earwigs (Dermaptera) Points to Unique Species and Regional Endemism in the Anisolabididae Family.

Dermaptera (earwigs) from the Anisolabididae family may be important for pest control but their taxonomy and status in Australia is poorly studied. Here we used taxonomic information to assess the diversity of southern Australian Anisolabididae and then applied cox1 barcodes as well as additional gene fragments (mitochondrial and nuclear) to corroborate classification and assess the monophyly of the putative genera. Anisolabididae morphospecies fell into two genera, Anisolabis Fieber and Gonolabis Burr, based on paramere morphology. Combinations of paramere and forceps morphology distinguished seven morphospecies, which were further supported by morphometric analyses. The morphospecies were corroborated by barcode data; all showed within-species genetic distance < 4% and between-species genetic distance > 10%. Molecular phylogenies did not support monophyly of putative genera nor clades based on paramere shape, instead pointing to regional clades distinguishable by forceps morphology. This apparent endemism needs to be further tested by sampling of earwig diversity outside of agricultural production regions but points to a unique regional insect fauna potentially important in pest control.

Complete mitochondrial genome of the European Grapevine moth (EGVM) Lobesia botrana (Lepidoptera: Tortricidae).

The Lobesia botrana larvae feed on grapevine (Vitis vinifera L.), thereby reducing crop yield and increasing crop susceptibility to fungal and bacterial attacks. We determined the circular mitochondrial genome of L. botrana as 15 229 bp (GenBank KP677508) and contained 13 protein coding genes (PCG's), 22 transfer RNAs (tRNA), and two ribosomal RNAs. All tRNAs have the "clover-shaped" 2-D structures, while the tRNA-Ile which has the TψC-stem but lacked the TψC-loop. Knowledge of L. botrana mitochondrial genome represents a valuable molecular resource for developing effective DNA identification tools for biosecurity purposes and will contribute to better understanding of its evolutionary and population genetics.

Microsatellite and mitochondrial data provide evidence for a single major introduction for the Neartic leafhopper Scaphoideus titanus in Europe.

Scaphoideus titanus, a leafhopper native to North America and invasive in Europe, is the vector of the Flavescence dorée phytoplasma, the causal agent of the most important form of grapevine yellows in European vineyards. We studied 10 polymorphic microsatellite loci and a 623 bp fragment of the mitochondrial cytochrome oxidase II gene in native S. titanus from north-eastern America and introduced European populations, to elucidate the colonization scenario. Consistent with their recent history, invasive European populations were less genetically diverse than American populations for both types of markers, suggesting a recent bottleneck. Significant isolation by distance was detected between American populations but not between European populations. None of the European mitochondrial haplotypes was found in the American vineyards, from which they are assumed to have originated. The precise source of the invasive S. titanus populations therefore remains unclear. Nevertheless, the high heterozygosity of North-East American populations (which contained 92% of the observed alleles) suggests that this region is part of the native range of S. titanus. Clustering population genetics analyses with microsatellite and mitochondrial data suggested that European populations originated from a single introduction event. Most of the introduced populations clustered with populations from Long Island, the Atlantic Coast winegrowing region in which Vitis aestivalis occurs.

Control of Xiphinema index populations by fallow plants under greenhouse and field conditions.

The dagger nematode Xiphinema index has a high economic impact in vineyards by direct pathogenicity and above all by transmitting the Grapevine fanleaf virus (GFLV). Agrochemicals have been largely employed to restrict the spread of GFLV by reducing X. index populations but are now banned. As an alternative to nematicides, the use of fallow plants between two successive vine crops was assessed. We selected plant species adapted to vineyard soils and exhibiting negative impact on nematodes and we evaluated their antagonistic effect on X. index in greenhouse using artificially infested soil, and in naturally infested vineyard conditions. The screening was conducted with plants belonging to the families Asteraceae (sunflower, marigold, zinnia, and nyjer), Poaceae (sorghum and rye), Fabaceae (white lupin, white melilot, hairy vetch, and alfalfa), Brassicaceae (rapeseed and camelina), and Boraginaceae (phacelia). In the greenhouse controlled assay, white lupin, nyjer, and marigold significantly reduced X. index populations compared with that of bare soil. The vineyard assay, designed to take into account the aggregative pattern of X. index distribution, revealed that marigold and hairy vetch are good candidates as cover crops to reduce X. index populations in vineyard. Moreover, this original experimental design could be applied to manage other soilborne pathogens.

Genetic signature of amphimixis allows for the detection and fine scale localization of sexual reproduction events in a mainly parthenogenetic nematode.

Asexuality is an important mode of reproduction in eukaryotic taxa and has a theoretical advantage over sexual reproduction because of the increased ability to propagate genes. Despite this advantage, hidden signs of cryptic sex have been discovered in the genomes of asexual organisms. This has provided an interesting way to address the evolutionary impact of sex in plant and animal populations. However, the identification of rare sexual reproduction events in mainly asexual species has remained a challenging task. We examined the reproductive history in populations of the plant parasitic nematode Xiphinema index by genotyping individuals collected from six grapevine fields using seven microsatellite markers. A high level of linkage disequilibrium and heterozygous excess suggested a clonality rate of 95-100%. However, we also detected rare sexual reproduction events within these highly clonal populations. By combining highly polymorphic markers with an appropriate hierarchical sampling, and using both Bayesian and multivariate analysis with phylogenetic reconstructions, we were able to identify a small number of sexually produced individuals at the overlapping zones between different genetic clusters. This suggested that sexual reproduction was favoured when and where two nematode patches came into contact. Among fields, a high degree of genetic differentiation indicated a low level of gene flow between populations. Rare genotypes that were shared by several populations suggested passive dispersal by human activities, possibly through the introduction of infected plants from nurseries. We conclude that our method can be used to detect and locate sexual events in various predominantly asexual species.