In grain crops, aphids are important pests, but they can be suppressed by hymenopteran parasitoids. A challenge in incorporating parasitoids into Integrated Pest Management (IPM) programs, however, is that parasitoid numbers can be low during periods within the season when aphids are most damaging. Understanding the population dynamics of key aphid species and their parasitoids is central to ameliorating this problem. To examine the composition and seasonal trends of both aphid and parasitoid populations in south-eastern Australia, samples were taken throughout the winter growing seasons of 2017 and 2018 in 28 fields of wheat and canola. Myzus persicae (Sulzer) was the most abundant aphid species, particularly within canola crops. Across all fields, aphid populations remained relatively low during the early stages of crop growth and increased as the season progressed. Seasonal patterns were consistent across sites, due to climate, crop growth stage, and interactions between these factors. For canola, field edges did not appear to act as reservoirs for either aphids or parasitoids, as there was little overlap in the community composition of either, but for wheat there was much similarity. This is likely due to the presence of similar host plants within field edges and the neighbouring crop, enabling the same aphid species to persist within both areas. Diaeretiella rapae (M’Intosh) was the most common parasitoid across our study, particularly in canola, yet was present only in low abundance at field edges. The most common parasitoid in wheat fields was Aphidius matricariae (Haliday), with field edges likely acting as a reservoir for this species. Secondary parasitoid numbers were consistently low across our study. Differences in parasitoid species composition are discussed in relation to crop type, inter-field variation, and aphid host. The results highlight potential focal management areas and parasitoids that could help control aphid pests within grain crops.
The Russian wheat aphid, Diuraphis noxia (Mordvilko ex Kurdjumov), is one of the world's most economically important pests of grain crops and has been recorded from at least 140 grass species within Poaceae. It has rapidly dispersed from its native origin of Central Asia into most major grain-producing regions of the world including Africa, Asia, Europe, the Middle East, North America and South America. Diuraphis noxia was first found in Australia in a wheat crop in the mid-north of South Australia in May 2016. Since then, D. noxia has been recorded throughout grain-growing regions of South Australia, Victoria, New South Wales and Tasmania. The distribution will continue to expand, with climatic suitability modelling suggesting D. noxia can persist in all key grain regions, including large parts of Western Australia and Queensland. Australian populations of D. noxia appear to be anholocyclic, with no sexual stages being observed. The aphids can reproduce year round as long as host plants are available. Australian farmers have generally adopted prophylactic insecticide seed treatments and/or foliar sprays to manage D. noxia. Research is required to fully understand yield impacts, host preferences and host plant resistance associated with D. noxia. Cultural control through managing alternate host plants over summer, agronomic crop management, biological control and developments in host plant resistance should provide considerable future benefits. Key wordsexotic pest, invasion, management, review, Russian wheat aphid. DESCRIPTIONOriginally named Brachycolus noxius, the Russian wheat aphid (now known as Diuraphis noxia) was first recognised as a separate species by Mordvilko in a paper by Kurdjumov (1913). Detailed descriptions of D. noxia have been provided by Blackman and Eastop (1984) and Stoetzel (1987). In brief, D. noxia has an elongated, spindle-shaped body, with the tips of the legs and distal third of the (distinctively short) antennae black. The wings *pumina@unimelb.edu.au
The Indonesian species of the family Signiphoridae (Hymenoptera, Chalcidoidea) are revised. Three species of Chartocerus are described as new (Chartocerus kartiniae Polaszek & Schmidt, sp. nov., C. sumatrensis Schmidt & Polaszek, sp. nov., and C. javensis Schmidt & Ubaidillah, sp. nov.) and four species of Signiphora, viz., S. bennetti Woolley & Dal Molin, S. flavella Girault, S. perpauca Girault and S. bifasciata Ashmead, are diagnosed.
Aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) were surveyed within grain production landscapes in Victoria, Australia, between 2017 and 2018, as well as more sporadically nationwide between 2016 and 2019. In addition, Aphidiinae records were collated from insect depositories around Australia and online databases. The 5525 specimens recorded constituted a total of 23 species and seven genera. Diaeretiella rapae (M'Intosh) was the most common species, representing more than 70% of all Aphidiinae recorded. This species also showed a greater northerly geographical range than other Aphidiinae. During sampling between 2017 and 2019, Aphidiinae were reared from mummies to ascertain host-parasitoid relationships. Diaeretiella rapae was again the most commonly reared parasitoid, although parasitoid preference varied with aphid host and between states and territories. An illustrated dichotomous key to Australian Aphidiinae in grain production landscapes is provided for the 11 species sampled in our field surveys. This is the first comprehensive review of Aphidiinae sampled within Australia in over two decades. Knowledge about the diversity and distribution of these parasitoids is important for understanding their impact on current and future invasions of aphid species. In addition, understanding the interactions between grain aphids and their associated parasitoids will further support the inclusion of parasitoid wasps into integrated pest management (IPM) strategies.
Background: Estimating parasitoid abundance in the field can be difficult, even more so when attempting to quantify parasitism rates and theecosystemserviceofbiologicalcontrol thatparasitoidscanprovide.Tounderstandhow'field observed'parasitismrates(in-field mummy counts) of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) translate to 'laboratory observed' parasitism rates (laboratory-reared parasitoid counts), field work was undertaken in Australian canola fields, over the winter growing season.Results: Overall, laboratory observed parasitism was on average 2.4 times higher than field observed parasitism, with rates an average of four-fold higher in fields from South Australia. Total field observed and laboratory observed parasitism rates (OPRs) of M. persicae varied considerably across regions, but less so among fields within regions. As crop growth stage progressed, the incidence of field observed mummies increased. The incidence of total parasitoids reared also increased with crop growth stage, averaging 3.4% during flowering and reaching 14.4% during podding/senescing. Although there was a greater diversity of reared parasitoid species at later crop growth stages, the laboratory OPR was unaffected by parasitoid species. Diaeretiella rapae was the most commonly reared parasitoid, increasing in absolute abundance with crop growth stage.Conclusion: These findings indicate that field mummy counts alone do not provide a clear representation of parasitism within canola fields.
BACKGROUND: Estimating parasitoid abundance in the field can be difficult, even more so when attempting to quantify parasitism rates and the ecosystem service of biological control that parasitoids can provide. To understand how observed parasitism rates (in-field mummy counts) of the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae) translate to actual parasitism rates (laboratory-reared parasitoid counts), field work was undertaken in Australian canola fields over a growing season. Parasitoids were reared within a controlled laboratory setting. RESULTS: Total observed and actual parasitism rates of M. persicae varied considerably across regions, but less so on a field level. Overall, actual parasitism was on average 2.4 times higher than that observed in the field, with rates an average of 4-fold higher in South Australia. As crop growth stage progressed, the percentage of mummies observed increased. Percentage of parasitoids reared also increased with crop growth stage, averaging 3.4% during flowering and reaching 14.4% during podding/senescing. Although there was a greater diversity of reared parasitoid species at later crop growth stages, actual parasitism rate was unaffected by parasitoid species. Diaeretiella rapae was the most commonly reared parasitoid, increasing in abundance with crop growth stage. CONCLUSION: These findings indicate that mummy counts alone do not provide a clear representation of parasitism within fields.
BackgroundThe genus Cales has been extensively revised recently and divided into two species groups, the noacki- and spenceri-groups Mottern et al. (2010), Mottern and Heraty (2014).New informationCales motterni Polaszek, Shih & Ward sp. nov. is described from two females reared from the whitefly Bemisia pongamiae from Taiwan. The species belongs to the spenceri- group, and has a characteristic and unusual antennal clava. A key to the four species currently known from the spenceri-group is provided.
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