Hymenopteran Parasitoids of Aphid Pests within Australian Grain Production Landscapes

Abstract

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.

Livin' on the edge: precision yield data shows evidence of ecosystem services from field boundaries.

“…While we consider microclimate to be the most likely cause of the intermediate increase, it may also be related to soil effects from shelterbelts, where erosion is reduced and leaf litter from the shelterbelt can cause an increase in soil deposition . Finally, shelterbelts may also act as sources of predators or parasitoids of wheat crop pests (Dong et al 2015;Ward et al 2021) but their effect depends on pest pressures, which are typically suppressed by pesticide application. We recommend that follow-up studies a) use precision yield data to confirm that this pattern exists across broader geographical areas and b) examine the influence of the three potential mechanisms considered above (as well as their interaction).…”

The effects of insecticide seed treatments on green peach aphid Myzus persicae (Sulzer) (Homoptera: Aphididae) parasitism by Aphidius colemani Viereck (Hymenoptera: Aphidiidae) and predation by Mallada signatus (Schneider) (Neuroptera: Chrysopidae)

“…Further experiments should also be undertaken with other species to determine how widespread these patterns are across taxa. One species of particular importance in grain crops is Diaeretiella rapae (M'Intosh), which is the most commonly found aphidiine in canola fields in Australia (Ward et al, 2021). Globally, there is very little data on the toxicity of insecticide products against this species.…”

Study of aphid parasitoids (Hymenoptera: Braconidae) in Australian grain production landscapes

“…We undertook both direct sampling of parasitoids and direct sampling of mummies to subsequently rear parasitoids. The rearing protocol followed that outlined above and in Ward et al (2021a).…”