/pdf/spillover-of-functionally-important-organisms-between-5ewg03t2bw.pdf

Spillover of functionally important organisms between managed and natural habitats

We describe polymerase chain reaction (PCR) primers for gut analysis of aphid predators. The primers amplify aphid mitochondrial COII fragments ranging in size from 77 to 386 bp. Using these primers, we were able to distinguish six species of US Great Plains cereal aphids, including two congeners, Rhopalosiphum maidis (Fitch) and R. padi (L.), and to detect them in extracts of coccinellid and chrysopid predators. We devised a protocol for deriving half-lives of detectability for the DNA of a single aphid consumed by predators maintained under simulated field dietary and temperature conditions. Using this protocol and primers that amplify a 198-bp fragment, we determined statistically different half-lives of detectability for a single R. maidis of 3.95 h in Chrysoperla plorabunda (Fitch) and 8. 78 h in Hippodamia convergens Guerin. The detectability half-life for a 339-bp R. maidis fragment was statistically longer in C. plorabunda but not in H. convergens. The sensitivity of the assay for the 198-bp fragment is 10-7 aphid equivalents. For species-specific predator gut analysis, PCR is superior to monoclonal antibody technology, giving comparable detectability half-lives with lower expense, much shorter development times, and greater certainty of a successful outcome.

Identifying key cereal aphid predators by molecular gut analysis

Ecologists have quantified Orthoptera (grasshoppers and crickets) density in a wide variety of conservation studies. Objective determination of Orthoptera population size is possible using mark-release recapture techniques but these are time-consuming and of little use for all but the smallest scale studies. Therefore, a wide range of sampling techniques have been devised to quantify population density and the most commonly used methods include sweep netting and quadrat counts. It is the aim of this paper to critically review studies that have used these techniques and to provide useful suggestions for non-specialists on which method may be most applicable to their study site. This paper reviews a selection of the extensive literature reporting studies estimating the abundance of grasshoppers (Acrididae) in a wide range of grassland ecosystems. Where possible, studies on bush-crickets (Tettigoniidae) and crickets (Gryllidae) are included reflecting their overall contribution to assemblage diversity in grassland ecosystems and to highlight the need for further investigations of sampling efficiency on these two under-researched families.

Review of the Methods Frequently Used to Estimate the Abundance of Orthoptera in Grassland Ecosystems

The predator and parasitoid fauna associated with cereal aphids is described, emphasizing the fauna associated with classical biological control efforts against the greenbug and Russian wheat aphid. We focus on literature from North America and include work from Europe and elsewhere when it is desirable to draw contrasts between approaches that affect cereal aphid biological control. Effects on natural enemies of cereal aphids are described that appear associated with plant traits that are innate, bred, or induced by aphid feeding. Examples of habitat manipulations, within and bordering cereal fields and within the broader landscape in which cereal production resides, affecting predators and parasitoids of cereal aphids are presented. These mediating effects of host plant and habitat manipulations on cereal aphid biological control provide significant and underexplored avenues to optimize cereal aphid management.

/pdf/biological-control-of-cereal-aphids-in-north-america-and-363j42zo8r.pdf

Biological control of cereal aphids in north america and mediating effects of host plant and habitat manipulations.

Breeding Wheat for Resistance to Insects

Host aphids of the parasitoid Diaeretiella rapae (M’Intosh,) are defined for Washington State, together with a listing of world findings. Specifics are given on host habitats frequented by the parasitoid, comparative population abundance, associated parasitoid species, and host switching. D. rapae is a common parasitoid of Brachycorynella asparagi (Mordvilko), Hayhurstia atriplicis (L.), Brevicoryne brassicae (L.), Diuraphis noxia (Kurdjumov), and sometimes Myzus persicae (Sulzer). In total, 19 species of aphids were positively linked with D. rapae and 6 are reported as hosts for the first time— Acyrthosiphon lactucae (Passerini), Phorodon humuli (Schrank), Dysaphis plantaginea (Passerini), Brachycaudus tragopogonis (Kaltenbach), Uroleucon ivae Robinson, and Braggia sp. D. rapae was shown to switch or alternate successfully between hosts, which suggests that certain host habitats might be used in conjunction with farmlands to enhance host opportunities for the parasitoid and improve its population stability. Two of its primary aphid hosts, B. asparagi and D. noxia, reached pest status shortly after their arrival in Washington but are less problematic today, in part at least because of host switching and acceptance by D. rapae.

Host range and habitats of the aphid parasitoid Diaeretiella rapae (Hymenoptera: Aphidiidae) in Washington State.

New information is provided on the small-grain aphid parasitoids of eastern Washington—species population diversity, relative abundance, hosts, and spatial and temporal distribution across differing precipitation and cropping zones. In total 13 species of primary parasitoids were discovered attacking grain aphids: Aphelinus albipodus Hayat & Fatima, A. asychis Walker, A. varipes (Foerster), Aphidius avenaphis (Fitch), A. ervi Haliday, A. matricariae Haliday, Diaeretiella rapae (M'Intosh), Ephedrus sp., Lysiphlebus testaceipes (Cresson), Monoctonus washingtonensis Pike & Star´y, Praon unicum Smith, P. occidentale Baker, and P. yakimanum Pike & Starý. The predominant parasitoids were D. rapae on Russian wheat aphid, Diuraphis noxia (Kurdjumov); L. testaceipes on bird cherry-oat aphid, Rhopalosiphum padi (L.) and corn leaf aphid, R. maidis (Fitch); and A. avenaphis, A. ervi , and D. rapae on English grain aphid, Sitobion avenae (F.). This study provides baseline information essential for assessing future changes in aphid parasitoid species dynamics for eastern Washington. A comprehensive key to the known primary and secondary parasitoids associated with grain aphids in North America also is provided.

Small-Grain Aphid Parasitoids (Hymenoptera: Aphelinidae and Aphidiidae) of Washington: Distribution, Relative Abundance, Seasonal Occurrence, and Key to Known North American Species

In this study,we determined that 2 sampling methods (D-Vac and sweep net) taken at weekly intervals could be used to sample grasshopper species across 2 adjacent habitats of winter wheat and rangeland. We also quantified temporal density estimate shifts between winter wheat, Triticum aestivum L., and rangeland by migratory grasshoppers, Melanoplus sanguinipes (F.), twostriped grasshopper, M. bivittatus (Say), and Packard grasshopper, M. packardii Scudder, all 3 species coinhabit these areas. Specifically, at 4 study sites with the highest grasshopper densities there were significant seasonal shifts in density estimates of these species between winter wheat and rangeland suggesting that these species dispersed between habitats. At a 5th site, sweep net sampling detected a shift in density estimates between habitats by M.sanguinipes and D-Vac sampling at this site suggested there was a similar trend. At 4 study sites such shifts in density estimates did not occur suggesting that no dispersal occurred or it was not detectable at these sites using our sampling methods. In all but 1 case the density of these species, were lower than those where density estimate shifts occurred.

Sampling Method Assessment and Quantification of Temporal Shifts in Densities of Grasshopper Species (Orthoptera: Acrididae) Between Winter Wheat, Triticum aestivum, and Adjacent Rangeland

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0008347X00007677

Robert L. Gillespie

Papers

Host range and habitats of the aphid parasitoid Diaeretiella rapae (Hymenoptera: Aphidiidae) in Washington State.

Small-Grain Aphid Parasitoids (Hymenoptera: Aphelinidae and Aphidiidae) of Washington: Distribution, Relative Abundance, Seasonal Occurrence, and Key to Known North American Species

Sampling Method Assessment and Quantification of Temporal Shifts in Densities of Grasshopper Species (Orthoptera: Acrididae) Between Winter Wheat, Triticum aestivum, and Adjacent Rangeland

Comparison of age structure of three Melanoplus spp. (Orthoptera: Acrididae) in winter wheat and adjacent rangeland.