No abstract

The bird‐cherry oat aphid (Rhopalosiphum padi) is a global pest, attacking most cereal crops including barley, wheat, oats and triticale. The aphids cause yield losses through direct feeding damage and the transmission of plant viruses. In Australia, feeding injury can reduce cereal yields by 6%, with the damage caused by aphid‐vectored viruses reducing the yield of cereal crops by up to 30%. Aphid control in these crops is achieved almost exclusively with insecticides, and there is growing concern surrounding insecticide resistance evolution in multiple aphid species. In this study, nine field populations of R. padi were collected from localities representing the major grain growing regions of Australia. Toxicity data against four insecticides (dimethoate, alpha‐cypermethrin, pirimicarb and imidacloprid) was generated for each aphid population. This revealed little differences in population responses for three of these insecticides. For alpha‐cypermethrin, a widely used insecticide in Australia, there were significant differences between several populations. These data will be important for future monitoring of insecticide responses of R. padi and highlight the impending pest management challenges growers could encounter in Australia.

We examined the hypothesis that the polyphagous green peach aphid (Myzus persicae) shows clone-specific adaptation to the narrow-leafed lupin (Lupinus angustifolius) containing toxic quinolizidine alkaloids. We compared the performance of a lupin-feeding clone of M. persicae from Western Australia to that of nine clones of the same species collected from eastern Australian locations, where narrow-leafed lupins rarely occur. Mean relative growth rate (MRGR) and colonization ability varied among the M. persicae clones on one aphid-susceptible and two aphid-resistant lupin varieties. The performance of the lupin-feeding clone was better than that of all other clones on the resistant narrow-leafed lupin varieties "Tanjil" and "Kalya", indicating that successful lupin feeding is not a characteristic of the species. Gas chromatography-mass spectrometry analyses (GC-MS) of phloem from the different lupin varieties detected differences in the quantities of two alkaloid compounds identified as 13-OH-lupanine and lupanine. The lupin-feeding M. persicae clone also showed better performance on artificial diet amended with lupanine. The results suggest that the M. persicae clone collected from Western Australia is adapted to feed successfully on narrow-leafed lupin, and that this adaptation may involve improved tolerance of lupanine in its diet.

Experiments were conducted to investigate the potential induction of plant defenses by Myzus persicae Sulzer (Homoptera: Aphididae) feeding on five lupin, Lupinus spp. (Leguminosae), varieties with well‐characterized levels of aphid resistance. Myzus persicae feeding on L. angustifolius and L. luteus varieties induced genotype‐specific changes in their host that were not consistent with the level of aphid resistance or the plant species. The plant responses were systemically detected by apterous and alate forms of the aphids. Chemical assays revealed no induction of oxidizing enzyme (catalase, peroxidase, or polyphenol oxidase) activity, serine or cystein proteinase inhibitors, or soluble phenolics in any of the five varieties tested following 3 days of feeding by 10 or 30 aphids. However, there were significant differences among the five lupin varieties in the levels of peroxidase and polyphenol oxidase activity, proteinase inhibitors, and soluble phenolics.

Aphids are important agricultural pests causing major yield losses worldwide. Since aphids can rapidly develop resistance to chemical insecticides there is an urgent need to find alternative aphid pest management strategies. Despite the economic importance of bluegreen aphid (Acyrthosiphon kondoi), very few genetic resources are available to expand our current understanding and help find viable control solutions. An artificial diet is a desirable non-invasive tool to enable the functional characterisation of genes in bluegreen aphid and discover candidate target genes for future use in RNA interference (RNAi) mediated crop protection against aphids. To date no artificial diet has been developed for bluegreen aphid, so we set out to develop a suitable diet by testing and optimising existing diets. Here, we describe an artificial diet for rearing bluegreen aphid and also provide a proof of concept for the supplementation of the diet with RNAi molecules targeting the salivary gland transcript C002 and gap gene hunchback, resulting in bluegreen aphid mortality which has not yet been documented in this species. Managing this pest, for example via RNAi delivery through artificial feeding will be a major improvement to test bluegreen aphid candidate target genes for future pest control and gain significant insights into bluegreen aphid gene function.