A. Nicholas E. Birch

Tri-trophic interactions involving pest aphids, predatory 2-spot ladybirds and transgenic potatoes expressing snowdrop lectin for aphid resistance

Transgenic crops genetically engineered for enhanced insect resistance should be compatible with other components of IPM for the pest resistance to be durable and effective. An experimental potato line was genetically engineered to express an anti-aphid plant protein (snowdrop lectin, GNA), and assessed for possible interactions of the insect resistance gene with a beneficial pest predator. These extended laboratory studies are the first to demonstrate adverse tri-trophic interactions involving a lectin- expressing transgenic crop, a target pest aphid and a beneficial aphidophagous predator. When adult 2-spot ladybirds (Adalia bipunctata[L.]) were fed for 12 days on peach-potato aphids (Myzus persicae Sulzer) colonising transgenic potatoes expressing GNA in leaves, ladybird fecundity, egg viability and longevity significantly decreased over the following 2–3 weeks. No acute toxicity due to the transgenic plants was observed, although female ladybird longevity was reduced by up to 51%. Adverse effects on ladybird reproduction, caused by eating peach-potato aphids from transgenic potatoes, were reversed after switching ladybirds to feeding on pea aphids from non-transgenic bean plants. These results demonstrate that expression of a lectin gene for insect resistance in a transgenic potato line can cause adverse effects to a predatory ladybird via aphids in its food chain. The significance of these potential ecological risks under field conditions need to be further evaluated.

How agro-ecological research helps to address food security issues under new IPM and pesticide reduction policies for global crop production systems

Drivers behind food security and crop protection issues are discussed in relation to food losses caused by pests. Pests globally consume food estimated to feed an additional one billion people. Key drivers include rapid human population increase, climate change, loss of beneficial on-farm biodiversity, reduction in per capita cropped land, water shortages, and EU pesticide withdrawals under policies relating to 91/414 EEC. IPM (Integrated Pest Management) will be compulsory for all EU agriculture by 2014 and is also being widely adopted globally. IPM offers a toolbox of complementary crop- and region-specific crop protection solutions to address these rising pressures. IPM aims for more sustainable solutions by using complementary technologies. The applied research challenge now is to reduce selection pressure on single solution strategies, by creating additive/synergistic interactions between IPM components. IPM is compatible with organic, conventional, and GM cropping systems and is flexible, allowing regional fine-tuning. It reduces pests below economic thresholds utilizing key ecological services, particularly biocontrol. A recent global review demonstrates that IPM can reduce pesticide use and increase yields of most of the major crops studied. Landscape scale ecological engineering, together with genetic improvement of new crop varieties, will enhance the durability of pest-resistant cultivars (conventional and GM). IPM will also promote compatibility with semiochemicals, biopesticides, precision pest monitoring tools, and rapid diagnostics. These combined strategies are urgently needed and are best achieved via multi-disciplinary research, including complex spatio-temporal modelling at farm and landscape scales. Integrative and synergistic use of existing and new IPM technologies will help meet future food production needs more sustainably in developed and developing countries, in an era of reduced pesticide availability. Current IPM research gaps are identified and discussed.

Identification of glucosinolates on the leaf surface of plants from the Cruciferae and other closely related species.

Leaf-surface extracts prepared from 18 non-cultivated (wild) plant species, derived from the Capparidaceae, Cruciferae, Resedaceae and Tropaeolaceae were ranked for their ability to stimulate oviposition by the cabbage root fly, and analysed for glucosinolates. A total of 28 different glucosinolates were identified. A clear relationship was detected between the indolyl-, benzyl- and the total glucosinolate composition on the leaf surface and oviposition preference by cabbage root fly females. However, as the results are not fully explained by differences in leaf surface glucosinolates, other important oviposition deterrents and stimuli on the leaf surface of these wild crucifers must also be present.

Concanavalin A inhibits development of tomato moth (Lacanobia oleracea) and peach-potato aphid (Myzus persicae) when expressed in transgenic potato plants

The effects of concanavalin A (ConA), a glucose/mannose-specific lectin from jackbean (Canavalia ensiformis), on insect crop pests from two different orders, Lepidoptera and Homoptera, were investigated. When fed to larvae of tomato moth (Lacanobia oleracea) at a range of concentrations (0.02–2.0% of total protein) in artificial diet, ConA decreased survival, with up to 90% mortality observed at the highest dose level, and retarded development, but had only a small effect on larval weight. When fed to peach-potato aphids (Myzus persicae) at a range of concentrations (1–9μM) in liquid artificial diet, ConA reduced aphid size by up to 30%, retarded development to maturity, and reduced fecundity (production of offspring) by >35%, but had little effect on survival. With both insects, there was a poor correlation between lectin dose and the quantitative effect. Constitutive expression of ConA in transgenic potatoes driven by the CaMV 35S promoter resulted in the protein accumulating to levels lower than predicted, possibly due to potato not being able to adequately reproduce the post-translational processing of this lectin which occurs in jackbean. However, the expressed lectin was functionally active as a haemagglutinin. Bioassay of L.xa0oleracea larvae on ConA-expressing potato plants showed that the lectin retarded larval development, and decreased larval weights by >45%, but had no significant effect on survival. It also decreased consumption of plant tissue by the larvae. In agreement with the diet bioassay results, ConA-expressing potatoes decreased the fecundity of M.xa0persicae by up to 45%. ConA thus has potential as a protective agent against insect pests in transgenic crops.

Eight principles of integrated pest management

The use of pesticides made it possible to increase yields, simplify cropping systems, and forego more complicated crop protection strategies. Over-reliance on chemical control, however, is associated with contamination of ecosystems and undesirable health effects. The future of crop production is now also threatened by emergence of pest resistance and declining availability of active substances. There is therefore a need to design cropping systems less dependent on synthetic pesticides. Consequently, the European Union requires the application of eight principles (P) of Integrated Pest Management that fit within sustainable farm management. Here, we propose to farmers, advisors, and researchers a dynamic and flexible approach that accounts for the diversity of farming situations and the complexities of agroecosystems and that can improve the resilience of cropping systems and our capacity to adapt crop protection to local realities. For each principle (P), we suggest that (P1) the design of inherently robust cropping systems using a combination of agronomic levers is key to prevention. (P2) Local availability of monitoring, warning, and forecasting systems is a reality to contend with. (P3) The decision-making process can integrate cropping system factors to develop longer-term strategies. (P4) The combination of non-chemical methods that may be individually less efficient than pesticides can generate valuable synergies. (P5) Development of new biological agents and products and the use of existing databases offer options for the selection of products minimizing impact on health, the environment, and biological regulation of pests. (P6) Reduced pesticide use can be effectively combined with other tactics. (P7) Addressing the root causes of pesticide resistance is the best way to find sustainable crop protection solutions. And (P8) integration of multi-season effects and trade-offs in evaluation criteria will help develop sustainable solutions.

The ‘mother knows best’ principle: should soil insects be included in the preference–performance debate?

Abstract 1.u2002Few entomological studies include soil‐dwelling insects in mainstream ecological theory, for example the preference–performance debate. The preference–performance hypothesis predicts that when insect herbivores have offspring with limited capacity to relocate in relation to a host plant, there is a strong selection pressure for the adult to oviposit on plants that will maximise offspring performance.

A comparison of the composition of epicuticular wax from red raspberry (Rubus idaeus L.) and hawthorn (Crataegus monogyna Jacq.) flowers.

Epicuticular waxes have been characterised from the flowers of raspberry and hawthorn, on both of which adult raspberry beetles (Byturus tomentosus) can feed. The flower wax from both species had similar alkane profiles and also contained long-chain alcohols, aldehydes and fatty acids. The range of the carbon numbers detected for these classes of compounds was broadly similar in both but the relative amounts of each differed between species. Raspberry flower wax also contained fatty acid methyl esters, a group of compounds that has rarely been detected in plant epicuticular waxes, however, these were not observed in hawthorn flower wax. Long-chain alcohol-fatty acid esters with carbon numbers ranging from C36 to C48 were also detected in both plant species. However, an examination of their constituent acids indicated that in hawthorn the esters based on the C16 fatty acid predominated, whilst in raspberry flower wax, esters based on the C20 fatty acid were most abundant. Both species also contained pentacyclic triterpenoids, which accounted for, on average, over 16 and 48% of the total wax extracted from raspberry and hawthorn flowers respectively. In the former, ursolic and oleanolic acids accounted for over 90% of the pentacyclic triterpenes, whilst hawthorn flower wax, in addition to containing these acids, also contained high relative concentrations of both free and esterified alpha- and beta-amyrins.

Combining plant resistance and a natural enemy to control Amphorophora idaei

The European large raspberry aphid Amphorophora idaei Börner (Homoptera: Aphididae) is a virus vector of at least four plant virus complexes making it the most important aphid pest of raspberries in Northern Europe. An approach combining a bottom-up control (plant resistance) and a top-down control (an aphid parasitoid) using Aphidius ervi Haliday (Hymenoptera: Aphidiinae) was investigated in the laboratory. Aphid performance (pre-reproductive period, total reproductive output, lifespan and rm) were compared when reared on both a susceptible cultivar and a resistant cultivar with significantly poorer performance on the resistant cultivar. Parasitoid attack behaviour increased with aphid density on both cultivars, but was significantly lower on resistant plants than susceptible plants. Aphids showed a greater tendency to drop from the plant when feeding on resistant plants compared with susceptible plants. The significance of the results is discussed in the context of possible control of the aphid using these combined methods.

REVIEW: A mechanistic framework to improve understanding and applications of push‐pull systems in pest management

Summary n n nPush-pull or stimulo-deterrent cropping systems combine a trap crop or other attractant or arrestant stimulus distant from the crop and a deterrent or repellent near or within the target crop, to divert pests, reducing their populations on the target crop. Although the concept is decades old, there are few successful applications in pest management. nIn this article, we address this shortcoming by offering a mechanistic conceptual framework of push-pull systems, based on the cues, sensory modalities, pest behaviours and spatial ranges over which they can occur during host selection and that can influence pest distribution. nWe review published work on push-pull systems in the light of this framework, finding that the literature tends to focus on longer-range stimulo-deterrence strategies rather than the full range of cues involved and modalities that can come into play, with imperfect understanding of cues involved in most systems. nThe imbalance in research emphasis and incomplete understanding of push-pull mechanisms suggest opportunities to improve and broaden the palette of potential push-pull technologies. nThe framework also helps clarify other aspects important for achieving success with push-pull methods, including the role of synergy, deployment geometry, intraspecific variability and the wider arthropod community in these systems. nSynthesis and applications. A conceptual and mechanistic framework is provided for the development of push-pull or stimulo-deterrent pest management approaches. This framework informs a proposed research agenda for designing push-pull technologies. That agenda involves including all cues and modalities, exploiting synergies, tuning deployment geometry in accordance with these factors. It also considers pest and crop dynamics and the arthropod community of the system. The framework can benefit managers by helping them to consider more fully the behaviour of the target pests when creating crop and non-crop geometries to achieve push-pull benefits. Research-based push-pull systems will be better implemented and modified by producers if they understand how insects respond to sources of push and pull in the system, allowing effective monitoring and fine-tuning to increase effectiveness of this specialized component of integrated pest management.

Study of anatomical changes in Coccinella septempunctata (Coleoptera: Coccinellidae) induced by diet and by infection with the larva of Dinocampus coccinellae (Hymenoptera: Braconidae) using magnetic resonance microimaging

A range of nuclear magnetic resonance (NMR) techniques, 1 H liquid spectroscopy and T1 and T2 relaxation measurements, and microimaging, have been used to observe changes taking place within the bodies of live samples of Coccinella septempunctata, under a variety of conditions. NMR measurements showed that various organs could be seen and identified. It also showed that by changing the diet of the ladybird from aphids (Acyrthosiphon pisum (Harris)) to a standard artificial diet, major changes took place in the insects tissues. By using a combination of all three techniques it was concluded that on changing the diet of C. septempunctata a mass of nutrient was built up within the insects abdomen possibly in the same manner as happens before diapause. Changes in the response to NMR measurements were also seen after infection of C. septempunctata by the parasitoid wasp (Dinocampus coccinellae). Most significantly an image of the parasitoid larva could be seen within the body mass of the ladybird. It was con- cluded that NMR could become a major tool in the non-destructive study of insects not just as a means of studying anatomy but also to observe changes in the nature of body tissue.