Aphid sex pheromones: from discovery to commercial production

This review charts the progress made with aphid sex pheromone chemistry, from initial identification of cyclopentanoid nepetalactones, for example (4aS,7S,7aR)-nepetalactone (1). and (1R,4aS,7S,7aR)-nepetalactol (2). to commercial production from a renewable non-food crop, the catmint, Nepeta cataria (Lamiaceae). The availability of aphid sex pheromone components is now facilitating the development of new aphid pest control strategies, incorporating the use of other semiochemicals, particularly in the manipulation of populations of aphid parasitoids and aphid predators such as lacewings, which can utilise the nepetalactones and closely related molecules to locate their hosts and prey. This is the first example of a plant resource being developed as a feedstock for the production of a commercially valuable insect pheromone. The development of a plant-based production route highlights the tremendous potential that higher plants offer as cheap and renewable resources for the production of insect semiochemicals, through the wide array of secondary metabolites that they can generate.     

Comparison of Acyrthosiphon pisum (Homoptera: Aphididae) and Frankliniella occidentalis (Thysanoptera: Thripidae) as prey for the development and survival of Chrysopa pallens (Neuroptera: Chrysopidae)

The effects of two different prey species on the pre-imaginal development and survival of the green lacewing, Chrysopa pallens were determined under laboratory conditions. The developmental duration from first instar to adult emergence was shorter when larvae were fed on Acyrthosiphon pisum (22.56 ± 0.39 d) than on Frankliniella occidentalis (29 ± 0.45 d). The survival rate of lacewings from first instar to adult emergence was 22.6% higher when they were fed on A. pisum than when fed on F. occidentalis. The possible implications of these findings are applicable to mass-rearing of C. pallens and for understanding predator's biology and survival capacity in the presence of prey species evaluated and could be used in the development of an effective biological control program.     

Bayesian inferences of arthropod movements between hedgerows and orchards

Hedgerows are agro-ecological infrastructures that are assumed to enhance biodiversity in an agro-ecosystem and the control of crop pests. However, local movements of arthropod predators from hedgerows to crops remain poorly understood. In this research, these movements were analysed in eleven commercial apple orchards over two weeks in the spring of 2014. Predators were indirectly marked by spraying ovalbumin on the hedgerows. Canopy and ground predators were captured using beating and pitfall traps, respectively, in both the orchards and the hedgerows, and individuals marked by ovalbumin were detected using ELISAs. Approximately 20% of the 1272 captured predators were identified as marked. Movements between the orchards and the hedgerows of the most abundant predator taxa (Forficula auricularia, Chrysoperla sp., Philodromus spp., Cheiracanthium mildei, and Nebria brevicollis) and of four guilds (ground spiders, ground beetles, canopy spiders and canopy insects) captured across the eleven locations were estimated using a Bayesian model. On one hand, canopy insects and ground spiders were less likely to stay in the hedgerows than were the canopy spiders and ground beetles. On the other hand, the canopy spiders and ground beetles were less likely to stay in the orchard than were the canopy insects and ground spiders. However, there were exceptions within these groups: F. auricularia and N. brevicollis exhibited a high probability of staying in the hedgerow and in the orchard, respectively. Overall, these results demonstrate the frequent movements that occurred between the orchard and the adjacent hedgerow in a diverse range of predator taxa. The probabilities of movement were further affected by the characteristics of the orchard for most taxa. Therefore, agro-environmental measures that focus on hedgerow management require consideration of the local arthropod predator communities and their characteristics to enhance pest control in apple orchards.     

Fifty years later: The sequence, structure and function of lacewing cross-beta silk

Classic studies of protein structure in the 1950s and 1960s demonstrated that green lacewing egg stalk silk possesses a rare native cross-beta sheet conformation. We have identified and sequenced the silk genes expressed by adult females of a green lacewing species. The two encoded silk proteins are 109 and 67 kDa in size and rich in serine, glycine and alanine. Over 70% of each protein sequence consists of highly repetitive regions with 16-residue periodicity. The repetitive sequences can be fitted to an elegant cross-beta sheet structural model with protein chains folded into regular 8-residue long beta strands. This model is supported by wide-angle X-ray scattering data and tensile testing from both our work and the original papers. We suggest that the silk proteins assemble into stacked beta sheet crystallites bound together by a network of cystine cross-links. This hierarchical structure gives the lacewing silk high lateral stiffness nearly threefold that of silkworm silk, enabling the egg stalks to effectively suspend eggs and protect them from predators.