Synthèse bibliographique : l'écologie chimique des coccinelles

Review: chemical ecology of ladybird beetles. This paper reviews the chemical ecology of ladybird beetles (Coleoptera: Coccinellidae) to present the role of semiochemicals involved in plant-ladybird, prey-ladybird and predator-ladybird interactions. Ladybird beetles use these compounds to locate their prey, mate, protect themselves from predation or cannibalism, find a shelter to overwinter or ensure a better survival for their offspring. Thorough studies on ladybird behaviors towards these compounds could lead to their practical implementation in integrated strategies using ladybirds to control pests, like aphids or mealybugs

Technique de lombriculture au Sud Vietnam

Vermicomposting technique in South Vietnam. Earthworms play a major role in organic matter transformation. The vermicomposting allows to combine several advantages: the management of diversified organic wastes, and the production of earthworms and vermicompost. Crop residues and other plant wastes mixed with animal manure from individual farms can be used. In South Vietnam, farmers are rearing some livestock and growing a few number of crop species. From several years, an increasing number of vermicomposting units were set in many farms from the Ho Chi Minh City region. Two kinds of infrastructure materials are used: baked clay blocks or bamboo stems with plastic covers. In South Vietnam, all conditions are pooled to ensure an efficient earthworm production: suitable climate, available organic wastes and materials to build the vermicomposting structures. Both field plot fertility and protein feed for livestock (pigs, poultry, etc.) can be provided by rearing earthworms

Valorisation of a water hyacinth in vermicomposting using an epigeic earthworm Perionyx excavatus in Central Vietnam

The feasibility of vermicomposting water hyacinth (WH) [Eichhornia crassipes (Mart.) Solms] mixed with pig manure (PM) in different proportions was tested using tropical composting earthworm Perionyx excavatus. Earthworms grew and reproduced normally until the incorporation of 50% WH in initial substrate. Higher water hyacinth proportions induced earthworms' mortality and significantly affected the numbers of hatchlings and cocoons produced during vermicomposting period. The influence of the application of compost/vermicompost obtained from water hyacinth mixed with pig manure was also studied on seeds germination. Only water hyacinth substrate with 25% WH + 75% PM enhanced seeds germination for Oryza sp. and Nasturtium officinale. At the end of experiments, a significant decrease was observed in organic carbon content for each tested substrates (S1 to S8), in total nitrogen (N) for substrates containing 70% to 100% of water hyacinth (S5 to S3) and compost substrates (S1 and S2). An important decrease was also noted in total potassium for all vermicompost substrates (S3 to S8), in total magnesium for composted substrates (S1 and S2), and in C/N ratio for substrates containing 0% to 50% of water hyacinth (S8 to S6). Whereas total N in vermicompost containing 0% to 50% of water hyacinth (S8 to S6), total phosphorus, total potassium in composted substrates (S1 and S2), total magnesium in vermicompost substrates (S3 to S8) and C:N ratio in substrates containing 70% to 100% of water hyacinth (S5 to S3) expressed a significant increase after eight weeks. The result suggested that water hyacinth could be potentially useful as raw material in vermicomposting and biofertilizing if mixed with 75% of pig manure

Transcriptomic and proteomic analyses of seasonal photoperiodism in the pea aphid

<p>Abstract</p> <p>Background</p> <p>Aphid adaptation to harsh winter conditions is illustrated by an alternation of their reproductive mode. Aphids detect photoperiod shortening by sensing the length of the night and switch from viviparous parthenogenesis in spring and summer, to oviparous sexual reproduction in autumn. The photoperiodic signal is transduced from the head to the reproductive tract to change the fate of the future oocytes from mitotic diploid embryogenesis to haploid formation of gametes. This process takes place in three consecutive generations due to viviparous parthenogenesis. To understand the molecular basis of the switch in the reproductive mode, transcriptomic and proteomic approaches were used to detect significantly regulated transcripts and polypeptides in the heads of the pea aphid <it>Acyrthosiphon pisum</it>.</p> <p>Results</p> <p>The transcriptomic profiles of the heads of the first generation were slightly affected by photoperiod shortening. This suggests that trans-generation signalling between the grand-mothers and the viviparous embryos they contain is not essential. By analogy, many of the genes and some of the proteins regulated in the heads of the second generation are implicated in visual functions, photoreception and cuticle structure. The modification of the cuticle could be accompanied by a down-regulation of the <it>N</it>-β-alanyldopamine pathway and desclerotization. In <it>Drosophila</it>, modification of the insulin pathway could cause a decrease of juvenile hormones in short-day reared aphids.</p> <p>Conclusion</p> <p>This work led to the construction of hypotheses for photoperiodic regulation of the switch of the reproductive mode in aphids.</p

Impacts des vers de terre sur les composants et la dynamique du sol (synthèse bibliographique)

Impacts of earthworms on soil components and dynamics. A review. Earthworm populations are important decomposers contributing to aggregate formation and nutrient cycling processes involving nitrogen cycles, phosphorus and carbon. They are known to influence soil fertility by participating to important processes in soil such as soil structure regulation and organic matter dynamics. Earthworms also modify the microbial communities through digestion, stimulation and dispersion in casts. Consequently, changes in the activities of earthworm communities, as a result of soil management practices, can also be used as indicators of soil fertility and quality. It is therefore important to understand how earthworm communities affect soil dynamics. This review adresses the current state of knowledge on earthworm's impacts on soil structure and soil organic matter (carbon, nitrogen, and phosphorus) dynamics, with special emphasis on the effects of land management practices on earthworm communities

Does Tribolium brevicornis Cuticular Chemistry Deter Cannibalism and Predation of Pupae?

The cuticular hydrocarbons of insects are species-specific and often function as semiochemicals. The activity of Tribolium brevicornis cuticular hydrocarbons as feeding deterrents that ostensibly function to prevent pupal cannibalism and predation was evaluated. The cuticular hydrocarbons of T. brevicornis pupae were characterized and flour disk bioassays conducted with individual and combined extract components incorporated into artificial diets on which Tribolium adults fed for six days. Feeding by T. brevicornis and T. castaneum on flour disks containing cuticular extracts of T. brevicornis pupae resulted in reduced consumption and weight loss relative to feeding on control flour disks. In both cases, feeding deterrence indices exceeded 80% suggesting that T. brevicornis cuticular hydrocarbons could function to deter cannibalism and predation of pupae by larvae and adult beetles. Sixteen different cuticular hydrocarbons were identified in T. brevicornis pupal extracts. Eight of the commercially available linear alkanes were tested individually in feeding trials with eight Tribolium species. One compound (C28) significantly reduced the amount of food consumed by three species compared to control disks, whereas the compounds C25, C26, and C27 elicited increased feeding in some species. Four other compounds had no effect on consumption for any species. When four hydrocarbon mixtures were tested for synergistic deterrence on T. brevicornis and T. castaneum, none significantly influenced consumption. Our results indicate that the cuticular chemistry of T. brevicornis pupae could serve to deter predation by conspecific and congeneric beetles

Attacks by a piercing-sucking insect (Myzus persicae Sultzer) or a chewing insect (Leptinotarsa decemlineata Say) on potato plants (Solanum tuberosum L.) induce differential changes in volatile compound release and oxylipin synthesis

Plant defensive strategies bring into play blends of compounds dependent on the type of attacker and coming from different synthesis pathways. Interest in the field is mainly focused on volatile organic compounds (VOCs) and jasmonic acid (JA). By contrast, little is known about the oxidized polyunsaturated fatty acids (PUFAs), such as PUFA-hydroperoxides, PUFA-hydroxides, or PUFA-ketones. PUFA-hydroperoxides and their derivatives might be involved in stress response and show antimicrobial activities. Hydroperoxides are also precursors of JA and some volatile compounds. In this paper, the differential biochemical response of a plant against insects with distinct feeding behaviours is characterized not only in terms of VOC signature and JA profile but also in terms of their precursors synthesized through the lipoxygenase (LOX)-pathway at the early stage of the plant response. For this purpose, two leading pests of potato with distinct feeding behaviours were used: the Colorado Potato Beetle (Leptinotarsa decemlineata Say), a chewing herbivore, and the Green Peach Aphid (Myzus persicae Sulzer), a piercing-sucking insect. The volatile signatures identified clearly differ in function with the feeding behaviour of the attacker and the aphid, which causes the smaller damages, triggers the emission of a higher number of volatiles. In addition, 9-LOX products, which are usually associated with defence against pathogens, were exclusively activated by aphid attack. Furthermore, a correlation between volatiles and JA accumulation and the evolution of their precursors was determined. Finally, the role of the insect itself on the plant response after insect infestation was highlighted

Farming systems in the sandy area of the Thua Thien Hue Province, Central Vietnam, survey of socio-economic situation and constraints identified by farmers

peer reviewe