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The compound N-(17- hydroxylinolenoyl)-L-glutamine (named here volicitin) was isolated from oral secretions of beet armyworm caterpillars. When applied to damaged leaves of corn seedlings, volicitin induces the seedlings to emit volatile compounds that attract parasitic wasps, natural enemies of the caterpillars. Mechanical damage of the leaves, without application of this compound, did not trigger release of the same blend of volatiles. Volicitin is a key component in a chain of chemical signals and biochemical processes that regulate tritrophic interactions among plants, insect herbivores, and natural enemies of the herbivores

The efficacy of natural enemies in controlling pests under field conditions is largely correlated with their capacity to spread within infested crops. In this study the spatial dispersal of the California red scale parasitoid Aphytis melinus was evaluated in the field after augmentative releases. The experiment was conducted in 2007 in six 1-ha plots in a Sicilian citrus orchard under integrated pest management. A total of 180,000 A. melinus adults was released in each of three plots and the other plots were left as untreated control. The flight range of the parasitoid was evaluated, for 35 days after the release, on 16 trees per each plot, located at 20 and 40 m from the central release point using yellow sticky traps activated with Aonidiella aurantii sexual pheromone and by monitoring the percentage parasitism of the scale on fruits and twigs. The effects of the distance from the release point and density of susceptible stages of host on parasitoid dispersal were evaluated. The number of wasps captured during the whole trial was greater in the traps located 20 m from the release point than in those at 40 m and in the control plots. Aphytis melinus dispersed over distances less than 40 m based on both the lower percentage parasitism and numbers captured recorded at distances of 40 m. The results are discussed in the context of the biological control of California red scale in citrus orchards by means of wasp releases. In particular, the release points should be no more than 40 m apart for a quick and homogeneous colonization of the area treated.

Parthenogenesis-inducing Wolbachia bacteria are reproductive parasites that cause infected female wasps to produce daughters without mating 1 , 2 . This manipulation of the host's reproduction enhances the transmission of Wolbachia to future generations because the bacteria are passed on vertically only from mothers to daughters. Males are dead ends for cytoplasmically inherited bacteria: they do not pass them on to their offspring. Vertical transmission of Wolbachia has been previously considered to be the main mode of transmission. Here we report frequent horizontal transmission from infected to uninfected wasp larvae sharing a common food source. The transferred Wolbachia are then vertically transmitted to the new host's offspring. This natural and unexpectedly frequent horizontal transfer of parthenogensis-inducing Wolbachia intraspecifically has important implications for the co-evolution of Wolbachia and their host.

Predator searching efficiency increases in response to a variety of environmental cues associated with its prey. The sugary excretion of aphids (honeydew) has been found to act as a prey-associated cue for many aphid natural enemies. In the present study, the honeydew excreted by Acyrthosiphon pisum (Harris) was identified as an arrestant and a contact kairomone for young larvae and adults of a common predatory hoverfly, Episyrphus balteatus (De Geer) (Diptera: Syrphidae). First and second instar larvae increased their foraging behaviour in the honeydew-treated area. When plants were sprayed with crude honeydew, the speed of movement of female E. balteatus was significantly higher than in controls, resulting in a longer period of time spent on treated plants and laying eggs. We conclude that the honeydew excreted by A. pisum induces searching behaviour and acts as and arrestant not only for adults but also for young E. balteatus larvae.

Empirical research has not supported the prediction that populations of terrestrial herbivorous arthropods are regulated solely by their natural enemies. Instead, both natural enemies (top-down effects) and resources (bottom-up effects) may play important regulatory roles. This review evaluates the hypothesis that higher-order predators may constrain the top-down control of herbivore populations. Natural enemies of herbivorous arthropods generally are not top predators within terrestrial food webs. Insect pathogens and entomopathogenic nematodes inhabiting the soil may be attacked by diverse micro- and mesofauna. Predatory and parasitic insects are attacked by their own suite of predators, parasitoids, and pathogens. The view of natural enemy ecology that has emerged from laboratory studies, where natural enemies are often isolated from all elements of the biotic community except for their hosts or prey, may be an unreliable guide to field dynamics. Experimental work suggests that interactions of biological control agents with their own natural enemies can disrupt the effective control of herbivore populations. Disruption has been observed experimentally in interactions of bacteria with bacteriophages, nematodes with nematophagous fungi, parasitoids with predators, parasitoids with hyperparasitoids, and predators with other predators. Higher-order predators have been little studied; manipulative field experiments will be especially valuable in furthering our understanding of their roles in arthropod communities.

Muga silkworm is endemic to Assam and adjoining areas in North-Eastern India, and naturally produces golden silk. From time immemorial, many ethnic and tribal groups have produced muga silk. Muga silkworms are mostly wild unlike the mulberry silkworm, which is completely domesticated. The muga silkworm is a single species with little genetic variation among populations, survives harsh climatic conditions and is subject to various diseases, pests and predators. Due to the high incidence of disease and natural enemies, and variations in climatic conditions, the production of muga silk has recently declined dramatically. In order to improve the productivity of this silkworm it is important to have a better knowledge of both its host plants and biology. Lack of knowledge of its genetics and host plants is a major bottleneck. This paper reviews various aspects of muga silkworm culture, including the availability of different populations, and methods used to select for improvement in survival, cocoon yield, disease resistance, conservation and egg production.

In response to insect feeding on the leaves, cotton (Gossypium hirsutum L.) plants release elevated levels of volatiles, which can serve as a chemical signal that attracts natural enemies of the herbivore to the damaged plant. Pulse-labeling experiments with [13C]CO2 demonstrated that many of the volatiles released, including the acyclic terpenes (E,E)-alpha-farnesene, (E)-beta-farnesene, (E)-beta-ocimene, linalool,(E)-4,8-dimethyl-1,3,7-nonatriene, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetrane, as well as the shikimate pathway product indole, are biosynthesized de novo following insect damage. However, other volatile constituents, including several cyclic terpenes, butyrates, and green leaf volatiles of the lipoxygenase pathway are released from storage or synthesized from stored intermediates. Analysis of volatiles from artificially damaged plants, with and without beet armyworm (Spodoptera exigua Hubner) oral secretions exogenously applied to the leaves, as well as volatiles from beet armyworm-damaged and -undamaged control plants, demonstrated that the application of caterpillar oral secretions increased both the production and release of several volatiles that are synthesized de novo in response to insect feeding. These results establish that the plant plays an active and dynamic role in mediating the interaction between herbivores and natural enemies of herbivores

Description du sujet. Dans le contexte actuel de réduction des risques liés à l’utilisation de produits phytosanitaires et de promotion de la biodiversité dans les milieux agricoles, il apparaît primordial d'améliorer nos connaissances sur les insectes auxiliaires qui fréquentent et se développent dans ces écosystèmes. Objectifs. Cet article vise à dresser un état des connaissances sur les auxiliaires et à mettre en lumière les principaux apports faunistiques, écologiques et fonctionnels tirés de récentes études réalisées en contexte agricole à Genève. Méthode. Les données ont été acquises de 2014 à 2019 sur plusieurs familles d'auxiliaires prédateurs et pollinisateurs dans des contextes agricoles variés (prairies extensives, vignes, vergers, cultures de colza, maraîchage) à l’aide de pièges Barber, Malaise et à émergence. Résultats. Ces travaux ont permis de récolter 48 921 données et d'inventorier 477 espèces appartenant aux grandes familles d’auxiliaires ; parmi elles, quatre espèces sont observées pour la première fois en Suisse et une cinquantaine dans le canton de Genève. Au total, 357 (± 75 %) des espèces inventoriées possèdent un stade prédateur et 103 (± 22 %) sont considérées comme de bons auxiliaires des cultures. L'utilisation de pièges à émergence a permis d'attester qu'un tiers au moins des espèces inventoriées, dont certaines rares ou menacées, peuvent compléter leur cycle de vie dans les milieux agricoles ou les utiliser comme site d'hivernation. Conclusions. Cette synthèse contribue à améliorer notre compréhension de la composition de la biodiversité des milieux agricoles qui constitue une composante non négligeable de la biodiversité en Suisse et dans les pays voisins. Elle met également en lumière le rôle des habitats semi-naturels, tels que les prairies extensives ou les interlignes des vignes, comme support pour le développement de nombreuses espèces rares et parfois menacées. Beneficial insects in agricultural landscapes: faunal, ecological and functional contributions of recent studies in the canton of Geneva (Switzerland) Description of the subject. In the context of biodiversity maintenance in agricultural environments and of risk reduction related to the use of phytosanitary products, it seems essential to improve our knowledge of the beneficial insects that develop in these ecosystems. Objectives. This article reviews the state of knowledge regarding insect auxiliaries and highlights the main faunal, ecological and functional contributions from recent studies carried out in an agricultural context in Geneva. Method. Data were collected from 2014 to 2019 on several families of predatory and pollinating auxiliaries in various agricultural contexts (extensive grasslands, vineyards, orchards, rapeseed crops, vegetable crops) using Barber, Malaise and emergence traps. Results. 48,921 individual records were collected belonging to 477 species of the main families of auxiliaries. Of these, four species were observed for the first time in Switzerland and 50 in the canton of Geneva. 357 (± 75%) of the species had a predatory stage and 103 (± 22%) could be regarded as valuable crop auxiliaries. The use of emergence traps made it possible to attest that at least a third of the species, including some rare or threatened species, are able to successfully carry out their life cycles within agricultural environments or to use them as overwintering sites. Conclusions. This review increases our understanding of the composition of the biodiversity of agricultural environments, which constitutes a significant component of biodiversity in Switzerland and in neighboring countries. It also highlights the role of semi-natural habitats as extensive grasslands or inter-rows of vineyards in supporting the development of many rare and sometimes threatened species.

The side effect of 10 insecticides, 5 fungicides and 5 herbicides on 24 different species of beneficial organisms was tested by members of the Working Group ‘Pesticides and Beneficial Organisms’ of the International Organization for Biological Control (IOBC), West Palaearctic Regional Section (WPRS). The tests were conducted by 32 members in 12 countries according to internationally approved guidelines.The microbial insecticides Bacillus thuringiensis var. kurstaki (Delfin), B. thuringiensis var. tenebrionis (Novodor) and Verticillium lecanii (Micro Germin), the fungicides cyproconazol (Alto), difenoconazol (Score), lecithin (Bioblatt Mehltau) and penconazol (Omnex), and the herbicides ethofumesat (Tramat), fluroxypyr (Starane), haloxyfop (Gallant), isoproturon (Arelon) and metamitron (Goltix) were harmless to nearly all the beneficial arthropods. The benzoylurea's teflubenzuron (Nomolt) and flufenoxuron (Cascade) affected predators such as anthocorids, earwigs, coccinellids and lacewings. The remaining preparations were more toxic and should therefore be further tested in semi-field and field experiments on relevant organisms. Most tested fungicides were toxic for the entomopathogenic fungi.

The host plants of arthropod pests may affect parasitoids and predators directly or indirectly, through multitrophic interactions. Direct plant effects may involve simple mechanisms such as reduced parasitoid searching efficiency caused by trichomes. Multitrophic effects often involve complex interactions that are not well understood, and their impact on natural enemies and biological control are difficult to predict. Knowledge of the direct and multitrophic effects creates opportunities to increase the effectiveness of natural enemies by incorporating natural enemy-enhancing traits into crop plants. The strategy may have potential for both generalist and specialist natural enemies, but the enemies' behavior and other factors will affect the results. Although combining natural enemies and plant resistance may slow the adaptation of some insect pests, it may speed up adaptations of others. A better understanding of plant/pest/natural enemy evolution is necessary to predict how to combine natural enemies and plant resistance for the best long-term results.