Potencial regulador de parasitoides sobre poblaciones de Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) en laboratorio, bajo condiciones semiáridas

This study aims to evaluate the regulatory potential of Lysiphlebus testaceipes and Aphidius matricariae over Aphis gossypii in semiarid laboratory conditions. Our results showed that the longevity of L. testaceipes females was significantly lower than A. matricariae ones. The daily mummification rate of aphid was more important for L. testaceipes than for A. matricariae and declined with parasitoids age. Overall, both the mummification rates and the emergence rates were the highest in L. testaceipes. A. matricariae offspring developed in a shorter time compared to L. testaceipes ones. The overall sex ratio did not vary according to parasitoid species. From our results L. testaceipes was more effective for the biological control of A. gossypii on potato in the semi-arid agro-ecosystems.Este estudio tiene como objetivo evaluar el potencial regulador de Lysiphlebus testaceipes y Aphidius matricariae sobre Aphis gossypii en condiciones de laboratorio semiáridas. Nuestros resultados mostraron que la longevidad de las hembras de L. testaceipes fue significativamente menor que la de A. matricariae. El porcentaje diario de momificación fue más importante para L. testaceipes que para A. matricariae y disminuyó con la edad de los parasitoides. En general, las tasas de momificación y de emergencia fueron más altas en L. testaceipes. La descendencia de A. matricariae se desarrolló en menos tiempo que la de L. testaceipes. La proporción sexual no varió respecto a las especies parasitoides. Con nuestros resultados, L. testaceipes fue más efectivo para el control biológico de A.&nbsp

Crop pests and predators exhibit inconsistent responses to surrounding landscape composition

The idea that noncrop habitat enhances pest control and represents a win–win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win–win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies

Les hymenopteres parasitoiedes: adaptations de l'appareil reproducteur femelle. Morphologie et ultrastructure de l'ovaire, de l'oeuf et de l'ovipositeur

SIGLEINIST T 77639 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Lutter contre les pucerons en respectant l'environnement

National audienc

Epicuticular Factors Involved In Host Recognition For The Aphid Parasitoid Aphidius Rhopalosiphi

In insect parasitoids, fitness is dependent on the host finding and recognition abilities of the female. Host recognition cues have been described for various host-parasitoid systems, but are still under investigation in aphid parasitoids. Our study aimed to clarify the respective role of physical and chemical cues in recognition of the aphid cuticle. Shed aphid exuviae were used as an elicitor in order to avoid any influence of color, movement, or volatiles present in a living aphid. We assessed the effect of chemical and heat treatments on the texture of the cuticle by using scanning electron microscopy and tested the recognition of treated cuticles by the parasitoid. We showed that recognition cues of the cuticle can be removed chemically (using combined treatments with n-hexane and methanol). Moreover, heat treatment destroyed the physical texture of the cuticle without significantly reducing parasitoid recognition. In a second step, we showed that epicuticular extracts deposited on pieces of paper triggered female attack behavior. First results concerning the chemical composition of the active extract are presented. This study shows that chemical compounds extractable by organic solvents mediate cuticle recognition by aphid parasitoids

Evaluation des régulations biologiques dans des systèmes agroécologiques

Engineering schoolLes analyses et les conclusions de ce travail d'étudiant n'engagent que la responsabilité de son auteur et non celle d'AGROCAMPUS OUEST Ce document est soumis aux conditions d'utilisation « Paternité-Pas d'Utilisation Commerciale-Pas de Modification 4

Inter-specific variation in the reactive distance in different aphid-parasitoid associations: analysis from automatic tracking of the walking path

International audienceThe distance from which hosts are perceived by foraging parasitoid females has been repeatedly considered to be an important behavioural trait that is supposed to be related to their efficiency as biological control agents. In the present study, such a ‘reactive distance’ was quantified using the automatic analysis of video-recorded females' walking paths. Inter-specific variation of this trait was analysed by comparison between Aphis gossypii Glover, Myzus persicae Sulzer, and Sitobion avenae Fabricius, and three of their parasitoid species known to present different levels of specificity to these hosts: Aphelinus abdominalis Dalman, Aphidius colemani Viereck, and Aphidius picipes Nees. Responses to two different host instars of different size were also compared in each combination. On average, parasitoid females were able to perceive aphids from a distance of about 3 to 4 mm. The only significant difference observed was between the Aphelinus and the two Aphidius parasitoid species. No difference was detected between the different host instars or species tested. Females seem to be unable to discriminate between host and non-host species from a distance. These results seem to confirm the hypothesis of the use of a cuticular contact kairomone for host recognition at the species level

The conflicting relationships between aphids and men: a review of aphid damage and control strategies.

In this review, after giving some figures on the economic impact of aphids on agricultural production, we describe the different mechanisms leading to yield losses (direct damage due to sieve drain and plant reaction, indirect damage, often the most important, due to virus transmission). Then, after a history of chemical control and of its limits, the main control strategies (chemical control with decision rules, plant resistance, biological control, farming practices) are reviewed in the light of an integrated pest management approach. Several topics tackled in this article are exemplified for cereal aphids, which are among the most important in Europe as direct feeders and virus vectors

Des pucerons et des hommes : histoire d'une relation conflictuelle

International audienc

Brassicacées et contrôle biologique : un levier suffisant pour les protéger ?

National audienc