Improving control of duponchelia fovealis (Lepidoptera: Pyralidae) by rooting media related strategies

Soil-dwelling predatory mites can be very effective as biological control agents against larvae of the lepidopteral pest Duponchelia fovealis. Some growing media were reported to have natural high level and stable populations of predatory mite. The objective of this experiment was to define conditions to establish stable predatory mite populations in the rooting medium and to assess the direct effect of the rooting media on pest development. Eight rooting media were prepared, including a range of degradabilities as measured with the Oxygen Uptake Rate method (OUR). The OUR range was created by mixing peat products, coir dust, bark, perlite, compost and wood fiber. Each treatment was split: half with and half without a commercially used mulch to create a drier top layer. Kalanchoës were grown on these rooting media. After one week soil-dwelling predatory mites (Hypoaspis miles) were added. Adults of the pest Duponchelia fovealis were released during a number of weeks. Both populations were counted. Results show that the OUR range was successfully achieved. The commercial mulch, a cork based fine granulate, reduced the numbers of Duponchelia by 32%. The number of predatory mites was related to the oxygen uptake of the rooting media (R2=0.87). The predatory mite reduced the numbers of Duponchelia larvae on average by 58%. Thus, biological control by soil-dwelling predatory mites can be improved by offering rooting media with an increased degradability as measured by the oxygen uptake rate. The combined effects of using predatory mite and mulch layers are discussed

Combining lacewings and parasitoids for biological control of foxglove aphids in sweet pepper

The role of natural enemy diversity in biological pest control has been debated in many studies, and understanding how interactions amongst predators and parasitoids affect herbivore populations is crucial for pest management. In this study, we assessed the individual and combined use of two species of natural enemies, the parasitoid Aphidius ervi Haliday, and the predatory brown lacewing Micromus variegatus (Fabricius), on their shared prey, the foxglove aphid, Aulacorthum solani (Kaltenbach), on sweet pepper. We hypothesized that the presence of intraguild predation (IGP) and predator facilitation (through induced aphid dropping behaviour) might have both negative and positive effects on aphid control, respectively. Our greenhouse trial showed that overall, the greatest suppression of aphids occurred in the treatment with both the parasitoid and the lacewing. While the combination of lacewings and parasitoids significantly increased aphid control compared to the use of parasitoids alone, the effect was not significantly different to the treatment with only predators, although there was a clear trend of enhanced suppression. Thus, the combined effects of both species of natural enemies were between additive and non-additive, suggesting that the combination is neither positive nor negative for aphid control. High levels of IGP, as proven in the laboratory, were probably compensated for by the strong aphid suppression provided by the lacewings, whether or not supplemented with some level of predator facilitation. For aphid management over a longer time scale, it might still be useful to combine lacewings and parasitoids to ensure stable and resilient aphid control.Fil: Rocca, Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Messelink, Gerben J.. University of Agriculture Wageningen; Países Bajo

Generalist predator Stratiolaelaps scimitus hampers establishment of the bulb scale mite predator Neoseiulus barkeri in Hippeastrum

In this study we investigate the hypothesis that presence of the generalistsoil-dwelling predatory mite Stratiolaelaps scimitus (Womersley)results in lower densities of the phytoseiid soil-dwelling predatorNeoseiulus barkeri Hughes in Hippeastrum (amaryllis). If true, thismay increase risks of bulb scale mite Steneotarsonemus laticeps (Halbert)infestations in Hippeastrum, because N. barkeri predates on this pest,whereas S. scimitus does not. In a greenhouse trial we show indeed thatthe release of S. scimitus results in significantly lower densities of N.barkeri in a Hippeastrum crop. Moreover, analyses of soil and bulbsamples from a commercial Hippeastrum farm suggest that this predatorinterference is facilitated by soil cooling techniques that drive thepredators together to small ‘islands’ of higher surface temperature

On-site residence time in a driven diffusive system: violation and recovery of mean-field

We investigate simple one-dimensional driven diffusive systems with open boundaries. We are interested in the average on-site residence time defined as the time a particle spends on a given site before moving on to the next site. Using mean-field theory, we obtain an analytical expression for the on-site residence times. By comparing the analytic predictions with numerics, we demonstrate that the mean-field significantly underestimates the residence time due to the neglect of time correlations in the local density of particles. The temporal correlations are particularly long-lived near the average shock position, where the density changes abruptly from low to high. By using Domain wall theory (DWT), we obtain highly accurate estimates of the residence time for different boundary conditions. We apply our analytical approach to residence times in a totally asymmetric exclusion process (TASEP), TASEP coupled to Langmuir kinetics (TASEP + LK), and TASEP coupled to mutually interactive LK (TASEP + MILK). The high accuracy of our predictions is verified by comparing these with detailed Monte Carlo simulations

Robuuste bladluisbestrijding: een stappenplan

Jaarlijks veroorzaken bladluizen schade aan gewassen. Naast zuigschade aan de planten, vervuilen kolonies luizen het gewas en de vruchten. Om dit te voorkomen zijn preventieve en curatieve maatregelen noodzakelijk. De juiste groeiomstandigheden en ontwikkelingskansen voor de biologische bestrijders creëren de voorwaarden. Het is niet voldoende om alleen maar biologische bestrijders in te brengen; natuurlijke vijanden vormen samen met de plaagorganismen een voedselweb waarbinnen allerlei interacties optreden. Dit beïnvloedt het resultaat van de bestrijding. In dit bioKennisbericht vindt u stapsgewijs aandachtspunten en aanwijzingen voor de beheersing van bladluizen in paprika