Banker plants increase biological pest control by supporting populations of non-pest arthropod species, used as alternative hosts or prey by natural enemies. Due to the specificity of trophic interactions, banker plants may not efficiently promote natural enemies with different ecologies. Yet in most cropping systems, different pest species are present together and require different biocontrol agents to efficiently control them. In the present study, we tested the combined use of two banker plants and their associated prey/host to enhance populations of the specialist parasitoid Encarsia formosa targeting the main tomato pest Bemisia tabaci, and a polyphagous ladybird Propylea japonica targeting the secondary pest Myzus persicae in tomato crops. In a laboratory and a greenhouse experiment, we measured the abundances of these four species using the Ricinus communis—Trialeurodes ricini banker plant system alone, in combination with the Glycines max—Megoura japonica system, or in absence of banker plants. We found that the first banker plant system enhanced populations of E. formosa, resulting in increased suppression of B. tabaci populations and the suppression of their outbreak in both our laboratory and greenhouse experiment. Conversely, abundances of P. japonica were not affected by this first system, but were significantly increased when the second was present. This resulted in increased control of M. persicae populations and the suppression of their early and late outbreaks. Our study demonstrates the potential for combined banker plants to provide long-term, sustainable control of multiple pests by their target natural enemies in complex agroecosystems.
This article reports on a facile route for the preparation of polypyrrole nanospheres with improved water solubility, ordering and conductivity in the presence of a polyelectrolyte, such as phosphorylated polyvinyl alcohol. The phosphorylated polyvinyl alcohol (PPVA) was used as both the stabilizer and the dopant in the chemical oxidative polymerization of pyrrole. The resulting PPVA doped polypyrrole (PPy) nanocomposites (PPy-PPVA) were characterized with FTIR, TGA, SEM and AFM techniques. The electrical conductivity of polymer was measured by four-point probe method. Our observation and results suggest a plausible formation mechanism of PPy nanospheres, PPVA micelle might have functioned as ‘template’ during the polymerization of pyrrole monomers, meanwhile, the PPy chains doped with phosphate group. It was found that the size decreased and their dispersion stability in water increased with the increasing feeding ratio of PPVA. The conductivity of PPy with different morphologies was also measured and compared. When the PPVA: pyrrole feeding ratio ranged from 20 to 50 wt%, the PPy-PPVA nanoparticles showed spherical shape with excellent uniformity, good electrical conductivity (up to 33.1 S·cm?1), and weakly temperature dependent conductivity. It’s worth mentioning that the PPy-PPVA nanocomposite prepared in high PPVA feeding ratio has been well-dispersed for more than 24 months, which indicates its significant dispersion stability. 相似文献
This study investigated the maturity and gaseous emissions from vermicomposing with agricultural waste. A vermicomposting treatment (inoculated Eisenia fetida) was conducted over a 50-day period, taking tomato stems as the processing object and using cow dung as the nutrient substrate. A thermophilic composting treatment without earthworm inoculation was operated as a control treatment. During the experiment, maturity indexes such as temperature, pH, C/N ratio, and germination index (GI) were determined and continuous measurements of earthworm biomass and CH4, N2O, and NH3 emissions were carried out. The results showed that the temperature during vermicomposting was suitable for earthworm survival, and the earthworm biomass increased from 10.0 to 63.1 kg m?3. Vermicomposting took less time on average to reach the compost maturity standard (GI 80%), and reached a higher GI (132%) in the compost product compared with the thermophilic composting treatment. Moreover, the decrease of the C/N ratio in vermicompost indicated stabilization of the waste. The activities of earthworms played a positive role in reducing gaseous emissions in vermicompost, resulting in less emissions of NH3 (12.3% NH3-N of initial nitrogen) and total greenhouse gases (8.1 kg CO2-eq/t DM) than those from thermophilic compost (24.9% NH3-N of initial nitrogen, 22.8 kg CO2-eq/t DM). Therefore, it can be concluded that vermicomposting can shorten the period required to reach compost maturity, can obtain better maturity compost, and at the same time reduce gaseous emissions. As an added advantage, the earthworms after processing could have commercial uses. 相似文献
