The potential benefits from cultivar specific red clover -potato crop rotations

The aim of this study was to determine if endophytic bacteria could contribute to cultivar specific interactions between red clover (Trifolium pratense L.) and potatoes (Solanum tuberosum L.) in crop rotations. Endophytic bacteria were isolated from the roots of four red clover cultivars (AC Charlie, Altaswede, Marino and Tempus) grown in the field. Populations of bacteria from each cultivar were similar. The most abundant genus was Rhizobium, but species of Curtobacterium, Pseudomonas, and Xanthomonas were common to all cultivars. Plantlets of two potato cultivars, Russet Burbank and Shepody, were inoculated individually with the seven bacterial isolates most frequently recovered from each red clover cultivar, and grown in Magenta vessels for 6 wk. Significant differences were found for plant height, and wet weights of roots, shoots and their total. Potato cultivars differed for root wet weight only, while red clover cultivar, as a source of bacteria, had a significant effect on all traits except plant height. Differences among bacteria were significant for all traits except shoot wet weight. There was a significant interaction of potato cultivar by red clover cultivar. The potato cultivar Russet Burbank did best with bacteria from the red clover cultivar, Marino; and Shepody, with bacteria from Altaswede.     

Long-term population studies and the development of an integrated management programme for control of Opuntia stricta in Kruger National Park, South Africa

1. A cactus, Opuntia stricta , has invaded almost 16 000 ha of conserved, natural habitatand has become a major weed problem in Kruger National Park (KNP), South Africa.
2. The main objectives in the control of O. stricta are to reduce the density of the weed and to curb long-range dispersal of seeds by preventing young plants from reaching the size (28 cladodes) at which they start to produce fruits.
3. Herbicides have failed to provide satisfactory control of O. stricta because the weed infestations are replenished from seeds in the soil and from small plants that are overlooked during spraying.
4. A phycitid moth, Cactoblastis cactorum , was released in KNP during 1988 in an attempt to control O. stricta biologically.
5. Population counts of the biological control agent and of the weed over a 5-year period showed that, even though C. cactorum has not provided complete control of O. stricta in KNP, the moderate levels of larval damage have stunted the growth of O. stricta and have considerably extended the time that the young plants take to reach sexual maturity.
6. Comparisons of modelled (i.e. with no C. cactorum ) and actual populations of O. stricta showed that C. cactorum is making a substantial contribution to the control of O. stricta in residual infestations of the weed that have been treated with herbicides.
7. The need for long-term evaluation studies in biological weed control is demon strated by the development of an integrated management programme for effective control of O. stricta .     

中国南方主要害虫和杂草传统生物防治的前景(英文)

中国很重视害虫生物防治,但与欧美国家相比,对更经济有效的传统生物防治重视较少。对那些源于外国、特别是最近从国外侵入的害虫来说,传统生物防治更是一本万利。本文列举了174种中国南方的有害节肢动物及它们在外国的分布和可能的发源地。还举出了分布于中国南方的6种害虫及5种杂草在外国传统生防成功的情况。     

Adsorption of Methylene Blue Dye on Pure and Carbonized Water Weeds

The influence of process variables in batch adsorption has been used to assess the removal of methylene blue dye from aqueous solution using pure and carbonized biomasses of water hyacinth and water spinach. Dried leaves of the water weeds were carbonized at temperature up to 750°C. The optimum removal of dye was achieved at pH 10, 30°C, and 55 min at a dye concentration of 10 mg/L. In an attempt to describe the adsorption process, the equilibrium isotherm for each adsorbent was determined using Langmuir and Freundlich adsorption isotherm models. Maximum adsorption capacities based on the Langmuir model for pure and carbonized water hyacinth were (mg/g) 7.05 and 2.07, respectively, whereas those of pure and carbonized water spinach were 1.25 and 5.32, respectively. It was observed that the equilibrium data were well fit by both the Freundlich and Langmuir isotherms as R ² > .97. This study demonstrates that the two waterweeds are effective, environmentally friendly, and inexpensive biomaterials for the removal of color from industrial effluents.     

Successful biological control of mist flower (Ageratina riparia) in New Zealand: Agent establishment, impact and benefits to the native flora

The white smut fungus (Entyloma ageratinae) and the gall fly (Procecidochares alani) were released in New Zealand in 1998 and 2001 respectively to suppress mist flower (Ageratina riparia). The fungus established and spread rapidly, crossing 80 km of sea to Great Barrier Island within 2 years. The mean number of P. alani galls increased exponentially to 1.96/stem at release sites, but dispersal was slow. The impact of the biocontrol agents was monitored once annually from 1998/99 to 2003/04, at up to 51 sites in the North Island. The mean percentage of live leaves infected with fungus rapidly reached nearly 60%. Maximum plant height declined significantly. In heavy infestations, mean percentage cover of mist flower declined from 81 to 1.5%. Galls were only recorded towards the end of the impact study, and at low mean numbers. As mist flower declined, the species richness and mean percentage cover of native plants increased. In contrast, the species richness and mean percentage cover of exotic plants (excluding mist flower) did not change significantly. Many plant species colonizing the plots were important native mid- or late-successional shrubs or trees. With few exceptions, the exotic plant species common in the plots were not weeds that appeared to threaten native forest habitats. There was only a weak “replacement weed effect” from the potentially serious invader African club moss (Selaginella kraussiana). These data, together with reports of reduced threats to rare endemic plants from mist flower, suggest this rapid, well-monitored weed biocontrol program was very successful.     

Sex allocation theory reveals a hidden cost of neonicotinoid exposure in a parasitoid wasp

Sex allocation theory has proved to be one the most successful theories in evolutionary ecology. However, its role in more applied aspects of ecology has been limited. Here we show how sex allocation theory helps uncover an otherwise hidden cost of neonicotinoid exposure in the parasitoid wasp Nasonia vitripennis. Female N. vitripennis allocate the sex of their offspring in line with Local Mate Competition (LMC) theory. Neonicotinoids are an economically important class of insecticides, but their deployment remains controversial, with evidence linking them to the decline of beneficial species. We demonstrate for the first time to our knowledge, that neonicotinoids disrupt the crucial reproductive behaviour of facultative sex allocation at sub-lethal, field-relevant doses in N. vitripennis. The quantitative predictions we can make from LMC theory show that females exposed to neonicotinoids are less able to allocate sex optimally and that this failure imposes a significant fitness cost. Our work highlights that understanding the ecological consequences of neonicotinoid deployment requires not just measures of mortality or even fecundity reduction among non-target species, but also measures that capture broader fitness costs, in this case offspring sex allocation. Our work also highlights new avenues for exploring how females obtain information when allocating sex under LMC.     

Organic fields sustain weed metacommunity dynamics in farmland landscapes

Agro-ecosystems constitute essential habitat for many organisms. Agricultural intensification, however, has caused a strong decline of farmland biodiversity. Organic farming (OF) is often presented as a more biodiversity-friendly practice, but the generality of the beneficial effects of OF is debated as the effects appear often species- and context-dependent, and current research has highlighted the need to quantify the relative effects of local- and landscape-scale management on farmland biodiversity. Yet very few studies have investigated the landscape-level effects of OF; that is to say, how the biodiversity of a field is affected by the presence or density of organically farmed fields in the surrounding landscape. We addressed this issue using the metacommunity framework, with weed species richness in winter wheat within an intensively farmed landscape in France as model system. Controlling for the effects of local and landscape structure, we showed that OF leads to higher local weed diversity and that the presence of OF in the landscape is associated with higher local weed biodiversity also for conventionally farmed fields, and may reach a similar biodiversity level to organic fields in field margins. Based on these results, we derive indications for improving the sustainable management of farming systems.     

Population genetic diversity of the clonal self‐incompatible herbaceous plant Linaria vulgaris along an urbanization gradient

How increasing urbanization affects biodiversity is one of the most understudied aspects of global change biology. It is, however, known that it may negatively affect plant population genetic diversity in numerous ways, for example through its negative effects on plant population size, between‐population connectivity, and reproductive success. Therefore, it is important to investigate to what extent different levels of urbanization result in these negative phenomena. Here we used microsatellite markers to investigate urbanization effects on the population genetic structure of 23 populations of the self‐incompatible, partially clonal herb Linaria vulgaris which were sampled across a gradient of urbanization. Clonal diversity as measured by the Pareto‐parameter varied between 1.11 and 2.97 and was negatively correlated to both the degree of urbanization and to population size. Urbanization and population size were not interrelated. The least clonally rich populations also experienced significantly reduced seed set. Irrespective of the degree of urbanization, L. vulgaris populations exhibited strong genetic differentiation (F_ST = 0.33) and there was no significant correlation between genetic and geographic distances, suggesting low gene flow among populations. In conclusion, we showed that urbanization negatively affected fitness of L. vulgaris populations through decreasing their clonal diversity and reproductive success, an effect that may be exacerbated by the low gene flow between populations. Although the effect was modest, the results could probably be extrapolated to bigger cities where it would be considerably more pronounced.