The potential of mini-ridging for controlling intrarow weeds: estimating minimum lethal burial depth

Weed management using synthetic herbicides is undergoing a global decline, necessitating a re-evaluation of existing control measures and the development of novel weed management tools. ‘Mini-ridging’ is a non-discriminatory, physical weeding method that functions by burying weeds in the intrarow with a laterally shifted ridge of soil. In glasshouse trials using potted plants, we found that plant recovery after soil application was influenced by plant size, which in turn was influenced by plant species, developmental stage and/or age. The likelihood of plant recovery after soil application was negatively related to the depth of soil applied: very few plants survived total coverage by soil but, conversely, survival could be substantial if some parts of the plants were not covered. The results suggest that burial under a depth of 6 cm of soil would eliminate most plants regardless of species or growth stage. Larger plants would require the application of a greater total depth of soil to achieve this 6 cm of soil cover, and weed management would, therefore, tend to be more successful and more practical if weeds were targeted when still small. This research demonstrates the potential of plant burial as a simple and reliable means of non-chemical weed management, and re-emphasises that, for weed control to be effective, the applied soil layer must cover the whole plant.     

Diversity of root-knot nematodes in Moroccan olive nurseries and orchards: does <Emphasis Type="Italic">Meloidogyne javanica</Emphasis> disperse according to invasion processes?

Background

Root-knot nematodes (RKN) are major pest of olive tree (Olea europaea ssp. europaea), especially in nurseries and high-density orchards. Soil samples were collected from main olive growing areas of Morocco, to characterize Meloidogyne species and to discuss the contribution of biotic and abiotic factors in their spatial distribution.

Results

RKN were found in 159 soil samples out of 305 from nurseries (52.1% occurrence) and in 11 out of 49 soil samples from orchards (23.2% occurrence). Biochemical and molecular characterisation (PAGE esterase and SCAR) revealed the dominance of M. javanica both in nurseries and orchards with minor presence of M. incognita only in nurseries, and M. arenaria in only one nursery. RKN were distributed on aggregated basis. Frequent presence of M. javanica in orchards might have come from nurseries. In contrast, the detection of M. incognita in nurseries alone suggests that this species could not reproduce in orchards because of either the competition with other plant-parasitic nematodes or unfit local habitats. The impact of environmental variables (climate, habitat origin and physicochemical characteristics of the substrates) on the distribution of Meloidogyne species is also discussed.

Conclusion

Olive nurseries in Morocco are not able to guarantee the safety of rooted plants. As a result, olive production systems are exposed to strong RKN invasion risks. Consequently, the use of healthy substrates in nurseries may prevent plant-parasitic nematode induction in orchards.

     

Colour and decay resistance and its relationships in Eperua grandiflora

? Eperua grandiflora, which is widely distributed in the French Guiana forest region, shows high variability in decay resistance. Further information concerning this wood quality parameter is necessary, but standard testing methods are complex and time-consuming. We assessed the use of colorimetry to determine durability in heartwood samples from a range of trees.

? Eperua grandiflora colour parameters were measured using a CIELAB system, revealing that the tree effect was greater than the radial position and height effects.

? The wood samples were exposed to Coriolus versicolor and Antrodia sp. according to two European standards (En 350-1 and XP CEN TS 15083-1). Eperua grandiflora is more susceptible to brown rot. These two standards did not give the same durability classes. The high variation in natural durability was due to the tree effect.

? These two properties were found to be correlated and the assessment also distinguished the extreme durability classes but they are not sufficient to classify the class of durability of this species.

     

Biotechnische Regulierung der Kohlmottenschildlaus in Kohlgem��se �C Sachstand und Perspektiven

The cabbage whitefly,Aleyrodes proletella, has developed to a key pest in brassica vegetable crops throughout Germany. In a 3-year project we investigated a biotechnical approach employing netting (0.8?×?0.8 mm meshsize) in combination with the native parasitoidEncarsia tricolor in an inoculative-inundative approach in organic Brussels sprouts under field conditions. In small scale plot experiments continuous netting from transplanting in May till October alone reduced whitefly larval densities by 77 % at peak infestation in all years. Remaining whitefly infestation under net was associated with the necessity of temporary net removal for the purpose of mechanical weeding, which caused primary whitefly infestation. Release of mass rearedE. tricolour under net at the first signs of larval infestation significantly increasedA. proletella-parasitation and reduced infestation compared to netted controls without release. Furthermore, at highest dosage in 2009,E. tricolor had a significant enhancing effect on raw yield and the quality level of marketable yield. Additional on-farm experiments without netting in 2008 and 2009 confirmed the control potential ofE. tricolor. Although the most important project mile stones have been achieved, namely (a)E. tricolour-establishment under net and in the open field, (b) enhanced parasitation corresponding with pest density decline and (c) a positive impact on yield and quality parameters, further research will be necessary. The focus should be on the initial infestation period, optimizing the timing, frequency and required dosage.     

Comparison between the radical scavenging activity and antioxidant activity of six distilled and nondistilled mediterranean herbs and aromatic plants

Thirty-six different extracts of six herbs and aromatic plants (fennel, common melilot, milfoil, lavandin cv. Super, spike lavender, and tarragon) were evaluated for their radical scavenging activity by the DPPH*, NBT/hypoxanthine superoxide, and *OH/luminol chemiluminescence methods, and for their antioxidant activity by the beta-carotene blenching test. The total phenolic content was also determined by the Folin-Ciocalteu method. The plant material included cultivated plants and their wastes after being distilled for essential oils. Both remarkably high phenolic content and radical scavenging activities were found for the ethyl acetate and dichloromethane fractions among the different plant extracts. In general, the distilled plant material was found to exhibit a higher phenolic content as well as antioxidant and radical scavenging activities than the nondistilled material. Ethyl acetate and dichloromethane extracts, and even some crude extract, of both distilled and nondistilled plants exhibited activities comparable to those of commercial extracts/compounds, thus making it possible to consider some of them as a potential source of antioxidants of natural origin.     

Ecology of termites from the genus <Emphasis Type="Italic">Nasutitermes</Emphasis> (Termitidae: Nasutitermitinae) and potential for science-based development of sustainable pest management programs

The genus Nasutitermes is among the most abundant wood-feeding Termitidae and an extremely diverse and heterogeneous group in terms of its biogeography and morphology. Despite the major role of several Nasutitermes species as structural pests, the phylogenetic status of this genus is still unclear, along with a confused taxonomy and species identification remaining difficult. The first aim of this review was thus to gather and discuss studies concerning the taxonomic status of the genus Nasutitermes in order to clarify this crucial point. Then, our goal was to gain new insights into the management of N. corniger, considered to be the most economically detrimental pest of this genus in South America and a Nasutitermes model species, while filtering available information concerning its biology through the prism of termite control, as well as critically examine the existing methods. We indeed strongly believe that increasing our knowledge of this species’ biological strategies is the key to progress in the challenging question of their sustainable management.     

Bacillary angiomatosis in an immunosuppressed dog

A dog being treated with immunosuppressive doses of prednisone and azathioprine for pancytopenia of unknown origin, developed, over a 2‐week period, multiple erythematous nodular lesions in the skin including footpads. Skin samples revealed lesions identical to those of human bacillary angiomatosis (BA). The nodules were composed of multifocal proliferations of capillaries, each lined by protuberant endothelial cells. The capillary clusters were separated by an oedematous connective tissue, lightly infiltrated with degenerate inflammatory cells, including neutrophils and macrophages. Tissue sections stained with Warthin–Starry silver stain revealed large numbers of positively stained bacilli in the stromal tissue, most heavily concentrated around the proliferating capillaries. Lesions of vascular degeneration and inflammation were evident. Bartonella vinsonii subsp. berkhoffii genotype 1 was independently amplified and sequenced from the blood and the skin tissue. The pathognomonic nature of the histological lesions, demonstration of compatible silver‐stained bacilli in the tissue, and identification of B. vinsonii subsp. berkhoffii in the blood and tissue indicates that this is most likely the aetiologic agent responsible for the lesions. Antibiotic therapy was successful in resolving the nodules. It would appear that B. vinsonii subsp berkhoffii, like Bartonella henselae and Bartonella quintana, has the rare ability to induce angioproliferative lesions, most likely in association with immunosuppression. The demonstration of lesions identical to those of human BA in this dog is further evidence that the full range of clinical manifestations of human Bartonella infection occurs also in canines.     

Why are wheat yields stagnating in Europe? A comprehensive data analysis for France

The last two decades are witnessing a decline in the growth trend of cereal yields in many European countries. The present study analyses yield trends in France using various sources of data: national and regional statistics, scattered trials, results of agroclimatic models using climatic data. Effects in genetic changes through breeding, agronomy and climate are investigated as possible causes. Our results show that genetic progress has not declined but it was partly counteracted, from 1990 on, by climate change which in general is unfavorable to cereal yields in temperate climates because of heat stress during grain filling and drought during stem elongation. We cannot however, from the decade beginning in 2000, rule out agronomic causes, related to policy and economy, in particular the decline of legumes in the cereal rotations, replaced by oilseed rape and to a lesser extent the decrease in nitrogen fertilization.     

Diuron mineralisation in a Mediterranean vineyard soil: impact of moisture content and temperature

BACKGROUND: The diuron‐mineralising ability of the microbiota of a Mediterranean vineyard soil exposed each year to this herbicide was measured. The impact of soil moisture and temperature on this microbial activity was assessed. RESULTS: The soil microbiota was shown to mineralise diuron. This mineralising activity was positively correlated with soil moisture content, being negligible at 5% and more than 30% at 20% soil moisture content. According to a double Gaussian model applied to fit the dataset, the optimum temperature/soil moisture conditions were 27.9 °C/19.3% for maximum mineralisation rate and 21.9 °C/18.3% for maximum percentage mineralisation. The impact of temperature and soil moisture content variations on diuron mineralisation was estimated. A simulated drought period had a suppressive effect on subsequent diuron mineralisation. This drought effect was more marked when higher temperatures were used to dry (40 °C versus 28 °C) or incubate (28 °C versus 20 °C) the soil. The diuron kinetic parameters measured after drought conditions were no longer in accordance with those estimated by the Gaussian model. CONCLUSION: Although soil microbiota can adapt to diuron mineralisation, its activity is strongly dependent on climatic conditions. It suggests that diuron is not rapidly degraded under Mediterranean climate, and that arable Mediterranean soils are likely to accumulate diuron residues. Copyright © 2010 Society of Chemical Industry