Recherche de la toxicité de diverses souches de Bacillus thuringiensis Berliner vis-à-vis de trois espèces de limaces

La toxicité de plusieurs préparations à base de Bacillus thuringiensis a été montrée vis-à-vis de la limace grise Deroceras reticulatum (Müller) et de l'escargot aquatique Biomphalaria alexandrina (Ehrenberg) par de précédents auteurs, laissant envisager une méthode de lutte microbiologique contre les gastéropodes. C'est pourquoi la toxicité de certains de ces produits commerciaux et de diverses souches non formulées ayant des activités insecticides différentes a été éprouvée sur trois espèces de limaces : D reticulatum, Arion distinctus Mabille et Limax valentianus Férussac et comparée à celle de produits molluscicides de référence. Parmi les produits testés, deux étaient à base de β-exotoxine (Bitoxibacillin 5 et le surnageant H1). Cependant, aucune préparation à base de Bacillus ne s'est montrée toxique vis-à-vis des trois espèces de limaces. Seuls les produits molluscicides ont confirmé leur efficacité contre les limaces.Research on the toxicity of various Bacillus thuringiensis Berliner strains to three species of slugs. Toxicity of several Bacillus thuringiensis preparations had been shown against the grey field slug Deroceras reticulatum (Müller) and the aquatic snail Biomphalaria alexandrina (Ehrenberg) by previous authors, letting view a method of microbiological control of gastropods. Therefore, the toxicities of some of these products and of several unformulated strains, having different insecticide activities, were studied on three species of slugs: D reticulatum, Arion distinctus Mabille and Limax valentianus Férussac, and compared to molluscicide products of reference. Amongst the products tested, two contained the β-exotoxin (Bitoxibacillin 5 and the surnatant H1). However, no strain of Bacillus showed to be toxic for the three slug species. Only the molluscicide products confirmed their efficiency against the slugs

Recherche de la toxicité de diverses souches de Bacillus thuringiensis Berliner vis-à-vis de trois espèces de limaces

La toxicité de plusieurs préparations à base de Bacillus thuringiensis a été montrée vis-à-vis de la limace grise Deroceras reticulatum (Müller) et de l'escargot aquatique Biomphalaria alexandrina (Ehrenberg) par de précédents auteurs, laissant envisager une méthode de lutte microbiologique contre les gastéropodes. C'est pourquoi la toxicité de certains de ces produits commerciaux et de diverses souches non formulées ayant des activités insecticides différentes a été éprouvée sur trois espèces de limaces : D reticulatum, Arion distinctus Mabille et Limax valentianus Férussac et comparée à celle de produits molluscicides de référence. Parmi les produits testés, deux étaient à base de β-exotoxine (Bitoxibacillin 5 et le surnageant H1). Cependant, aucune préparation à base de Bacillus ne s'est montrée toxique vis-à-vis des trois espèces de limaces. Seuls les produits molluscicides ont confirmé leur efficacité contre les limaces.Research on the toxicity of various Bacillus thuringiensis Berliner strains to three species of slugs. Toxicity of several Bacillus thuringiensis preparations had been shown against the grey field slug Deroceras reticulatum (Müller) and the aquatic snail Biomphalaria alexandrina (Ehrenberg) by previous authors, letting view a method of microbiological control of gastropods. Therefore, the toxicities of some of these products and of several unformulated strains, having different insecticide activities, were studied on three species of slugs: D reticulatum, Arion distinctus Mabille and Limax valentianus Férussac, and compared to molluscicide products of reference. Amongst the products tested, two contained the β-exotoxin (Bitoxibacillin 5 and the surnatant H1). However, no strain of Bacillus showed to be toxic for the three slug species. Only the molluscicide products confirmed their efficiency against the slugs

IBQS : a synthetic index of soil quality based on soil macro-invertebrate communities

We developed a synthetic index of biological soil quality (IBQS) based on soil macro-invertebrate community patterns to assess soil quality. In 22 sites representing the diversity of agroecosystems encountered in France, invertebrate communities co-varied significantly with a set of 14 parameters describing the physical and chemical properties of soil (co-inertia, p < 0.001: RV= 0.70). Using hierarchical classification, sites could be separated into four homogeneous groups and, using the 'indicator value' method, 46 indicator taxa characteristic of one or another of these groups were identified. We then used a formula that takes into account the abundance of indicator species and their respective indicator values to score soils from 1 to 20. IBQS was able to detect the effects of management practices on soil quality. Soil quality varied from 6 to 20 in forests, 7 to 9 in pastures and 2 to 9 in crops respectively. This suggests that well-managed crops and pastures may have better soil quality than some forests. Our results confirm that soil macro-invertebrates provide an integrative measure of soil quality and that the proposed index can be used either in short- or long-term monitoring, provided that it is calibrated and validated with respect to the regional context of the study

Survey of natural populations of Trichogramma (Hym., Trichogrammatidae) in the vineyards of Alsace (France)

International audienc

Crop monitoring to assess the risk of slug damage to winter wheat in the United Kingdom

The percentage of winter wheat seeds killed by slugs was measured, together with various risk factors, at 93 sites throughout the UK from 1987 to 1990. Estimates of slug populations at each site were obtained from traps baited with methiocarb pellets. The peak number of slugs trapped during the period from July until just before cultivation accounted for 26% of the variability in seed damage, more than any other single risk factor. A combined function of the number of slugs trapped at drilling and the percentage of fine soil aggregates in the seed-bed accounted for 21% of the variability in seed damage. Both (i) the peak number of slugs trapped before drilling, and (ii) the combined function of number of slugs trapped at drilling and the percentage of fine soil aggregates in the seed-bed, have potential for identifying fields with a negligible risk of slug damage to wheat seeds. However, further research is needed to improve the accuracy of forecasting slug damage. In particular, other forms of trap should be tested for their potential use in providing more accurate estimates of slug numbers and biomass at drilling, and techniques of assessing seed-bed conditions should be improved. The percentage of seedlings grazed by slugs was correlated with the numbers of slugs trapped before drilling, at drilling and after crop emergence

Biological control of slugs in winter wheat using the rhabditid nematode Phasmarhabditis-hermaphrodita

A field experiment on winter wheat in autumn 1991 investigated the effect of the rhabditid nematode, Phasmarhabditis hermaphrodita, applied to soil at five dose rates (10(8) - 10(10) infective larvae ha-1) immediately after seed sowing, on slug populations and damage to seeds and seedlings. The nematode was compared with methiocarb pellets broadcast at recommended field rate immediately after drilling and no molluscidide treatment. Slug damage to wheat seeds and seedlings was assessed 6 and 13 wk after drilling. Seedling survival increased and slug grazing damage to seedlings declined linearly with increasing log nematode dose. These two measures of slug damage were combined to give an index of undamaged plant equivalents, which also increased linearly with increasing log nematode dose. ANOVA showed that, after 6 wk, there were significantly more undamaged plant equivalents on plots treated with the two highest nematode doses (3 x 10(9) and 1 x 10(10) ha-1) than on untreated plots, but the number of undamaged plant equivalents on methiocarb-treated plots was not significantly greater than that on untreated plots. Slug populations were assessed by refuge trapping and soil sampling. Deroceras reticulatum was the commonest of several species of slugs recorded. During the first 4 wk after sowing, significantly more slugs were found under refuge traps on plots treated with certain doses of P. hermaphrodita than under traps on untreated plots and more showed signs of nematode infection than expected from the prevalence of infection in slugs from soil samples, suggesting that the presence of P. hermaphrodita altered slug behaviour. Application of P. hermaphrodita had no significant impact on numbers or biomass of slugs in soil during a 27 wk period after treatment, except after 5 wk when slug numbers were inversely related to log nematode dose. However, by this time, numbers in soil samples from untreated plots had declined to levels similar to those in plots treated with the highest dose of nematodes. During the first 5 wk after treatment, c. 20% of slugs in soil samples from untreated plots showed symptoms of nematode infection. It is suggested that this represented the background level of infection in the experimental field rather than spread of infection from treated plots. The apparent lack of impact of P. hermaphrodita on slug numbers and biomass in soil suggests that its efficacy in protecting wheat from slug damage was through inhibition of feeding by infected slugs