The use of herders’ accounts to map livestock activities across agropastoral landscapes in Semi-Arid Africa

Improved understandings of the agricultural and range ecologies ofsemi-arid Africa require better information on the spatiotemporal distributionof domestic livestock across agropastoral landscapes. An empirical GIS-basedapproach was developed for estimating distributions of herded livestock acrossthree agropastoral territories (around 100 km² each)over a two-year period. Algorithms developed from regression analyses of herdtracking data (with R²s 0.67) are used to transform a morecomprehensive but incomplete set of data generated from herders accounts oftheir herds grazing itineraries (400 herds following 6500 itineraries). Theresulting characterization registers 40 000 days of livestock activitiesacross694 land units (averaging 70 ha) over the study period. This studydemonstrates that rural producers knowledge of their daily extractionpracticescan be translated to fine-grained characterizations of extraction densitiesacross mixed landscapes. The spatiotemporal distribution of livestock that isrevealed by this approach diverges strongly from that predicted bycommonly-usedpoint-diffusion estimation procedures. Instead, the distribution reflects localpatterns of land use, topography, vegetation, settlements, and water points.Grazing and nongrazing times spent in land units are not spatially correlatedand the seasonality of grazing pressure is spatially variable. Therefore, theecological impacts of livestock grazing are spatially variable at fine scalesand there is a significant potential for livestock-mediated nutrient transfersacross agropastoral landscapes. The georeferenced data produced by thisapproachnot only will help evaluate the impact and sustainability of differentmanagement practices but also provides a strong empirical base for improvedspatial modeling of herded livestock.This revised version was published online in May 2005 with corrections to the Cover Date.     

DNA sequences coding for the F18 fimbriae and AIDA adhesin are localised on the same plasmid in Escherichia coli isolates from piglets

The adhesin-involved-in-diffuse-adherence (AIDA) afimbrial adhesin is produced by human, but not by animal, Escherichia coli, with the exception of German porcine verotoxigenic Escherichia coli (VTEC) [Clin. Diagn. Lab. Immunol. 8 (2001) 143]. Presence and localisation of DNA sequences (aidA) coding for and production of an AIDA adhesin were investigated in a collection of Belgian VTEC and non-VTEC E. coli isolated from piglets at weaning time. The 174 isolates were also studied by colony hybridisation for the presence of DNA sequences coding for the Stx2e verocytotoxin and the F18 fimbrial adhesin (fed): 71 were Stx2+F18+AIDA+, 26 were F18+AIDA+, 12 were AIDA+, two were Stx2+AIDA+, and one was Stx2+ only. Fifty-four of the 58 (F18+)AIDA+ isolates tested positive in a western blotting assay with an immune serum raised against the AIDA protein. Hybridisation with the AIDA gene probe on plasmid DNA profiles identified a probe-positive plasmid band in the 10 AIDA+ and in 24 of the 25 F18+AIDA+ isolates studied. Moreover in F18+AIDA+ isolates, only one plasmid band hybridised with both F18 and AIDA probes. These results confirm the presence of aidA-related genes in not only VTEC, but also non-VTEC, isolates from piglets and the production of an antigenically AIDA-related protein by the majority of probe-positive E. coli. Moreover the plasmid DNA hybridisation results suggest a localisation on the same plasmid of the aidA- and fed-related DNA sequences.     

Mechanisms of resistance to fungicides in field strains of Botrytis cinerea

Field strains of Botrytis cinerea Pers ex Fr, the causal agent of grey mould diseases, were collected from French vineyards between 1993 and 2000. Several phenotypes have been characterized according to the inhibitory effects of fungicides towards germ-tube elongation and mycelial growth. Two types of benzimidazole-resistant strains (Ben R1 and Ben R2) could be detected; negative cross-resistance to phenylcarbamates (e.g. diethofencarb) was only found in Ben R1. Benzimidazole resistance was related to point mutations at codon 198 (Ben R1) or 200 (Ben R2) of the beta-tubulin gene. Most dicarboximide-resistant strains were also weakly resistant to aromatic hydrocarbon fungicides (e.g. dicloran) but remained sensitive to phenylpyrroles (e.g. fludioxonil). These resistant field strains (Imi R1) contained a single base pair mutation at position 365 in a two-component histidine kinase gene, probably involved in the fungal osmoregulation. Three anilinopyrimidine-resistant phenotypes have been identified. In the most resistant one (Ani R1), resistance was restricted to anilinopyrimidines, but no differences were observed in the amino-acid sequences of cystathionine beta-lyase (the potential target site of these fungicides) from Ani R1 or wild-type strains. In the two other phenotypes (Ani R2 and Ani R3), resistance extended to various other groups of fungicide, including dicarboximides, phenylpyrroles and sterol biosynthesis inhibitors. This multi-drug resistance was probably determined by over-production of ATP-binding cassette transporters. The hydroxyanilide fenhexamid is a novel botryticide whose primary target site is the 3-keto reductase involved in sterol C-4 demethylations. Apart from the multi-drug-resistant strain Ani R3, three other fenhexamid-resistant phenotypes have been recognized. For two of them (Hyd R1 and Hyd R2) fenhexamid-resistance seemed to result from P450-mediated detoxification. Reduced sensitivity of the target site could be the putative resistance mechanism operating in the third resistant phenotype (Hyd R3). Increased sensitivity to inhibitors of sterol 14 alpha-demethylase recorded in Hyd R1 strains was related to two amino-acid changes at positions 15 and 105 of this enzyme.     

Toxicological and mechanistic studies on neonicotinoid cross resistance in Q-type Bemisia tabaci (Hemiptera: Aleyrodidae)

The tobacco whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) is a serious pest in numerous cropping systems and has developed a high degree of resistance against several chemical classes of insecticides. One of the latest group of insecticides introduced to the market were the neonicotinoids (chloronicotinyls), acting agonistically on insect nicotinic acetylcholine receptors. Resistance to neonicotinoid insecticides has recently been shown to occur, especially in Q-type B tabaci in some places in Almeria, Spain, whereas control of B-type B tabaci in many other intense cropping systems worldwide has remained on high levels. Our study revealed that neonicotinoid-resistant Q-type strains from Almeria were often more than 100-fold less susceptible to thiamethoxam, acetamiprid and imidacloprid when tested in discontinuous systemic laboratory bioassays. The resistance factors were generally 2- to 3-fold lower in leaf-dip bioassays. In addition to the Spanish strains, we obtained two other highly neonicotinoid-cross-resistant B tabaci greenhouse populations, one from Italy (December 1999) and one from Germany (June 2001). A molecular diagnostic analysis revealed that both strains also belong to the (Spanish) subtype Q of the B tabaci species complex. The resistance levels of Q-type whitefly strains derived from Almeria greenhouses in 1999 remained stable for at least two years, even when maintained in the laboratory without any selection pressure. The biochemical mechanisms conferring resistance to neonicotinoids have not yet been elucidated in detail, but synergist studies suggested a possible involvement of microsomal monooxygenases. Furthermore, we checked two Almerian strains of B tabaci isolated in 1998 and 1999 and demonstrated that neonicotinoid resistance is not due to an altered [3H]imidacloprid binding site of nicotinic acetylcholine receptors.     

Control and monitoring: Plum pox virus quarantine situation in France

Sharka disease caused by Plum pox virus (PPV) is present in several areas in France, and its total eradication from the territory is not considered feasible. Although sharka falls under mandatory control measures, the objective is, in the infected areas, to contain the disease in the orchards at sufficiently low levels so that the production remains economically viable. In parallel, official controls are carried out to guarantee that plants for planting, including seedlings, which are moved in trade are free from PPV.     

Effect of cultural practices on the development of arabica coffee berry disease,caused by <Emphasis Type="Italic">Colletotrichum kahawae</Emphasis>

In the high altitude regions of Africa, coffee berry disease (CBD), caused by Colletotrichum kahawae, is the main constraint for arabica coffee (Coffea arabica) production. However, certain agricultural practices can reduce losses caused by the disease and thereby promote optimum production. On small family farms in Cameroon, mixed cropping with fruit trees, intercropping with food crops and maintenance pruning of coffee trees are very widespread agricultural practices that can affect CBD epidemics. Consequently, an epidemiological study was conducted to assess how cultural practices affected the disease in an arabica coffee smallholding in Cameroon. The disease was monitored on a weekly basis over four successive years (2002–2005) on coffee trees in diverse cultural situations. Cultural practices likely to reduce losses due to CBD were identified. The infection rate was significantly lower on coffee trees grown intensively than on coffee trees grown in the traditional manner. Coffee trees located under the shade of fruit trees were significantly less attacked than those located in full sunlight. In addition, berries on the leafless parts of branches, near the main trunk of the coffee tree, were less infected than those on leafy sections. These results show that maintenance pruning, removal of mummified berries, and mixed cropping with shade plants are cultural practices which create environmental conditions that limit CBD development.     

Changes in fatty acid and sterol composition during oogenesis in the pearl oyster Pinctada margaritifera

The fatty acid and sterol composition of the oyster Pinctada margaritifera during oogenesis and in eggs was analysed. No major differences were observed during oogenesis, but the egg composition was significantly different from that of gonads. The amount of saturated fatty acids was the highest in eggs and the C16:0 predominant (P<5%); by contrast, the amount of 22:6(n‐3) was significantly lower (P<5%) than in gonads. No major differences were observed for the polar lipid (PL) composition during oogenesis. The main free sterols in gonads and eggs were cholesterol and brassicasterol. Among free sterols, the proportion of cholesterol diminished continuously from the beginning to the end of gonad maturation, and this decrease persisted in eggs after spawning. Cholesterol represented 40% to 55% of the sterol ester encountered in gonad and eggs. This study allowed us to investigate the fatty acid and sterol composition during oogenesis of the pearl oyster P. margaritifera, leading to a clearer understanding of the nutritional requirements of pearl oyster during the reproduction process.     

Einsatz der Tracermethodik zur Lokalisierung von Nestzentren lästiger Hausameisen (Lasius brunneus LATR.,Hymenoptera,Formicidae)

Summary By feeding¹³¹J mixed with a honey solution it was possible to label a colony ofLasius brunneus (LATR.) which is often a pest in buildings. Using a scintillation detector the distribution of the parts of the nest in an infested room could be determined. This was the precondition for a directed control. That method seems to be suitable also for a control ofMonomorium pharaonis (L.).