Résumé -Pour évaluer les pratiques phytosanitaires des maraîchers du Burkina Faso, des enquêtes ont été réalisées en 2015 et 2016 auprès de 316 producteurs dans les zones Ouest et Nord du pays. Seuls 9 % d'entre eux ont reçu une formation en protection des végétaux. Quatre-vingt-dix pour cent des pesticides utilisés sont achetés sur les marchés locaux sans garantie de conformité et de qualité. La lambdacyhalothrine de la famille des pyréthrinoïdes est la substance active la plus utilisée. L'utilisation sur tomate des pesticides formulés pour le coton a fortement progressé entre 2015 et 2016 (71 %). Les doses utilisées par les producteurs sont supérieures à celles recommandées. Plus de 70 % des maraîchers n'observent aucune mesure de protection adéquate depuis la préparation de la bouillie jusqu'à la fin des traitements. Le respect de délais sans traitement avant récolte dépend plus de l'état sanitaire des parcelles que des recommandations. Les contenants vides sont abandonnés sur les lieux de traitement par 53 % des répondants. Les pratiques phytosanitaires des maraîchers du Burkina Faso sont donc préoccupantes et potentiellement nuisibles pour la santé des agriculteurs et des consommateurs, et pour l'environnement.Mots clés : cultures maraîchères / tomate / pesticide / pratiques phytosanitaires / risques chimiques Abstract -Phytosanitary practices of tomato growers in Burkina Faso and risks for health and the environment. To assess the phytosanitary practices of tomato growers in Burkina Faso, surveys were carried out in 2015 and 2016 among 316 producers in the West and North zones of the country. Ninety percent of pesticides used by producers are purchased in local markets without guarantee of conformity or quality. Lambda-cyhalothrin of the pyrethroids family was the most used active substance. The use for tomato crop of cotton pesticides increased strongly between 2015 and 2016 (þ71%). The doses used by producers are higher than the recommended ones. More than 70% of the market gardeners do not observe any measure of adequate protection from the preparation of the mixture until the end of the treatments. The respect of preharvest interval depends mostly of the crop health status and does not follow the recommendations. Empty containers of pesticides are left in fields by 53% of the farmers. These results show that the phytosanitary practices of tomato producers are unsuitable and potentially harmful to the health of farmers and consumers and to the environment.

The world potato is facing major economic losses due to disease pressure and environmental concerns regarding pesticides use. This work aims at addressing these two issues by isolating indigenous bacteria that can be integrated into pest management strategies. More than 2,800 strains of Bacillus-like and Pseudomonas-like were isolated from several soils and substrates associated with potato agro-systems in Belgium. Screenings for antagonistic activities against the potato pathogens Alternaria solani, Fusarium solani (BCCM-MUCL 5492), Pectobacterium carotovorum (ATCC 15713), Phytophthora infestans (CRA-W10022) and Rhizoctonia solani (BCCM-MUCL 51929) were performed, allowing the selection of 52 Bacillus spp. and eight Pseudomonas spp. displaying growth inhibition of at least 50% under in vitro conditions, particularly against P. infestans. All 60 bacterial isolates were identified based on 16S rRNA gene sequencing and further characterized for the production of potential bio-active secondary metabolites. The antagonistic activities displayed by the selected strains indicated that versatile metabolites can be produced by the strains. For instance, the detection of genes involved bacilysin biosynthesis was correlated with the strong antagonism of Bacillus pumilus strains toward P. infestans, whereas the production of both bio-surfactants and siderophores might explain the high antagonistic activities against late blight. Greenhouse assays with potato plants were performed with the most effective strains (seven Bacillus spp. and four Pseudomonas spp.) in order to evaluate their in vivo antagonistic effect against P. infestans. Based on these results, four strains (Bacillus amyloliquefaciens 17A-B3, Bacillus subtilis 30B-B6, Pseudomonas brenneri 43R-P1 and Pseudomonas protegens 44R-P8) were retained for further evaluation of their protection index against P. infestans in a pilot field trial. Interestingly, B. subtilis 30B-B6 was shown to significantly decrease late blight severity throughout the crop season. Overall, this study showed that antagonistic indigenous soil bacteria can offer an alternative to the indiscriminate use of pesticide in potato agro-systems.

Pyrenophora tritici-repentis, the causal agent of tan spot on wheat, is a homothallic loculoascomycete with a complex race structure. The objectives of this study were to confirm the homothallic nature of the pathogen, characterize mating type diversity and toxin production genes in a global collection of strains, and analyze how these traits are associated between each other and with existing races. The pseudothecia production capacity, race identification, mating type locus (MAT), internal transcribed spacer, and glyceraldehyde-3-phosphate dehydrogenase regions were analyzed in a selection of 88 strains originating from Europe, North and South America, North Africa, and Central and South Asia. Some (60%) strains produced pseudothecia containing ascospores, independent of their origin. Race identification obtained using the multiplex polymerase chain reaction targeting host-selective toxin (HST) genes was consistent, overall, with the results based on the inoculation of a set of differential wheat cultivars and confirmed the predominance of race 1/2 strains ( approximately 83%). However, discrepancies in race identification, differences from the reference tester strains, and atypical ToxA profiles suggest the presence of new races and HSTs. The MAT1-1 and MAT1-2 coding regions are consecutively arranged in a single individual, suggesting putative heterothallic origin of P. tritici-repentis. Upstream from the MAT is an open reading frame of unknown function (ORF1) containing a MAT-specific degenerate carboxy-terminus. The phylogenetic analysis of the MAT locus reveals two distinct groups, unlinked to geographical origin or ToxA profile. Group I, the best-represented group, is associated with typical tan spot lesions caused by races 1, 2, 3, and 5 on wheat. It is more homogenous than group II encompassing race 4 strains, as well as isolates associated primarily with small spot lesions on wheat leaves or other hosts. Group II could contain several distinct taxa.

A scenario analysis in regard to the risk of chronic exposure of consumers to residues through the consumption of contaminated honey and beeswax was conducted. Twenty-two plant protection products and veterinary substances of which residues have already been detected in beeswax in Europe were selected. The potential chronic exposure was assessed by applying a worst-case scenario based on the addition of a "maximum" daily intake through the consumption of honey and beeswax to the theoretical maximum daily intake through other foodstuffs. For each residue, the total exposure was finally compared to the acceptable daily intake. It is concluded that the food consumption of honey and beeswax contaminated with these residues considered separately does not compromise the consumer's health, provided proposed action limits are met. In regard to residues of flumethrin in honey and in beeswax, "zero tolerance" should be applied.

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Fusarium culmorum is a fungal pathogen causing economically important diseases on a variety of crops. Fungicides can be applied to control this species with triazoles being the most efficient molecules. F. culmorum strains resistant to these molecules have been reported, but the underlying resistance mechanisms remain unknown. In this study, a tebuconazole-adapted F. culmorum strain was developed with a level of fitness similar to its parental strain. The adapted strain showed cross-resistance to all demethylation inhibitors (DMIs), but not to other classes of fungicides tested. RNA-Seq analysis revealed high transcriptomic differences between the resistant strain and its parental strain after tebuconazole treatment. Among these changes, FcABC1 (FCUL_06717), a pleiotropic drug resistance transporter, had a 30-fold higher expression level upon tebuconazole treatment in the adapted strains as compared to the wild-type strain. The implication of this transporter in triazole resistance was subsequently confirmed in field strains harboring distinct levels of sensitivity to triazoles. FcABC1 is present in other species/genera, including F. graminearum in which it is known to be necessary for azole resistance. No difference in FcABC1 sequences, including the surrounding regions, were found when comparing the resistant strain to the wild-type strain. Fusarium culmorum is therefore capable to adapt to triazole pressure by overexpressing a drug resistance transporter when submitted to triazoles and the same mechanism is anticipated to occur in other species.

SummaryFungi, nematodes and oomycetes belong to the most prominent eukaryotic plant pathogenic organisms. Unicellular organisms from other eukaryotic lineages, commonly addressed as protists, also infect plants. This review provides an introduction to plant pathogenic protists, including algae infecting oomycetes, and their current state of research.