Antoine Sanon

Mitochondrial genome sequence and expression profiling for the legume pod borer Maruca vitrata (Lepidoptera: Crambidae).

We report the assembly of the 14,054 bp near complete sequencing of the mitochondrial genome of the legume pod borer (LPB), Maruca vitrata (Lepidoptera: Crambidae), which we subsequently used to estimate divergence and relationships within the lepidopteran lineage. The arrangement and orientation of the 13 protein-coding, 2 rRNA, and 19 tRNA genes sequenced was typical of insect mitochondrial DNA sequences described to date. The sequence contained a high A+T content of 80.1% and a bias for the use of codons with A or T nucleotides in the 3rd position. Transcript mapping with midgut and salivary gland ESTs for mitochondrial genome annotation showed that translation from protein-coding genes initiates and terminates at standard mitochondrial codons, except for the coxI gene, which may start from an arginine CGA codon. The genomic copy of coxII terminates at a T nucleotide, and a proposed polyadenylation mechanism for completion of the TAA stop codon was confirmed by comparisons to EST data. EST contig data further showed that mature M. vitrata mitochondrial transcripts are monocistronic, except for bicistronic transcripts for overlapping genes nd4/nd4L and nd6/cytb, and a tricistronic transcript for atp8/atp6/coxIII. This processing of polycistronic mitochondrial transcripts adheres to the tRNA punctuated cleavage mechanism, whereby mature transcripts are cleaved only at intervening tRNA gene sequences. In contrast, the tricistronic atp8/atp6/coxIII in Drosophila is present as separate atp8/atp6 and coxIII transcripts despite the lack of an intervening tRNA. Our results indicate that mitochondrial processing mechanisms vary between arthropod species, and that it is crucial to use transcriptional information to obtain full annotation of mitochondrial genomes.

Effects of Age and Size on Anopheles gambiae s.s. Male Mosquito Mating Success

ABSTRACT Before the release of genetically-modified or sterile male mosquitoes in an attempt to control local populations of malaria vectors, it is crucial to determine male traits involved in mating success. The effects of male size and age as determinants of male mating success in Anopheles gambiae s.s. were measured in the field and under laboratory conditions in Burkina Faso. First, the body sizes (estimated by wing length) of mating, swarming, and indoor-resting male mosquitoes were compared over a 3-yr period (2006–2009) from July to October in Soumousso and Vallée du Kou, two villages in western Burkina Faso. Second, the age structure of swarming and resting male mosquitoes were characterized based on the number of spermatocysts and the proportion of sperm in the reservoir of wild-caught male testis. Third, male age effects on the insemination rate of female An. gambiae were investigated in the laboratory. The mean size of males collected in copula was significantly larger than the mean for swarming males and indoor-resting males. The optimum male age for successful insemination of females was 4–8 d. These results suggest that male size is an important trait in determining male mating competitiveness in the field. Although age was not found to be a significant factor in mating competitiveness, it was significantly correlated with swarming behaviors in the field and insemination success in the laboratory. The implications of these results in terms of sexual selection in An. gambiae and vector control programs are further discussed.

Effects of Hyptis spicigera Lam. (Labiatae) on the behaviour and development of Callosobruchus maculatus F. (Coleoptera: Bruchidae), a pest of stored cowpeas

Abstract The use of beni seed, Hyptis spicigera Lam. (Labiatae), to protect stored cowpeas from bruchid attacks is a widespread practice in West Africa. More knowledge about its actual effects on storage pests is needed to enhance its effectiveness. In this laboratory study, repellent and lethal effects of powder and essential oil from H. spicigera on Callosobruchus maculatus, the main pest of stored cowpeas, were studied. Repellency tests undertaken with a Y-tube olfactometer showed that powder was repulsive for C. maculatus adults. On the other hand, this product had no insecticidal activity. Essential oil had a dose-dependent insecticidal effect while sublethal doses repelled the adults. Both products reduced oviposition by 15 – 19 and 7 – 78% according to the doses of powder and essential oil, respectively, tested. Similarly, egg viability decreased with increasing doses of powder and essential oil used in a range of 40 – 75 and 24 – 86%, respectively. Only essential oil was lethal to C. maculatus larvae developing within cowpea seeds; however, oil activity was age-dependent, younger instars being more susceptible. These results are discussed with a view of controlling C. maculatus populations in stored cowpeas.

Influence of Hyptis suaveolens (Lamiaceae) on the Host Location Behavior of the Parasitoid Dinarmus basalis (Hymenoptera: Pteromalidae)

Abstract The solitary larval parasitoid Dinarmus basalis Rondani is a promising biological control of Callosobruchus maculatus F, a major insect pest of stored cowpeas in West Africa. Farmers traditionally introduce Hyptis suaveolens L. Poit. leaves in their granaries for protection of cowpea seeds against bruchid damage. However, effects of botanical treatment using this plant on host location behavior and reproduction of D. basalis remain unknown. Olfactometer studies showed that sublethal doses of volatiles emitted by the crushed leaves and the essential oils were repellent for naive females D. basalis, which had previously developed in the absence of H. suaveolens volatiles. These females were able to move in a three-dimensional device and to avoid the host patches associated with H. suaveolens volatiles. Their reproductive activity was consequently reduced in such patches. Females, which had been exposed to sublethal doses of H. suaveolens volatiles during their postembryonic development, were no longer repelled or only partially repelled by the plant volatiles. A habituation process may be involved in the behavior of these D. basalis females. The importance of this habituation process is discussed within the scope of the integrated protection of cowpea seeds during storage.

Seasonal and regional distribution of the cowpea pod borer Maruca vitrata (Lepidoptera: Crambidae) in Burkina Faso

Cowpea (Vigna unguiculata (L.) Walp) is an important food staple in sub-Saharan Africa. The legume pod borer Maruca vitrata Fabricius is one of the key pests of cowpea as the larvae feed on the tender parts of the stem, peduncles, flower buds, flowers and on pods of the plant, causing significant yield losses. Understanding the seasonal and geographical patterns of M. vitrata is essential for the establishment of effective pest management strategies. Sites in three ecological zones in Burkina Faso were sampled for the presence of M. vitrata adults and larvae both during and outside of the cowpea-growing season. Our data suggest that M. vitrata do not maintain a permanent population in the Sahelian or Sudano-Sahelian zones, but emigrate from the Sudanian zone where M. vitrata populations evidently may occur throughout the year.

Biotype status and resistance to neonicotinoids and carbosulfan in Bemisia tabaci (Hemiptera: Aleyrodidae) in Burkina Faso, West Africa

Bemisia tabaci Gennadius is a one of the major pests of cotton crops worldwide. In Burkina Faso, data on resistance to neonicotinoids and carbamate insecticides related to species/biotypes remain very scarce. To evaluate the resistance status of B. tabaci in Burkina Faso, four insecticides were tested using the leaf dip method on 10 field populations collected from cotton. The status of biotypes was also determined. Two biotypes, Q and ASL, were recorded. Only Q1 group was detected in Q biotype. A significant resistance to neonicotinoids and carbosulfan was shown in most of the populations tested. The highest resistance ratios (RRs) were recorded in populations from locations exhibiting only the Q1. However, the populations comprising a mix of Q1 and ASL appeared to be more susceptible to insecticides. Resistance to neonicotinoids may be related not only to the biotype status but also to the environmental factors and agricultural practices. The exclusive use of neonicotinoids against whiteflies on cotton in Burkina Faso is expected to continue to select for the resistant Q biotype and might threaten the short-term control of whitefly populations, thereby increasing the risk of outbreaks in different host plants and begomovirus transmission.

Effectiveness of spinosad (naturalytes) in controlling the cowpea storage pest, Callosobruchus maculatus (Coleoptera: Bruchidae).

ABSTRACT The biopesticide Spinosad controls many insect pests of stored-food products. Laboratory and field trials were carried out to determine the efficacy of this pesticide against the cowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), the main storage pest of cowpea, Vigna unguiculata, Walp, in West Africa. In the laboratory, Spinosad caused high mortality of adult C. maculatus and decreased the number of eggs laid by females. Spinosad, however, was less toxic in the 24 h treatment to C. maculatus than deltamethrin, an insecticide commonly used in Burkina Faso to control this insect. In “on-farm” experiments, Spinosad was effective in controlling C. maculatus. After 6 mo of storage, the number of insects emerging from cowpeas seeds was reduced by >80% by coating seeds with Spinosad but only by 43% by coating with deltamethrin. Less than 20% of the seeds were perforated in the Spinosad treatment compared with 29% for deltamethrin. Spinosad controlled C. maculatus throughout the 6 mo of cowpea storage whereas deltamethrin failed to control C. maculatus after 3 mo of storage. Spinosad has the potential to be more effective in controlling C. maculatus than deltamethrin.

First insights into the cattle serological response to tsetse salivary antigens: a promising direct biomarker of exposure to tsetse bites.

In the context of the Pan African Tsetse and Trypanosomiasis Eradication Campaign, the value of tsetse saliva antibodies as a biomarker of cattle exposure to tsetse flies was evaluated, as this could provide an alternative and complementary tool to conventional entomological methods. Serum immune reactivity to Glossina (G.) palpalis (p.) gambiensis, G. tachinoides and G. morsitans (m.) submorsitans whole saliva extracts (WSE) were monitored in cattle from both tsetse free and tsetse infested areas, and in cows experimentally exposed to tsetse flies and other hematophagous arthropods. In the tsetse infested area, cattle IgG responses to Glossina WSE were significantly higher during the dry season (p<0.0001) when herds are most exposed to tsetse flies and in infected animals (p=0.01) as expected in the case of a biomarker of exposure. Experimental studies further confirmed this as a quick rise of specific IgGs was observed in animals exposed to tsetse flies (within weeks), followed by a rapid clearance after exposure was stopped. In contrast to the two other tsetse species, G. m. submorsitans WSE enabled to detect exposure to all tsetse species and were associated with low level of cross-reactivity to other blood sucking arthropods. Finally, IgG responses to G. m. submorsitans salivary antigens enabled to distinguish different groups of cows according to exposure levels, thus indicating that tsetse saliva antibodies are not only indicators of tsetse exposure but also are correlated to the intensity of tsetse contacts (p=0.0031). Implementation of this new sero-epidemiological marker of cattle exposure to tsetse flies in the framework of tsetse elimination campaigns is discussed.

Biological control of the millet head miner Heliocheilus albipunctella in the Sahelian region by augmentative releases of the parasitoid wasp Habrobracon hebetor: effectiveness and farmers’ perceptions

On-farm augmentative releases of the parasitoid Habrobracon hebetor (Say) for controlling the millet head miner (MHM) Heliocheilus albipunctella (de Joannis) were tested in Burkina Faso, Mali and Niger from 2007 to 2009. In addition, a survey of farmers’ perceptions of insect pests, with particular focus on MHM, and the biological control program (BCP) was carried out. There was a significant increase of MHM parasitization rate after the releases, with up to 97% mortality. The survey on farmers’ perceptions revealed a fair knowledge of the MHM and the ability of farmers to describe the pest and the damage it caused. Farmers claimed that the biocontrol agent H. hebetor is effective and perceived a significant gain in grain yield due to this control strategy. Implications of these findings for a large extension of the MHM biocontrol program are discussed.

Effects of crushed fresh Cleome viscosa L. (Capparaceae) plants on the cowpea storage pest, Callosobruchus maculatus Fab. (Coleoptera: Bruchidae)

Laboratory assays were carried out to evaluate the effects of fresh Cleome viscosa on the reproduction and survival of Callosobruchus maculatus. Significant control was achieved by the two treatments with the highest quantity of crushed leaf. Fresh crushed C. viscosa also led to complete inhibition of embryonic development of eggs exposed for 48h in all botanical treatments. On-farm storage trials, using 5, 15 and 25 g C. viscosa crushed plant per 1 kg of cowpeas, showed a dose-dependent reduction in bruchid numbers of 35.4, 59.5 and 86.4%, respectively, after 120 days of storage. Moreover, the pea losses were relatively low (≤11%) and pea germination was unaffected (>80%) in all batches where C. viscosa was introduced. Our results indicate that C. viscosa has significant potential for controlling the pest. The conditions for optimal use of the plant in stored cowpea management are discussed.