Karamoko Diarra

Tuta absoluta Meyrick (Lepidoptera: Gelechiidae): a new threat to tomato production in sub-Saharan Africa

In sub-SaharanAfrica, vegetable crops are an essential component of sustainable development, with a significant contribution to food security and nutritional balance, but also an important source of income for resource-poor growers, especially in urban and peri-urban areas (FAO 2012). However, a major constraint to growing field horticultural crops is the reduction in yield and quality caused by insect pests by direct feeding or as plant disease vectors (James et al. 2010; Ekesi et al. 2011). Chemical control is the main control strategy implemented by growers to cope with insect pests (Ngowi et al. 2007; Grzywacz et al. 2010). Extensive and sometimes inappropriate use of chemical insecticides to control insect pests increases production costs and negatively impacts food safety (residues), human health and environment, especially biodiversity and beneficial arthropods (Desneux et al. 2007; Biondi et al. 2012). The implementation of effective and ecologically-sound integrated pest management (IPM) strategies is needed to develop sustainable vegetable production.

Ecology of Phlebotomine Sand Flies in the Rural Community of Mont Rolland (Thiès Region, Senegal): Area of Transmission of Canine Leishmaniasis

Background Different epidemiological studies previously indicated that canine leishmaniasis is present in the region of Thiès (Senegal). However, the risks to human health, the transmission cycle and particularly the implicated vectors are unknown. Methodology/Principal Findings To improve our knowledge on the population of phlebotomine sand flies and the potential vectors of canine leishmaniasis, sand flies were collected using sticky traps, light traps and indoor spraying method using pyrethroid insecticides in 16 villages of the rural community of Mont Rolland (Thiès region) between March and July 2005. The 3788 phlebotomine sand flies we collected (2044 males, 1744 females) were distributed among 9 species of which 2 belonged to the genus Phlebotomus: P. duboscqi (vector of cutaneous leishmaniasis in Senegal) and P. rodhaini. The other species belonged to the genus Sergentomyia: S. adleri, S. clydei, S. antennata, S. buxtoni, S. dubia, S. schwetzi and S. magna. The number of individuals and the species composition differed according to the type of trap, suggesting variable, species-related degrees of endophily or exophily. The two species of the genus Phlebotomus were markedly under-represented in comparison to the species of the genus Sergentomyia. This study also shows a heterogeneous spatial distribution within the rural community that could be explained by the different ecosystems and particularly the soil characteristics of this community. Finally, the presence of the S. dubia species appeared to be significantly associated with canine leishmaniasis seroprevalence in dogs. Conclusions/Significance Our data allow us to hypothesize that the species of the genus Sergentomyia and particularly the species S. dubia and S. schwetzi might be capable of transmitting canine leishmaniasis. These results challenge the dogma that leishmaniasis is exclusively transmitted by species of the genus Phlebotomus in the Old World. This hypothesis should be more thoroughly evaluated.

Life-history traits of Macrolophus pygmaeus with different prey foods

Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a generalist predatory mirid widely used in augmentative biological control of various insect pests in greenhouse tomato production in Europe, including the invasive tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera, Gelechiidae). However, its biocontrol efficacy often relies on the presence of alternative prey. The present study aimed at evaluating the effect of various prey foods (Ephestia kuehniella eggs, Bemisia tabaci nymphs, Tuta absoluta eggs and Macrosiphum euphorbiae nymphs) on some life history traits of M. pygmaeus. Both nymphal development and adult fertility of M. pygmaeus were significantly affected by prey food type, but not survival. Duration of nymphal stage was higher when M. pygmaeus fed on T. absoluta eggs compared to the other prey. Mean fertility of M. pygmaeus females was greatest when fed with B. tabaci nymphs, and was greater when offered M. euphorbiae aphids and E. kuehniella eggs than when offered T. absoluta eggs. Given the low quality of T. absoluta eggs, the efficacy of M. pygmaeus to control T. absoluta may be limited in the absence of other food sources. Experiments for assessing effectiveness of generalist predators should involve the possible impact of prey preference as well as a possible prey switching.

On the development cycle and ultrastructure of Vavraia culicis Weiser, 1947 (microsporida, pleistophoridae) with comments on the taxonomy of the genus Vavraia Weiser, 1977.

Vavraia culicis was studied using light and electron microscopy. The hosts were larvae of Anopheles gambiae collected in Senegal. Merogonial and sporogonial plasmodia had isolated nuclei. A thick amorphous coat was formed externally to the plasma membrane of the merogonial plasmodium, which developed into the envelope of the sporophorous vesicle. Division of merogonial and sporogonial plasmodia occurred by plasmotomy. Only one type of spores was produced. The polar filament was anisofilar. Meiosis was not observed.

Ultrastructure of Nosema stenocyprisDiarra & Toguebaye, 1994, a Microsporidian Parasite of Stenocypris major (Crustacea, Ostracoda, Cyprididae)

Summary Nosema stenocypris Diarra & Toguebaye , 1994 (Microsporida, Nosematidae) has been described from Stenocypris major (Crustacea, Ostracoda, Cyprididae). It develops in the muscles. Merogonial stages were not observed. The cellular envelope of young sporonts grows in thickness by addition of electron-dense material external to the plasma membrane. The sporoblasts are bounded by a thick electron-dense wall and transform directly into spores. Live mature spores are ovoid and measure 4.28 ± 0.19×2.61 ± 0.10 µm. Their wall can reach a thickness of 190 nm. The polar filament is isofilar with 14 coils and the polaroplast has an anterior lamellar part and a posterior vesicular part.

Life History Traits of Oomyzus sokolowskii Kurdjumov (Hymenoptera: Eulophidae), a Parasitoid of the Diamondback Moth

In this study the life-history of Oomyzus sokolowskii (Kurdjimov), a parasitoid of the diamondback moth (DBM) Plutella xylostella (L.) as characterized. The life cycle, adult size, fecundity, ovigeny, parthenogenesis, host age preference and host-searching behaviour by parasitoid females were studied under laboratory conditions. Oomyzus sokolowskiiapos;s life cycle lasted 15. 6 days. Sexual dimorphism was recorded, with females being bigger than males. The species is synovigenic. The parasitism rate was significantly different between mated and unmated females, which implied that mating stimulated the behaviour of parasitism. Thelythokous parthenogenesis was not recorded. Females could parasitize all larval stages and pre-pupae, but the parasitism rate was higher in the fourth larval stages of DBM. The host-seeking behaviour was influenced by host spatial patchiness; O. sokolowskii females performed better when they were placed in a 7 cm3 oviposition box. This study gives a better understanding of the life history traits of O. sokolowskii, which has been neglected in the biological control of DBM in tropical regions. The study suggests the use of O. sokolowski as a promising candidate for the management of DBM in cabbage in combination with other IPM strategies.

Performance of the parasitoid Oomyzus sokolowskii (Hymenoptera: Eulophidae) on its host Plutella xylostella (Lepidoptera: Plutellidae) under laboratory conditions

Oomyzus sokolowskii (Kurdjumov) is a gregarious larval-pupal parasitoid of the diamondback moth Plutella xylostella (L.). The objective of this study was to investigate the interactions between host and parasitoid by examining the effects of biotic factors such as gregariousness, host origin and stages, and female parasitoid age on the parasitism rate, developmental time, the number of offspring and the offspring sex ratio of O. sokolowskii under laboratory conditions. The percentage of parasitism and the number of parasitoids increased with the number of O. sokolowskii females. Oomyzus sokolowskii preferred fourth larval instars over other larval stages. The parasitism rate and the progeny production of O. sokolowskii decreased with parasitoid age; however, the developmental time and the sex ratio of the offspring were not significantly different. Our results confirm previous findings on larval preferences of O. sokolowskii. The study also confirmed the importance of geographical origin of the host on the performance of O. sokolowskii.

Pathogenicity of local Metarhizium anisopliae var. acridum strains on Locusta migratoria migratorioides Reiche and Farmaire and Zonocerus variegatus Linnaeus in Senegal

In order to reduce the cost and time of in vitro raised plants of Trichosanthes dioica Roxb., a minimal medium has been formulated by substituting costly growth regulators from the medium with a cost effective constituent, the coconut milk. A semisolid Murashige and Skoogs’s medium supplemented exclusively with 15% coconut milk showed the highest percentage of plantlet regeneration (99%) in the explants. When nodal, shoot-tip and immature leaf explants were cultured on this medium, rhizogenesis was observed in about 5 to 6 days of inoculation, followed by shoot formation in about 8 to 10 days. The fully developed plantlets, 10 to 12 cm in length with professed roots were obtained in about 20 days of inoculation in a single step without adding/changing growth regulators. After transplantation in the potted soil, these plantlets showed similar growth patterns as compared to the plants obtained from a conventional three-four step method of tissue culture experiments. Keywords: Coconut milk, tissue culture, Trichosanthes dioica Roxb

Influence of Oecophylla longinoda Latreille, 1802 (Hymenoptera: Formicidae) on Mango Infestation by Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) in Relation to Senegalese Orchard Design and Management Practices

Damage caused by the fruit fly Bactrocera dorsalis (Hendel) (syn. B. invadens Drew, Tsuruta & White) (Diptera: Tephritidae) on mangoes in Senegal leads to production losses. A potential biological control agent against this pest is the weaver ant Oecophylla longinoda Latreille (Hymenoptera: Formicidae). Senegalese mango-based orchards present a diversity in design and management practices that can influence the abundance of these two species in orchards. In this study we evaluated i) the ability of the O. longinoda ant to limit B. dorsalis damage in Senegalese orchards, and ii) variations in population abundance for these two species depending on orchard design and management practices. The study was conducted in Senegal in the Niayes area and the Thiès plateau. Fifteen orchards were sampled among three out of four kinds of orchards identified in this area: (1) ‘No-input mango diversified orchards’, (3) ‘Medium-input citrus-predominant orchards’ and (4) ‘Medium-input large mango- or citrus-predominant orchards’. In one of the orchards we measured infestation rates and numbers of fly pupae that developed from mangoes collected from trees (cv. Kent) ‘with’ and ‘without’ O. longinoda colonies over three harvesting periods (May, July and August) in 2013. The abundance of O. longinoda and B. dorsalis was measured for two months in the dry season and two others in the rainy season in the 15 orchards in 2012. The presence of O. longinoda on trees reduced the proportion of mangoes attacked by B. dorsalis as well as the number of pupae that developed from infested mangoes. The abundance of O. longinoda and B. dorsalis was negatively correlated. The abundance varied depending on the orchard design and management practices. O. longinoda abundance was greater in orchard types 1 and 3 than in type 4. Conversely, B. dorsalis abundance in the rainy season tended to be greater in orchard type 4 than in types 1 and 3. This study showed that O. longinoda is effective in limiting mango infestations by B. dorsalis. It also showed that the abundance of these two species was influenced by the orchard design and management practices. Therefore, using O. longinoda to control fruit flies is possible in Senegalese mango-based orchards by promoting weaver ant preservation.

The relationship between the diamondback moth, climatic factors, cabbage crops and natural enemies in a tropical area

ABSTRACT The impact of abiotic and biotic factors (rainfall, temperature, host plant and natural enemies) on population dynamics of the Plutella xylostella L. diamondback moth was investigated. The experiments were conducted during the rainy and dry seasons for two years (June 2009-April 2011) on unsprayed cabbage plots in Malika (Senegal). Every 10 days, 10 cabbages were randomly selected. Plutella xylostella larvae, pupae and parasitoid cocoons were recorded on each plant. Before each sampling, the diameters and ages of plants were recorded. Temperature and rainfall were also recorded during this study. Larvae and pupae of P. xylstella were higher for the dry season than the rainy season. There was a negative correlation between temperature and P. xylostella populations, and a strong relationship between P. xylostella populations and the age of cabbages. Females oviposited on young cabbages where the presence of young larvae was important, whereas older immature stages were mainly found in older cabbage plants. Parasitoid populations were higher for the dry season than the rainy season. High temperatures did not increase the pest populations and parasitism rate. There was no effect found on pest, plants and natural enemies due to rainfall. There was a positive correlation between pest populations and parasitism. Four Hymenoptera species were found: Oomyzus sokolowskii, Apanteles litae, Cotesia plutellae and Brachymeria citrae, but they were not efficient to control the P. xylostella populations. These results are important for understanding the factors that promote or inhibit pest populations and their natural enemies, and therefore essential for effective crop protection.