Parasitism of Lepidopterous Stem Borers in Cultivated and Natural Habitats

Plant infestation, stem borer density, parasitism, and parasitoid abundance were assessed during two years in two host plants, Zea mays (L.) (Cyperales: Poaceae) and Sorghum bicolor (L.) (Cyperales: Poaceae), in cultivated habitats. The four major host plants (Cyperus spp., Panicum spp., Pennisetum spp., and Sorghum spp.) found in natural habitats were also assessed, and both the cultivated and natural habitat species occurred in four agroecological zones in Kenya. Across habitats, plant infestation (23.2%), stem borer density (2.2 per plant), and larval parasitism (15.0%) were highest in maize in cultivated habitats. Pupal parasitism was not higher than 4.7% in both habitats, and did not vary with locality during each season or with host plant between each season. Cotesia sesamiae (Cameron) and C. flavipes Cameron (Hymenoptera: Braconidae) were the key parasitoids in cultivated habitats (both species accounted for 76.4% of parasitized stem borers in cereal crops), but not in natural habitats (the two Cotesia species accounted for 14.5% of parasitized stem borers in wild host plants). No single parasitoid species exerted high parasitism rates on stem borer populations in wild host plants. Low stem borer densities across seasons in natural habitats indicate that cereal stem borer pests do not necessarily survive the non-cropping season feeding actively in wild host plants. Although natural habitats provided refuges for some parasitoid species, stem borer parasitism was generally low in wild host plants. Overall, because parasitoids contribute little in reducing cereal stem borer pest populations in cultivated habitats, there is need to further enhance their effectiveness in the field to regulate these pests

Cereal stemborder species complex and establishment of Cotesia flavpipes Cameron in eastern Uganda

Studies were conducted in two districts of eastern Uganda from 1997 to 1999 to introduce and monitor the establishment of an exotic parasitoid, Cotesia flavipes Cameron (Hymenoptera: Braconidae), for the control of the stemborer Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), and also to determine the stemborer species complex in maize and sorghum. The study confirmed the presence of four important stemborers, two pyralids Ch. partellus and Eldana saccharina Walker and two noctuids, Busseola fusca Fuller and Sesamia calamistis Hampson. Chilo partellus was dominant, constituting 53-88% of stemborers found followed by B. fusca at 8-37 %. The most abundant local parasitoid was the larval parasitoid Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae). The pupal parasitoids Pediobius furvus Gahan (Hymenoptera: Eulophidae) and Dentichasmias busseolae Heinrich (Hymenoptera: Ichneumonidae) were also recorded. Parasitism of Co. sesamiae on Ch. partellus ranged between 0 and 13.1 %. The introduced Co. flavipes was recovered from all sites in four consecutive seasons (between 1998 and 1999) causing parasitism of between 4 and 32.9 % on Ch. partellus. Cotesia flavipes was also recovered from the indigenous stemborers B. fusca and S. calamistis. This study indicates that Co. flavipes has established in eastern Uganda. RÉSUMÉ Des études ont été menées dans deux départements en Ouganda entre 1997 et 1999 infin d'introduire et de suivre l'aclimatation d'un parasitoïde exotique, Cotesia flavipes Cameron (Hymenoptera: Braconidae), dans le cadre de la lutte contre le foreur, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), et de determiner le complexe d'espèces de foreurs sur maïs et sorgho dans cette région. Cette étude a confirmé la présence de 4 espèces importantes de foreurs; deux pyrales, Ch. partellus et Eldana saccharina Walker et deux noctuidés Busseola fusca Fuller et Sesamia calamistis Hampson. Chilo partellus était l'espèce dominante formant près de 53-88% des borers collectés, suivit par B. fusca à 8-37 %. Le parasitoïde local le plus abundant a été le parasitoïde larvaire Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae). Les parasitoïdes des pupes Pediobius furvus Gahan (Hymenoptera: Eulophidae) et Dentichasmias busseolae Heinrich (Hymenoptera: Ichneumonidae) ont aussi été trouvés. Le parasitisme par Co. sesamiae sur Ch. partellus a varié entre 0 et 13.1%. Le parasitoïde introduit Co. flavipes a été collecté sur tous les sites pendant quatres saisons consecutives (entre 1998 et 1999) avec un taux de parasitisme entre 4 et 32.9 % sur Ch. partellus. Cotesia flavipes a aussi été collecté sur des foreurs locaux , B. fusca et S. calamistis. Cette étude a montré que Co. flavipes s'est acclimaté dans l'est de l'Ouganda

Abundance and diversity of lepidopteran stemborers and their parasitoids on selected wild grasses in Uganda

Surveys were conducted in four agroecological zones in Uganda to catalogue wild host plants of lepidopteran stemborers. Among those sampled, Panicum maximum, Pennisetum purpureum, Pennisetum polystachion and Sorghum arundinaceum were selected for further studies on stemborer diversity and density. Overall, stemborer incidence was low (< 10.8%) with the highest infestations on S. arundinaceum. Among the 11 borer species identified, there were seven noctuids, two crambids, one pyralid and one unidentified cossid. The economically important crambid Chilo partellus and the noctuid Busseola fusca were mostly found on S. arundinaceum and were rare on the other three grass species. Braconid larval parasitoids were commonly obtained from C partellus on S. arundinaceum and parasitoids of Sesamia spp. were most often found on P. purpureum. We concluded that in Uganda, with the exception of S. arundinaceum, wild grasses play a minor role in the seasonal persistence of C partellus and B. jusca

Buakea (Lepidoptera : Noctuidae), a new genus of African stem borers : morphological, ecological and molecular data

A new genus of African stem borers of the subtribe Sesamiina (Lepidoptera: Noctuidae), Buakea gen. n., is described as well as the three species it includes, two new, B. venusta sp. n. and B. kaeuae sp. n., and a species that until now was placed in the genus Busseola Thurau, B. obliquifascia (Hampson) comb. n. The three species are monophagous on different graminaceous host plants, and the two sister species B. kaeaue and B. obliquifascia were collected in different ecological zones and altitudes, which suggests an ecological mode of speciation. Bayesian and maximum likelihood phylogenies inferred from two mitochondrial genes showed that the genus is monophyletic and does not share a recent common ancestor with the genus Busseola. However no strongly supported phylogenetic relationship could be established with the other six genera of the subtribe included in the analysis

Systematics and molecular phylogeny of two African stem borer genera, Sciomesa Tams & Bowden and Carelis Bowden (Lepidoptera : Noctuidae)

Currently, the systematics of the African noctuid stem borers of the subtribe Sesamiina, which include major pests of cereals, is confused. In addition, their ecology is poorly known, as are the factors influencing their evolution. In this paper, we address these shortcomings for two genera of the Sesamiina, Sciomesa Tams & Bowden and Carelis Bowden. Mixed Bayesian phylogenetic analysis, which included their host plants and two mitochondrial genes, showed the genus Sciomesa to be polyphyletic. Two new genera were created, Pirateolea and Feraxinia. The genus Carelis proved to be paraphyletic and was subdivided into two sub-genera. The genera Sciomesa, Carelis and Pirateolea (named the 'Sciomesa genus group') share morphological traits, and the phylogenetic analysis showed that they had a common ancestor living on Cyperaceae and that they were distant from the genus Feraxinia belonging to another clade which had an ancestor living on Poaceae. Seven new species were described: Sciomesa gnosia sp. n., Sciomesia bua sp. n., Pirateolea nola gen. n, sp. n., Feraxinia serena gen. n., sp. n., Carelis australis sp. n., Carelis transversa sp. n. and Carelis agnae sp. n. Ten species were sunk as synonyms: Sciomesa mesoscia (Hampson) syn. n., Sciomesa mirifica Laporte syn. n., Sciomesa constantini Laporte syn. n. and Sciomesa etchecopari Laporte syn. n. are synonyms of Sciomesa mesophaea (Aurivillius); Acrapex sparsipucta Laporte syn. n. is a synonym of Sciomesa excelsa (Laporte) comb. n.; Acrapex congitae Laporte syn. n., Sesamia minuta Laporte syn. n. and Sesamia minuscula Laporte syn. n. are synonyms of Sciomesa boulardi (Laporte) comb. n.; Acrapex bryae Laporte syn. n. and Acrapex fayei Laporte syn. n. are synonyms of Feraxinia jemjemensis (Laporte) comb. n. Eleven new combinations were created: Sciomesa excelsa (Laporte) comb. n., Sciomesa boulardi (Laporte) comb. n., Sciomesa punctipennis (Kruger) comb. n., Pirateolea piscator (Fletcher) comb. n., Pirateolea argocyma (Fletcher) comb. n., Pirateolea cyclophora (Fletcher) comb. n., Pirateolea ochroneura (Fletcher) comb. n., Pirateolea funebris (Kruger) comb. n., Feraxinia nyei (Fletcher) comb. n., Feraxinia jemjemensis (Laporte) comb. n. and Carelis biluma (Nye) comb. n

Morphological reinforcement, ancient introgressive hybridization and species delimitation in African stem-borer species of the genus Sesamia Guenée (Lepidoptera : Noctuidae)

Species delimitation, an issue central to systematics and biodiversity studies, is addressed in the epunctifera group of the stem borer genus Sesamia Guenee (Lepidoptera: Noctuidae). This group is composed of four sub-Saharan species: Sesamia poephaga Tams & Bowden; Sesamia epunctifera Hampson; Sesamia penniseti Tams & Bowden; and Sesamia poebora Tams & Bowden, the taxonomic status of which was unclear. The first species was considered a possible synonym of the second, and the third species was considered a possible synonym of the fourth. An analysis combining morphological, ecological and molecular data enables us to conclude that S. epunctifera and S. poephaga are different species, and that S. poebora is a synonym of S. penniseti. Two new species were discovered: Sesamia firmata sp.n. and Sesamia veronica sp.n. Sesamia firmata sp.n. has atypical genitalic morphology, suggesting a strong selection resulting in a reinforcement of pre-zygotic isolation. Some specimens previously identified as S. penniseti on the basis of morphology are sisters to S. epunctifera on the mitochondrial tree, and are connected to S. penniseti on the nuclear tree. The mitochondrial distance from S. penniseti and S. epunctifera is 7.6% and 3.9%, respectively, suggesting an ancient mitochondrial introgression from S. epunctifera into S. penniseti. The possible causes of the reinforcement and introgressive hybridization are discussed. This case of mitochondrial introgression, uncommon in Lepidoptera, in which females are the heterogametic sex, may be an exception to Haldane's rule. The hybrid is assigned the rank of species and named Sesamia pennipuncta sp.n

Systematics and molecular phylogeny of two African stem borer genera, Sciomesa...

http://dx.doi.org/10.1017/S000748530999072