The feeding behaviour of cassava mealybug (Phenacoccus manihoti) was analysed by the electrical penetration graph technique (EPG, DC‐system) and by light microscopy. This study confirmed a typical phloem‐feeding behaviour with an aphid‐like predominance of extracellular pathways of stylets. Similarities of EPGs from mealybugs with those of aphids and whiteflies allowed adoption of standard pattern labelling. The main differences with aphid EPGs consisted of fewer but longer intracellular punctures (pd duration of 20 s vs 5–7 s for aphids), longer times to the first phloem‐ingestion period and a lower motility of stylets within the phloem searching process. Comparison of the feeding behaviour on 6 plant types, including two occasional hosts (Talinum and poinsettia), one cassava hybrid and three common cassava cultivars (Manihot esculenta), allowed differentiation of penetration profiles. Intracellular punctures were shorter on occasional hosts, on which phloem finding and subsequent ingestion were markedly delayed although a great variability within plants persisted. Chemical analysis of some secondary plant substances revealed that none of the plants tested contained detectable amounts of alkaloids, and that cyanides were restricted to true hosts (cassavas and Manihot hybrid). Levels of total flavonoids did not differ between hosts and non‐hosts, in contrast to those of phenolic acids. Preliminary correlations with EPG patterns are discussed. Résumé Le comportement alimentaire de la cochenille du manioc (Phenacoccus manihoti) a été étudié par électrographie de pénétration (EPG, analyse en courant continu) et par microscopie optique. Cette étude a permis de confirmer le caractère typiquement phloémophage de l'alimentation de cet Homoptère, présentant une large prédominance du trajet extracellulaire des stylets, comme cela est également observé chez les pucerons. Les similitudes des tracés EPG effectués sur cochenille et sur pucerons ou aleurodes ont permis d'adopter la même typologie du signal. Les principales différences avec les pucerons concernent le nombre moins important et la durée plus longue des ponctions intracellulaires (20 s en moyenne contre 5 à 7 s chez les pucerons), l'allongement du temps d'accès au phloème et une moins grande mobilité des stylets lors de la phase de recherche du phloème. La comparaison du comportement alimentaire sur 6 plantes, parmi lesquelles deux hôtes occasionnels (Talinum et poinsettia), un hybride et trois variétés courantes de manioc (Manihot esculenta), a permis de différencier plusieurs profils de pénétration. Les ponctions intracellulaires se sont révélées plus courtes sur hôtes occasionnels, qui induisent également, malgré la variabilité observée, un allongement net de la période de localisation du phloème et donc un retard à l'ingestion. Aucune des plantes testées ne contient d'alcaloîdes, et les composés cyanés se restreignent au genre Manihot, hôte naturel de la cochenille. Les flavonoîdes totaux ne permettent pas de distinguer plantes hôtes et non‐hôtes, à l...

Bracoviruses are domesticated viruses found in parasitic wasp genomes. They are composed of genes of nudiviral origin involved in particle production and proviral segments encoding virulence genes necessary for parasitism success. During particle production, proviral segments are amplified and individually packaged as DNA circles in nucleocapsids. These particles are injected by parasitic waspstogether with their eggs into host larvae. Bracovirus circles of two wasp species were reported toundergo chromosomal integration in parasitized host hemocytes, through a conserved sequence named Host Integration Motif (HIM). Here, we used bulk Illumina sequencing to survey integrations of Cotesia typhae bracovirus circles in the DNA of its host, the maize corn borer ( Sesamia nonagrioides ) seven days after parasitism. First, assembly and annotation of a high-quality genome for C. typhae enabled us to characterize 27 proviral segments clustered in proviral loci. Using these data, we characterized large numbers of chromosomal integrations (from 12 to 85 events per host haploid genome) for all 16 bracovirus circles containing a HIM. Integrations were found in four S. nonagrioides tissues and in the body of a caterpillar in which parasitism had failed. The 12 remaining circles do not integrate but are maintained at high levels in host tissues. Surprisingly, we found that HIM-mediated chromosomal integration has occurred at least six times accidentally in thewasp germline during evolution. Overall, our study furthers our understanding of wasp-host genome interactions and supports HIM-mediated chromosomal integration as a possible mechanism ofhorizontal transfer from wasps to their hosts. Importance Bracoviruses are endogenous domesticated viruses of parasitoid wasps that are injected together with wasp eggs into wasp host larvae during parasitism. Several studies have shown that some DNA circles packaged into bracovirus particles become integrated into host somatic genomes during parasitism, but the phenomenon has never been studied using non-targeted approaches. Here we use bulk Illumina sequencing to systematically characterize and quantify bracovirus circle integrations that occur in four tissues of the Mediterranean corn borer ( Sesamia nonagrioides ) during parasitism by the Cotesia typhae wasp. Our analysis reveals that all circles containing a host integration motif (HIM) integrate at substantial levels (from 12 to 85 integrations per host cell in total) in all tissues while other circles do not integrate. In addition to shedding new light on wasp-bracovirus-host interaction, our study supports HIM-mediated chromosomal integration of bracovirus as a possible source of wasp-to-host horizontal transfer with long term evolutionary consequences.

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Abstract. Lepidopterous stem borers are the main field insect pests that attack maize, Zea mays L. in tropical Africa. A survey was carried during the long and short rain cropping seasons of 2002 / 2003 across six main agro-climatic zones (ACZs) to determine the spatial distribution of important stem borer species in Kenya. A total of 474 visits were made in the seventy-eight localities conveniently chosen to represent each of the six ACZs. 189,600 stems were checked for infestation, of which 27,799 infested stems were destructively cut and dissected for stem borer larvae identification. An average of 1.4 stem borer larvae were recovered per infested plant. 54.5% of the recovered larvae were identified as Chilo partellus (Swinhoe) (Crambidae), 39.7% as Busseola fusca (Fuller) (Noctuidae), 4.5% as Sesamia calamistis Hampson (Noctuidae) and 0.8% as Chilo orichalcociliellus (Strand) (Crambidae). Minor species present included Eldana saccharina Walker (Pyralidae), Sesamia nonagrioides (Lefebvre) (Noctuidae), Sesamia cretica Lederer (Noctuidae), Sesamia sp. (Noctuidae), Sciomesa piscator Fletcher (Noctuidae), Busseola sp near phaia (Noctuidae), Chilo sp, Ematheudes sp 1 (Pyralidae) and Ematheudes sp 2 (Pyralidae). Farms were grouped into respective ACZs for statistical analysis and subsequent comparison of dominant species. Results indicated that B. fusca was the dominant stem borer species in high potential zones (highland tropics, moist transitional zone and moist midaltitude) while the exotic C. partellus dominated smallholder farms in low potential zones (dry midaltitude, dry transional and lowland tropical zone). Within each ACZs, there was evidence of variation in species proportions between seasons. These spatio-temporal differences in community structure are discussed in terms of agro-climatic biological adaptations.Résumé. Distribution, ravages et préférences agro-climatiques des lépidoptères foreurs de tige du maïs au Kenya. Une enquête a été menée dans les 6 principales régions agro-écologiques du Kenya, pendant les longues et courtes saisons des pluies de 2002/2003, afin de déterminer la distribution spatiale des lépidoptères foreurs de graminées attaquant le maïs Zea mays L. Un total de 474 échantillonnages a été réalisé dans les 78 localités représentatives des six régions agroécologiques. On a vérifié l'infestation de 189,600 tiges et les 27799 tiges infestées ont été récoltées et disséquées afin d'identifier les foreurs. En moyenne, 1,4 larves de foreur ont été trouvées par plante infestée; 54,5% des larves récoltées étaient des Chilo partellus Swinhoe (Crambidae), 39,7% des Busseola fusca (Fuller) (Noctuidae), 4,5% des Sesamia calamistis Hampson (Noctuidae) et 0,8% des Chilo orichalcociliellus Strand (Crambidae). Des espèces peu importantes ont également été trouvées telles que Eldana saccharina Walker (Pyralidae), Sesamia nonagrioides Lefebvre (Noctuidae), Sesamia cretica Lederer (Noctuidae), Sesamia sp. (Noctuidae), Sciomesa piscator Fletcher (Noctuidae), Busseola sp near phaia (Noctuidae), Chilo s...

Stems of susceptible and resistant cassava plants have been cytologically investigated for their defense reactions to an aggressive strain of Xanthomonas campestris pv. manihotis. Histochemistry, in conjunction with gold cytochemistry, revealed that in susceptible and resistant plants, phloem and xylem parenchyma cells displayed a wide range of responses that limited the bacterial growth within the infected plants. Lignification and suberization associated with callose deposition were effective mechanisms that reinforced host barriers in the phloem. In the infected xylem, vessels were plugged by a material of pectic and (or) lignin-like origin. Flavonoids have been seen to be incorporated in secondary cell wall coatings. These reactions occurred at a higher intensity in the resistant plants. The number of phoem and xylem cells producing autofluorescent compounds was higher in infected resistant plants than in susceptible plants. Reactions have been observed in the resistant variety only, such as secretion of phenol-like molecules by tyloses and hyperplasic activity of phloem cells that compartmentalized bacterial lysis pockets, which are potent secondary inoculum sources.Key words: lignin, suberin, callose, phenol, tylose, flavonoid, pectin.

The fall armyworm (FAW), Spodoptera frugiperda (JE Smith, 1797), is a serious pest of several crops, particularly maize and other cereals. It has long been known as a pest in the Americas and has invaded most of Africa and parts of the Middle East, Asia, and Australia in the last six years. Its new status as an invasive species causing serious damage in many regions worldwide has highlighted the need for better understanding and has generated much research. In this article, we provide a comprehensive review of FAW covering its (i) taxonomy, biology, ecology, genomics, and microbiome, (ii) worldwide status and geographic spread, (iii) potential for geographic expansion and quarantine measures in place, and (iv) management including monitoring, sampling, forecasting, biological control, biopesticides, agroecological strategies, chemical control, insecticide resistance, effects of insecticides on natural enemies, as well as conventional and transgenic resistant cultivars. We conclude with recommendations for research to enhance the sustainable management of FAW in invaded regions.

Abstract. Presence of wild host plants of stem borers in cereal-growing areas has been considered as reservoirs of lepidopteran stem borers, responsible for attack of crops during the growing season. Surveys to catalogue hosts and borers as well as to assess the abundance of the hosts were carried out during the cropping and non-cropping seasons in different agro-ecological zones along varying altitude gradient in Kenya. A total of 61 stem borer species belonging to families Noctuidae (25), Crambidae (14), Pyralidae (9), Tortricidae (11) and Cossidae (2) were recovered from 42 wild plant species. Two noctuids, Busseola fusca (Fuller), Sesamia calamistis Hampson, and two crambids, Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) were the four main borer species found associated with maize plants. In the wild, B. fusca was recovered from a limited number of host plant species and among them were Sorghum arundinaceum (Desvaux) Stapf, Setaria megaphylla (Steudel) T. Durand & Schinz, Arundo donax L. and Pennisetum purpureum Schumacher. In contrast, the host range of C. partellus was considerably wider [13 for S. calamistis]. However, the number of larvae of these species was lower in the wild compared to cultivated fi elds, thus the role of natural habitat as a reservoir for cereal stem borers requires further studies. Importance of the wild host plants as well as borer diversity along the altitudinal gradient is discussed.Résumé. Le rôle des plantes hôtes sauvages dans l'abondance des lépidoptères foreurs de graminées selon un gradient altitudinal au Kenya. La présence de plantes hôtes sauvages de foreurs autour des parcelles cultivées a toujours été considérée comme préjudiciable à la production des céréales dans la mesure où elles constituent des réservoirs pour les foreurs. Des enquêtes ont été menées au Kenya, pendant et en dehors des périodes culturales, selon un gradient altitudinal, afi n de déterminer le rôle de ces plantes hôtes sur les populations de ravageurs. Soixante et une espèces de lépidoptères foreurs appartenant aux familles des Noctuidae (25), Crambidae (14), Pyralidae (9), Tortricidae (11) et Cossidae (2) ont été récoltées sur 42 plantes hôtes sauvages. Les principales espèces de foreurs associées au maïs sont Busseola fusca (Fuller) et Sesamia calamistis Hampson (Noctuidae) et Chilo partellus (Swinhoe) et Chilo orichalcociliellus (Strand) (Crambidae). Dans les habitats sauvages, B. fusca a été trouvé sur un nombre restreint de plantes hôtes sauvages telles que Sorghum arundinaceum (Desvaux) Stapf, Setaria megaphylla (Steudel) T. Durand & Schinz, Arundo donax L. and Pennisetum purpureum Schumacher. A l`inverse, S. calamistis et C. partellus ont été trouvées associées à plus de plantes hôtes sauvages [S. calamistis (13), C. partellus (5)]. Toutefois, le nombre total de chenilles de ces quatre espèces de ravageur trouvé dans les habitats sauvages est très inférieur à celui trouvé dans les parcelles cultivées, aussi le rôle des habitats sauvages en tant que réservoir pour les lépidopt...

Identification and assay of cyanogenic and phenolic compounds in phloem sap of cassava (Manihot esculenta Crantz, Euphorbiaceae) and in honeydew of the cassava mealybug Phenacoccus manihoti Matt. Ferr. (Homoptera, Pseudococcidae) were realised.Cyanogenic glucosides and three flavonoid glycosides (rutin, kaempferol glycoside-1 and kaempferol glycoside-2) were found to be translocated in cassava phloem sap and consumed by the mealybug. Differences in profiles of secondary compounds of phloem sap and honeydew samples, characterised mainly by the appearance of free cyanide and of a free flavonoid, suggest the metabolic processing of at least some of the ingested compounds.The relationship between foliar concentrations of these different compounds and expression of the antibiotic resistance of cassava towards P. manihoti was also investigated in 7 varieties of cassava and in the 'faux-caoutchouc' hybrid. Infestation by mealybug was followed by a clear increase in levels of both rutin and kaempferol glycoside-2, while no modification in cyanide contents was noted. The best rank correlation between antibiotic resistance (measured by the intrinsic rate of increase re) and secondary compounds analyzed is observed with rutin contents of infested plants (p=-0.73; p=0.05). The possible implication of this compound in the biochemical mechanisms accompanying cassava defence reaction to mealybug attack is discussed.