First report of Spodoptera frugiperda (Lepidoptera: Noctuidae) on Onion (Allium cepa L.) in South Kivu, Eastern DR Congo

The fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797), has become one of the most devastating pests in the world with diverse host range. To develop effective integrated management strategies against S. frugiperda, it is crucial to know its alternative host plants. In this study, we provide the first information on the occurrence of S. frugiperda in onion crops in Africa. Monitoring was carried out during the 2019 and 2020 growing seasons in onion monoculture and in intercropping with groundnut to detect the presence and assess the incidence of S. frugiperda. The highest average incidence (2.88%) and larval density (0.79 per 9 m2) were observed in onion monoculture. The classification of the onion leaf damage rating scale indicated low S. frugiperda infestation. This suggests that future studies will need to assess this aspect which we consider to be a survival strategy to maintain its population throughout the year, which contributes to sustain the insect in the study area during times when its preferred hosts are not present. Furthermore, genetic studies are needed to provide a better explanation of the ecology of this pest and to find out which of the two existing strain infests onions or whether it is an unknown hybrid population of S. frugiperda

Evaluation of the productivity of seven varieties of wheat (Triticum aestivum) through integrated soil fertility management in Kaziba, South Kivu, DR Congo

Due to high demand for food resources as a result of increasing population, the promotion of large-scale crops such as wheat has become essential. Unfortunately, soil infertility and a lack of improved seed are major constraints on the expansion of this crop in Kaziba, a mountainous rural area in South Kivu. The productivity of seven wheat varieties (Farari, Kayira, Kima, Lokale, Mbega, Nyumbu and Popo) was evaluated under organic and mineral fertilizer during the 2013-2014 crop season on poor soil in South Kivu (DR Congo). NPK 17-17-17, farmyard manure and their combination were applied as fertilizers in a split-plot trial design with three replications. The observations focused on the growth and yield parameters, and the results revealed differences between varieties, treatments and interactions. The NPK + farmyard manure treatment gave the highest mean yield (1317.2 kg), Kayira was the most productive variety (1584.2 kg), and the interaction Kayira X farmyard manure was the most effective (2874.9 kg). The variety Kayira would seem to be indicated, with farmyard manure as the recommended fertilizer, being locally accessible and easily usable for promoting wheat in the region

Epidémiologie, diversité génétique, distribution et contrôle des virus de la mosaïque africaine du manioc et de son vecteur (Bemisia tabaci) dans la région du Sud-Kivu en République Démocratique du Congo

An assessment of the epidemiology of cassava pests and diseases in the South Kivu region of the D.R. Congo, and of the molecular diagnosis of cassava mosaic viruses based on their AC2 and AC4 genes, showed that there is a high disease prevalence in the low-altitude areas where cassava is grown intensively. Two virus species (African cassava mosaic virus, ACMV, and East African cassava mosaic virus, EACMV) occur in this region both in cassava plants and in their whitefly vectors (Bemisia tabaci), resulting in severe symptoms and major yield losses. These losses were higher in low-altitude areas where EACMV-UG alone, or in a dual infection with ACMV, was frequent. The incidence of cassava mosaic disease (CMD) ranged from 65 to 100% in low-altitude areas and from 9.5 to 77.7% in high altitude ones. The number of whiteflies per leaf was 8-17.9 and 1-11.3, respectively. The disease severity scores reflected these differences. Based on a phylogenetic study of the partial sequences of their DNA A genome, the ACMV isolates clustered into five distinct groups, whereas the EACMV-UG isolates fell into only two groups, probably due to their more recent history in the region. The whitefly population, which was studied using the sequences of Cytochrome oxydase I of the mitochondrial gene (mtCOI), was homogenous independently of its host plants. Among the 10 major local cassava varieties and five improved genotypes studied, two local varieties (Pharmakina and Cizinduka) and three improved genotypes (MM96/002, MM96/157, MM96/6967) were the most productive and the most tolerant of the disease. The cultivation of cassava in an intercropping system resulted in a reduction of 19% and 33.3% in disease incidence and its vector population, respectively. The study highlighted the differential distribution and impact of cassava mosaic disease depending upon agro-ecosystem characteristics, with factors such as altitude, genotype, virus species and infection period playing a role in the disease epidemic. Under conducive conditions, yield losses ranging from 77.5 to 97.3% have been recorded. Our results indicate that CMD management needs to be considered as more complex than simply managing a viral disease. We propose that an integrative approach should be adopted, taking into account the agro-ecosystem in which cassava is grown, the type of cropping system, varietal adaptation and vector presence and distribution, as well as the incidence of other endemic cassava pests and diseases. It is also very important to ensure the availability of disease-free cassava cuttings and well-adapted cassava varieties.L’épidémiologie et la caractérisation moléculaire des virus de la mosaïque du manioc ont montré une distribution selon les agro-écosystèmes. En basse altitude l’incidence, la sévérité ainsi que la population du vecteur sont plus élevées qu’en moyenne et haute altitude. Des incidences allant de 65-100% et de 9,5 à 77,7% et un nombre de mouches blanches par feuille de 8-17,9 et 1-11,3 sont rapportées dans les zones respectives. La même tendance est observée pour les autres maladies et ravageurs. Les analyses moléculaires révèlent une population du vecteur homogène et seules deux espèces des begomovirus du manioc (ACMV et EACMV). La sévérité est liée à la prédominance des souches EACMV-UG plus virulentes et plus d’infections mixtes en basse altitude qu’en moyenne et haute altitude où prédominent des souches ACMV moins virulentes. Les souches ACMV forment cinq groupes distincts alors que les souches EACMV-UG n’en forment que deux, probablement au vu de leur histoire récente dans la région. Parmi dix variétés locales comparées à cinq variétés améliorées, deux locales (Pharmakina et Cizinduka) et trois améliorées (MM96/002, MM96/157 et MM96/6967) sont plus productives et tolérantes. La culture en association permet de réduire respectivement de 19% et 33,3% les valeurs de l’incidence et de la population du vecteur. Cette étude montre que l’épidémiologie et l’impact de la maladie sont liés à l’adaptation des génotypes dans l’agro-écosystème où ils sont cultivés en interaction avec d’autres facteurs tels que les souches des virus, la période d’infection ainsi que le système de culture. Elle souligne la nécessité d’une approche intégrée qui tienne compte à la fois de tous ces facteurs, du vecteur et de sa distribution, sans oublier les autres maladies et ravageurs.(AGRO 3) -- UCL, 201

Cassava mosaic disease yield loss assessment under various altitude agroecosystems in the sudKivu region, Democratic Republic of Congo

Cassava mosaic disease (CMD) is reported as the most important constraint on cassava production in SubSaharan Africa. Yield losses of 2595% are reported. The use of resistant genotypes is one of the components for its integrated management. However its impact on genotypes behavior depends on infection period, age of the infected plants, environment and virus species or strain in cause. This study was carried out to assess its impact in farmers’ fields and the behavior of 14 genotypes under high epidemic pressure in the SudKivu province, at the East of Democratic Republic of Congo (DRC). Early infections have induced 77,5% to 97,3% of yield losses whereas 44,9 to 80% were recorded for cassava plants infected during thirteenth to twentyfourth weeks after planting. The highest yield losses were recorded in low altitude where more EACMVUG and dual infections were reported. Improved resistant genotypes MM96/002, MM96/0157 and MM96/1920 allowed harvesting more than 30 T/ha and didn’t show any symptoms whereas MM96/6967 and Mvuama have developed symptoms at harvest. Local landraces were susceptible to CMD and developed symptoms during the whole season until harvest. However two of them, Pharmakina and Cizinduka yielded more than 50 T/ha of tubers and associated symptoms were moderate. Two improved and two local cassava genotypes are recommended in this area always making sure to use healthy cuttings

Dynamics of customary land rights and its impact on the agronomic choices for small farmers in the South Kivu province, Eastern DR Congo

In Africa, there is still observed a land related legal plurality despite innovations undertaken since colonial times. In DR Congo, while by law land remains the property of the State, it remains difficult to manage rural lands, ignoring customary practices. In fact, alongside the “modern” land administration, the majority of rural lands are covered by customary contracts. Meanwhile, these contracts have evolved due to different socio-political issues in the DRC and particularly in its eastern part. This study aimed at understanding these changes and thus the impact resulted in agricultural activities, especially the small farmers’ technology choice. The study is based on households’ surveys in the Mbinga Sud zone as well as from other stakeholders on land in the Kalehe territory, South Kivu province, eastern DRC. Through this study, it is noted that customary land contracts have sufficiently evolved due to the population growth, innovations taken in land administration in the country, the wars that occurred in the eastern DR Congo, the attractiveness of rural land by elites and rich businessmen leading to land concentration etc. Given this situation, some practices such as purchase and lease of land were thus developed to cope with weak customary land acquisition mechanisms, the land scarcity and / or land depletion and the fear of land grabbing by the strongest. These changes also have an impact on some agricultural practices, including the fertilization of farms, the choice of crops and varieties to grow as well as many other cultivation techniques

L’agriculture familiale à l’épreuve de la concurrence foncière au Sud-Kivu

peer reviewedEn RDC, malgré le grand potentiel foncier, on observe de fortes inégalités dans l’accès à la terre, entretenues entre autres par la gestion foncière telle qu’organisée actuellement dans le pays. Ce problème se présente avec une plus grande ampleur à l’est de la RD Congo et au Sud Kivu en particulier du fait de très fortes densités de population et de la ruée sur les terres qui s’y observent. Cet article présente les résultats d’une étude qui avait comme objectif de déterminer la manière dont les ménages font face à cette situation et la façon dont leurs activités agricoles en sont affectées. Il repose sur une enquête conduite en territoire de Kalehe, en province du Sud-Kivu auprès d’un échantillon de 120 ménages paysans tirés aléatoirement dans quatre localités du groupement Mbinga Sud à savoir Bushushu, Munanira, Cibanda et Tshibanja. Les informations collectées auprès de ménages ont été complétées par celles obtenues auprès d’autres parties prenantes autour du foncier dans le milieu dont les organisations locales et le pouvoir public incluant l’autorité coutumière. Il ressort des résultats obtenus, des difficultés réelles dans l’accès à la terre qui se traduisent par des faibles étendues cultivées et une sérieuse difficulté à acquérir de nouveaux champs, les anciennes procédures basées sur la coutume, n’étant plus applicables. Dans ces conditions, la location de terres se développe comme alternative. Celle-ci s’accompagne d’un grand nombre de contraintes à savoir le prix élevé, une courte durée, la proscription de certaines cultures parfois rentables, et des contrats précaires qui découragent certaines pratiques culturales. Ces problèmes, associés à d’autres contraintes auxquelles les paysans font face dans le milieu (faible utilisation des semences sélectionnées, maladies et ravageurs des cultures, faible fertilité des champs etc.), se traduisent par des rendements très faibles, mettant en danger la sécurité alimentaire (à travers notamment la diminution du nombre et de la qualité des repas pour les ménages) et les conditions de subsistance déjà précaires à l’est de la RDC

Contribution of cassava-maize-common beans inter-cropping system to the management of cassava mosaic disease and its vector

Cassava mosaic disease (CMD) is reported as the most important constraint on cassava in Sub-Saharan Africa. The understanding of the disease epidemiology, the genetic diversity of the virus and its vector is a key factor for the disease management. In this study, cropping system associating cassava, common beans (Phaseolus vulgaris) and maize, the most frequent cassava cropping system in Eastern DR Congo, was investigated to understand the disease characteristics and existing interactions within this pathosystem: cassava mosaic begomoviruses (CMBs), cassava and non-cassava plants, Bemisia tabaci population and agro-ecosystems in which they are found. Different geographic locations mainly depending on the altitude levels showed a significant influence on CMD incidence and severity, and whitefly population. CMD and its vector pressure were high in low altitude, but significant decrease was observed in intercropped fields. Under high epidemic pressure, respective decreases of 19% and of 33.3% were recorded on disease incidence and whitefly population. Only two CMBs (ACMV and EACMV-UG) were detected both in cassava plants and in whiteflies collected on cassava and other plant species. In contrast, no CMBs were detected in non-cassava associated plants. Bemisia tabaci characterization based on MtCOI sequences analysis revealed the presence of a single haplotype close to Ug1, irrespective of the plant species on which the insects were collected. The low diversity of the CMBs and whitefly population combined with the impact of local intercropping system cassava, common beans and maize are discussed, underlining the interest of the other ways of CMD management besides crop resistance strategies

Banana Tree Infected with Banana Bunchy Top Virus Attracts Pentalonia nigronervosa Aphids Through Increased Volatile Organic Compounds Emission

Banana plants are affected by various viral diseases, among which the most devastating is the "bunchy top", caused by the Banana bunchy top virus (BBTV) and transmitted by the aphid Pentalonia nigronervosa Coquerel. The effect of BBTV on attraction mechanisms of dessert and plantain banana plants on the vector remains far from elucidated. For that, attractiveness tests were carried out using a two columns olfactometer for apterous aphids, and a flight cage experiment for alate aphids. Volatile Organic Compounds (VOCs) emitted by either healthy or BBTV-infected banana plants were identified using a dynamic extraction system and gas-chromatography mass-spectrometry (GC–MS) analysis. Behavioral results revealed a stronger attraction of aphids towards infected banana plants (independently from the variety), and towards the plantain variety (independently from the infection status). GC–MS results revealed that infected banana plants produced VOCs of the same mixture as healthy banana plants but in much higher quantities. In addition, VOCs produced by dessert and plantain banana plants were different in nature, and plantains produced higher quantities than dessert banana trees. This work opens interesting opportunities for biological control of P. nigronervosa, for example by luring away the aphid from banana plants through manipulation of olfactory cues

The aphid Pentalonia nigronervosa (Hemiptera: Aphididae) takes advantage from the quality change in banana plant associated with Banana bunchy top virus infection.

peer reviewedViral diseases can change plant metabolism, with potential impacts on the quality of the plant's food supply for insect pests, including virus vectors. The banana aphid, Pentalonia nigronervosa Coquerel, is the vector of the Banana bunchy top virus (BBTV), the causal agent of Banana bunchy top disease (BBTD), the most devastating viral disease of bananas in the world. The effect of BBTV on the life-history traits and population dynamics of P. nigronervosa remains poorly understood. We therefore studied the survival rate, longevity, daily fecundity per aphid, tibia length, population growth, and winged morph production of a P. nigronervosa clone grown on healthy or infected, dessert, or plantain banana plants. We found that daily fecundity was higher on infected banana than on healthy banana plants (plantain and dessert), and on plantain than on dessert banana plants (healthy and infected). Survival and longevity were lower on infected dessert bananas than on other types of bananas. In addition, virus infection resulted in a decrease in aphid hind tibia length on both plant genotypes. The survival and fecundity table revealed that the aphid net reproduction rate (Ro) was highest on plantains (especially infected plantain), and the intrinsic growth rate (r) was highest on infected plants. Finally, the increase of aphids and alate production was faster first on infected plantain, then on healthy plantain, and lower on dessert banana (infected and uninfected). Our results reinforce the idea of indirect and plant genotype-dependent manipulation of P. nigronervosa by the BBTV