Richard T. Ghogomu

Musa Germplasm A and B Genomic Composition Differentially Affects Their Susceptibility to Banana Bunchy Top Virus and Its Aphid Vector, Pentalonia nigronervosa

Sergine Ngatat, Rachid Hanna, Jules Lienou, Richard Ghogomu, Sidonie Prisca K. Nguidang, Aime Cheoh Enoh and 6 more

Plants

Banana bunchy top disease (BBTD), caused by the banana bunchy top virus (BBTV, genus Babuvirus), is the most destructive viral disease of banana and plantain (Musa spp.). The virus is transmitted persistently by the banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae). While research efforts have focused on screening Musa genotypes for BBTD resistance, comparatively little work has been carried out to identify resistance to banana aphids. This study assessed 44 Musa germplasm of different A and B genome composition for the performance of banana aphids under semicontrolled environmental screenhouse conditions and in a field trial established in a BBTD endemic location. In the screenhouse, the AA diploid Calcutta 4 had the lowest apterous aphid density per plant (9.7 ± 4.6) compared with AAB triploid Waema, which had the highest aphid densities (395.6 ± 20.8). In the field, the highest apterous aphid density per plant (29.2 ± 6.7) occurred on the AAB triploid Batard and the lowest (0.4 ± 0.2) on the AA diploid Pisang Tongat. The AA diploid Tapo was highly susceptible to BBTD (100% infection) compared with the genotypes Balonkawe (ABB), PITA 21 (AAB), Calcutta 4 (AA), and Balbisiana Los Banos (BB), which remained uninfected. The Musa genotypes with apparent resistance to BBTD and least susceptibility to aphid population growth provide options for considering aphid and BBTD resistance in banana and plantain breeding programs.

• #plant virus research studies
• #cocoa and sweet potato agronomy
• #banana cultivation and research
• #germplasm

Evaluation of the Activity of Insecticides Plants in the Far North Region of Cameroon

Sadou Ismaël, Noé Woïn, Richard Ghogomu, MBONGAYA Samy Eware

International Journal of Environment Agriculture and Biotechnology

This study proposes to assess the activity of insecticide plants in the far North region of Cameroon. The leaves or bark of four local plants (Azadirachtaindica, Boswelliadalzeilii, Khayasenegalensis and Ocimumcanum) were harvested, dried and powdered for the formulation of insecticidal chopsticks at different doses. Toxicity tests have been conducted on adult culicidae mosquitoes by fumigation. They reveal low levels of mortality after 15 minutes of exposure to the smoke of the chopsticks. Remanence due to chopsticks smoke leads to high rates of mortality after 6 and 24 hours of exposure. Mortality rates increase with the dose of each vegetable powder. Lethal doses were calculated 6 hours after exposure for each plant powder. Those of the leaves of Azadirachtaindica proved to be the most efficient thus with the lowest LD50 value of 36.14%. These vegetable powders can be used as natural insecticides instead of chemical insecticides.

• #insect pest control strategies
• #agricultural pest management studies
• #insect resistance and genetics
• #toxicology

Inventaire Des Insectes Ravageurs et Vecteurs du Virus De La Panachure Jaune du Riz Dans Les Ecosystemes Rizicoles De La Region De L'extreme-nord du Cameroun

I. Sadou, Noé Woïn, Richard Ghogomu, Et Hamasselbe Aboubakar

Insect vectors of the Rice Yellow Mottle Virus (RYMV) were studied in 2010 in the major irrigated rice ecosystems of Maga and Yagoua and in upland rice fields of Maroua in the Far-North province of Cameroon. Sampling of the insects vectors was carried out every forth night in upland rice fields and irrigated rice fields using a special sweep net and a D-VAC. From the samples collected in the various sites, the population of dominant insect vector, were analysed in relation to the phenological stage of the rice plant. The diversity and the frequency of the major groups of potential predators and parasitoids were also analysed. The following vectors of the Rice Yellow Mottle Virus were identified at different stages of growth of rice in irrigated rice fields and in upland rice fields: Chnootriba similis (Coleoptera: Coccinellidae), Chaetocnema pulla (Coleoptera: Chrysomelidae), Trichispa sericea (Coleoptera: Chrysomelidae), Locris rubra (Hemiptera: Cicadellidae), Nephotettix nigropictus (Hemiptera: Cicadellidae), Sogatella furcifera (Hemiptera: Delphacidae), Cofana spectra (Hemiptera: Cicadellidae), Recilia dorsalis (Hemiptera: Cicadellidae), Niparvata lugens (Hemiptera: Delphacidae) and Diopsis thoracica (Diptera: Diopsidae). The populaton size of these vectors was particularly important at the vegetative stages of the rice plant. The irrigated rice ecosystems were infested mainly by the insect vector of the Rice Yellow Mottle Virus. Nephotettix nigropictus (Hemiptera: Cicadellidae) which was the most abundant specie was collected at the vegetative stages of growth of the upland and irrigated rice fields. The predators sampled in the field included: Araneus sp. (Araneae: Araneidae), Tetragnatha sp. (Araneae: Tetragnatidae), Pardosa injucunda (Araneae: Lyconidae), Xanthadalia effusa (Coleoptera: Coccinellidae). The parasitoids that were sampled included Hydrellia griseola (Diptera: Ephydridae), Bracon sp. (Hymenoptera: Braconidae), Xiphosomella sp. (Hymenoptera: Braconidae) and Platygaster sp. (Hymenoptera: Platygasteridae). The parasitoid Hydrellia griseola (Diptera: Ephydridae) and the predator Araneus sp. (Araneae: Araneidae) were the most abundant natural enemies of the insect vector in upland rice fields in Maroua and irrigated rice fields in Maga and Yagoua.

• #dengue and mosquito control research
• #insect resistance and genetics
• #agricultural research and practices
• #biology

Sensibilité de 23 variétés de haricot commun aux bruches

Edwige Djomaha, Richard Ghogomu

La conservation des produits vivriers en general, du haricot en particulier pose de serieux problemes dans les milieux tropicaux a causes des charancons (bruches). Les temperatures et humidites elevees favorisent leur developpement. Les pertes sont enormes allant jusqu'a 100% si aucun traitement n'est fait. Plusieurs methodes de lutte sont preconisees notamment l'utilisatuion des insecticides. Malheureusement cette methode presente des inconvenients sur la sante humaine, l'environnement. Une solution locale peut couteuse et accessible a tous c'est le choix des varietes resistantes disponibles aupres des paysans.

• #insect-plant interactions and control
• #horticultural and viticultural research
• #plant physiology and cultivation studies
• #humanities

Esterase‐mediated resistance to pyrethroids in field populations of Helicoverpa armigera (Lepidoptera: Noctuidae) from Central Africa

Joseph Achaleke, Thibaud Martin, Richard Ghogomu, Maurice Vaissayre, Thierry Brévault

Pest Management Science

BACKGROUND: Evolution of pyrethroid resistance in the cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) threatens continued cotton production in Central Africa. Dose-response bioassays were conducted on area-wide collection of bollworm populations from major host plants, while biochemical techniques were used to evaluate basic mechanisms underlying resistance. RESULTS: Pyrethroid resistance is primarily associated with detoxification by enhanced esterase activity. High resistance to cypermethrin (RF = 67-1771), cross-resistance to deltamethrin (RF = 60-2972) and lack of cross-resistance to the non-ester pyrethroid etofenprox (RF = 2-10) were observed among H. armigera field populations and laboratory-selected strains. Enzymatic assays showed that esterase activity, but not oxidase content or glutathione-S-transferase activity, was positively correlated with resistance to cypermethrin. Pretreatment with piperonyl butoxide (PBO) resulted in significant synergism with cypermethrin in 6/10 field populations, but not in the laboratory-selected strain, indicating that additional mechanisms such as mixed-function oxidase (MFO) may be involved in field resistance. The absence of cross-resistance to DDT ruled out a possible target-site modification. CONCLUSION: Knowledge of the mechanisms involved in pyrethroid resistance and the lack of cross-resistance to spinosad and indoxacarb is a key to devising new resistance management strategies aimed at restoring the efficacy of pyrethroid-based programmes.

• #insect resistance and genetics
• #insect-plant interactions and control
• #viral infectious diseases and gene expression in insects
• #helicoverpa armigera

First Central African PAGES Workshop

Richard Ghogomu

PAGES news

2007 at the University of Yaounde I, Cameroon. This three-day gathering was designed to bring together paleoscientists, researchers, teachers, stakeholders, and decision/policy makers, with the goal of encouraging research collaboration and capacity building, and attempting to close the gap between policy and research in paleoscience and global change. The workshop attracted over 70 participants from the Central African subregion and beyond. Broadly defi ned, Central Africa embraces that part of the continent that straddles both sides of the equator for about 15 o and is drained largely by the Congo River system (Fig. It has a wide range of ecosystems varying from mangroves at the coastlines through tropical rainforest at the equator to grassland savannah and Soudano-Sahelian types towards the north. Central Africa has a population of over 100 million with one of the highest annual population increases (2.4-3.5%) in the world. Natural (landslides, volcanic eruption) and human-induced disasters (drought, desertifi cation, fl ood, epidemics and refugees) are frequent and on the rise.

• #aquatic ecosystems and biodiversity
• #science and climate studies
• #african botany and ecology studies
• #library science