Sélection de sites pour la conservation in situ des ignames sauvages apparentées aux ignames cultivées : cas de Dioscorea praehensilis au Bénin

Dioscorea praehensilis est une igname sauvage apparentée aux ignames cultivées du complexe D. cayenensis-D. rotundata qui évolue en populations naturelles dans les forêts du Sud et du Centre-Bénin. Pour identifier les sites propices à la préservation in situ de ses populations naturelles et de sa diversité génétique, six forêts du sud et du centre Bénin (Agoua, Ahozon, Ewè, Kétou, Lama et Niaouli) ont été prospectées. Les forêts de la Lama, d’Ewè et de Niaouli sont les plus riches en D. praehensilis avec, respectivement, des densités moyennes de 109, 63 et 59 pieds/ha. Type de végétation, éclairement, type de sol, pressions anthropiques et animales sont les facteurs qui influencent la densité de l’espèce dans les formations végétales prospectées et ont permis de repréciser son écologie. Sur la base de la densité de l’espèce et de son importance pour les populations riveraines, de l’importance de la pression anthropique et animale, du degré d’implication de la population dans la conservation des forêts, de la richesse des forêts en espèces de Dioscorea importantes ou rares, de l’état actuel de conservation de la forêt et de l’existence d'un plan d'aménagement, les forêts classées de la Lama et de Niaouli ont été identifiées comme les meilleurs sites pour la conservation in situ de D. praehensilis au Benin. Du fait de sa richesse secondaire en l’espèce D. burkilliana devenue très rare, la dotation de la forêt d’Ahozon d’un plan d’aménagement et de gestion participative a été proposée. © 2013 International Formulae Group. All rights reserved.Mots clés : Bénin, conservation, Dioscorea praehensilis, igname sauvage, forêts classée

Farmers knowledge, perceptions and management of Kersting’s groundnut (Macrotyloma geocarpum Harms) insect pests in Benin

Open Access JournalBackground Macrotyloma geocarpum Harms is a neglected and underutilized crop in Benin subject to several constraints including storage insect attacks, which contribute to the decrease in its production. An ethnobotanical survey using a semi-structured questionnaire was conducted in 15 villages in southern and central Benin to document farmers’ perceptions of M. geocarpum storage insect pests and their traditional management practices. Results The results showed that insect pest were the most important storage constraint of M. geocarpum. To overcome this constraint, the promotion of resistant landraces has been proposed by farmers. Six vernaculars names of storage insect pests of M. geocarpum were identified throughout the study area and all corresponding to Callosobruchus maculatus (F.) which proved to be the most abundant insect in the stocks. Palatability and fragility of seeds coat have been identified by farmers as the main factors favoring the infestation by this pest. Various storage containers of M. geocarpum have been inventoried. Our study revealed that education, storage containers, and Kersting’s groundnut landraces significantly influenced farmers’ perceptions of severity of insect pest damages. The use of chemicals and repellent plants were the main control methods used by farmers to protect stocks. Different levels of resistance of M. geocarpum landraces to storage insect pests were reported. Conclusions This study provides baseline information for development of integrated management approaches against storage insect pests of M. geocarpum. The perceived level of resistance to insect damage on Kersting’s groundnut landraces needs to be investigated

Termites (Blattodea: Termitidae) diversity and assemblages in different yam fields habitats in central Benin

Open Access JournalTermites are known to cause significant economic losses in yam fields. Therefore, assessing diversity and abundance of termites in yam fields is critical for their control. In this study, we compared the specific richness, abundance, and diversity of functional groups of termite pests in upland and lowland yam fields, across 15 villages using the standardized belt transect method. The specific termite diversity encountered in yam fields was compared with that of the Agoua classified forest. In general, eight genera classified into four subfamilies (Nasutitermitinae, Macrotermitinae, Amitermitinae and Coptotermitinae) grouped into two families (Termitidae and Rhinotermitidae) were identified. The highest number of the species (13) were identified in upland fields while the lowest number (10) were identified in the lowlands. Termite fauna collected from yam fields and from the Agoua forest were distinct, as showed by the similarity index. Amitermes evuncifer (Silvestri) was the most widely distributed and the most dominant termite species in upland yam fields while in lowland yam fields it was Macrotermes subhyalinus (Rambur). Three functional groups were observed with humus feeders only found in upland yam fields. Principal component analysis classified the 24 sampled transects into four groups with different termites feeding groups. The dominance of non-fungus-growers was observed in the groups mostly composed of transects in uplands yam fields. Three nesting habitats were represented (epigeal mound, wood, and subterranean). The results of this present research could help to develop efficient strategies against the identified key yam termite pests

Effect of population density on oviposition, development, and survival of Alloeocranum biannulipes (Hemiptera: Reduviidae) preying on Dinoderus porcellus (Coleoptera: Bostrichidae)

Open Access Journal; Published online: 19 Feb 2022Background Alloeocranum biannulipes Montr. and Sign.(Hemiptera: Reduviidae) is a predator present in stored yam chips and a promising biological control agent against Dinoderus porcellus Lesne (Coleoptera: Bostrichidae). Numerical responses of A. biannulipes to different densities (1, 2, 4, 6, and 8) of D. porcellus larvae were evaluated under ambient laboratory conditions (T°: 25 ± 2 °C; RH: 75–80%; photoperiod 12:12 h (L/D)). The number of consumed prey, duration of pre-oviposition and oviposition, number of eggs laid, pre-imaginal development times and mortality rate of the predator were recorded. Results The results revealed that A. biannulipes females preying on the highest larval density of D. porcellus (8) presented the highest predation rate (4.34 ± 0.18 larvae/predator/day), shortest pre-oviposition period (11.01 ± 0.57 days) and the highest oviposition period (15.83 ± 1.02 days). The daily number of eggs laid by A. biannulipes female (y) as a function of the number of D. porcellus larvae consumed (x) was modelled by the equation y = 0.158x2 – 0.4073x + 3.8151 (R2 = 0.571). The efficiency of prey conversion into eggs of A. biannulipes females decreased with increased prey density. The prey density did not affect the hatching rate of A. biannulipes eggs and the pre-imaginal development times. However, A. biannulipes nymphs fed with more (2 to 8) D. porcellus showed a significantly higher survival rate than those fed with a single larva. Conclusions The positive numerical response of A. biannulipes suggests that this predator could play a key role in biological control program against D. porcellus

Farmers' knowledge, perceptions and management practices for termite pests of maize in southern Benin

Open Access JournalTermite (Isoptera: Termitidae) infestation is an important constraint of maize production in Benin. A survey of 300 households was conducted in 2018 throughout 30 villages in Southern Benin to evaluate farmers’ knowledge, perceptions and management practices of maize termite pests using focus group discussions and individual interviews with a semi-structured questionnaire. The results showed that for most of the farmers, maize is the most susceptible crop to termite attacks and the maturation developmental stage having the highest termite abundance and damage. A total of 43 different names of maize termite pests corresponding to 8 species were recorded in the study area. Size and colour were the main criteria used by farmers to classify and identify maize termite pests. Amitermes evuncifer was perceived as the most damaging to maize during vegetative and maturation stages, while Macrotermes bellicosus was perceived by famers (32.5%) as most damaging during seedling and flowering maize development stages. Erratic rainfall was perceived by maize producers as the most important factor favouring termite infestation in maize fields. The majority of the local maize is considered by farmers as susceptible to termites. The use of synthetic insecticides was the main method to control termites. Four of the 20 pesticides used by farmers have active ingredients that have been listed as highly hazardous (class Ib) by the World Health Organization (WHO). Farmers training on the danger and impact of misuse of insecticides on the development of termite insecticide resistance was recommended. The development of an integrated termite management strategy is discussed and the future research for its implementation identified

Life table of the predator Alloeocranum biannulipes Montrouzier and Signoret (Hemiptera: Reduviidae) and a test of its ability to suppress populations of Dinoderus porcellus Lesne (Coleoptera: Bostrichidae) in stored yam chips

Published online: 30 Dec 2018Stored yam chips are attacked by Dinoderus porcellus Lesne, which can cause significant losses. The predator Alloeocranum biannulipes Montr. and Sign. is a potential biological control agent of D. porcellus. The biology, predation and mating behaviour of A. biannulipes were investigated under laboratory conditions. Moreover, the regulatory effect of this predator on population dynamics of D. porcellus, and hence on yam chips losses, were evaluated under both laboratory and natural conditions. Female A. biannulipes laid on average 42.1 ± 6.8 eggs, which hatched some 4.3 ± 0.3 d after laying, with a hatching rate of 86%. A total of five nymphal stages were recorded with a total nymphal period of 28.2 ± 0.1 d, and a total developmental period of 32.4 ± 2.3 d. Female A. biannulipes lived longer (29.3 ± 1.3 d) than did the males (25.8 ± 4.1 d). Periods of pre-oviposition, oviposition, and post-oviposition were 12.8 ± 1.7, 10.5 ± 1.0 and 5.3 ± 0.5 d, respectively. Life‐table analysis revealed an intrinsic rate of increase 0.29 females/day and a gross reproductive rate of 28.38 females/female. The predator A. biannulipes exhibited a ‘pin and jab’ mode of predation, and its mating behaviour consisted in sequential actions (excitation and approach, riding over, copulation and post-copulation). Under laboratory conditions, A. biannulipes significantly reduced the numbers of D. porcellus and the weight loss of yam chips after 8 weeks at the initial density of 10 predator for 20 preys. Similar trends were observed under farmer storage conditions; there was a significant reduction in the D. porcellus population and in weight loss of yam chips as compared to the control treatment after 8 and 12 weeks for all tested density prey/predator. Therefore, our findings showed that A. biannulipes can be mass reared under laboratory conditions and has the potential to be an effective biological agent against D. porcellus in stored yam chips