Potential of the predatory mite, Amblyseius swirskii to suppress the broad mite, Polyphagotarsonemus latus on the gboma eggplant, Solanum macrocarpon

In Benin, the tarsonemid mite Polyphagotarsonemus latus (Banks) (Prostigmata: Tarsonemidae) is a key pest of gboma eggplant Solanum macrocarpon (L.) (Solanales: Solanaceae), a leafy vegetable on which it causes considerable damage to the plants and substantial reduction in yield. Predatory mites in the family Phytoseiidae have been successfully used in the biological control of numerous agricultural pests worldwide. In that respect, a population of the phytoseiid mite Amblyseius swirskii (Athias-Henriot) (Mesostigmata: Phytoseiidae) has been identified as a potential predator of P. latus, and is now a candidate for release against this pest in Benin. The objective of the present study is to determine, through laboratory experiments, the predation rate and life table parameters of A. swirskii when feeding on P. latus or alternative food such as maize pollen. Under laboratory conditions the mean number of P. latus consumed by A. swirskii, and daily oviposition, significantly increased as the number of prey increased. Total development time of A. swirskii was significantly shorter when it fed on P. latus than on maize pollen. Net reproduction rate, intrinsic rate of increase, mean generation time and the finite rate of increase of A. swirskii were were all significantly lower on P. latus than on maize pollen. However, doubling time was significantly higher on maize pollen. This study shows that A. swirskii is a good predator of P. latus, and that maize pollen can efficiently sustain A. swirskii populations when P. latus densities on plants become low. Consequently, A. swirskii can be used for the biological control of the broad mite P. latus on gboma eggplant, and on other solanaceous crops in Benin and elsewhere

The predatory mite Typhlodromalus aripo prefers greenmite induced plant odours from pubescent cassava varieties

Article PurchasedIt is well known that plant-inhabiting predators use herbivore-induced plant volatiles to locate herbivores being their prey. Much less known, however, is the phenomenon that genotypes of the same host plant species vary in the attractiveness of these induced chemical signals, whereas they also differ in characteristics that affect the predator’s foraging success, such as leaf pubescence. In a series of two-choice experiments (using a Y-tube olfactometer) we determined the preference of Typhlodromalus aripo for pubescent versus glabrous cassava cultivars infested with the cassava green mite Mononychellus tanajoa and also the preference for cultivars within each of the two groups. We found that when offered a choice between pubescent and glabrous cassava cultivars (either apex or leaves), T. aripo was significantly more attracted to pubescent cultivars. For each cultivar, M. tanajoa infested leaves and apices were equally attractive to T. aripo. There was however some variation in the response of T. aripo to M. tanajoa-infested plant parts within the group of pubescent cultivars, as well as within the group of glabrous cultivars. Our study confirms not only that T. aripo uses herbivore-induced plant volatiles to search for prey in cassava fields, but it also shows that it can discriminate between glabrous and pubescent cultivars and prefers the latter. This knowledge can be useful in selecting cultivars that are attractive and suitable to T. aripo, which, in turn, may promote biological control of the cassava green mite

Vulnérabilité des cossettes issues de quelques cultivars d’igname à l’attaque de Dinoderus porcellus Lesne (Coleoptera: Bostrichidae) en conditions de laboratoire

Dinoderus porcellus Lesne a été récemment identifié comme un véritable ravageur des stocks de cossettes d’igname en Afrique de l’Ouest. En conséquence, plusieurs méthodes de lutte ont été testées ou envisagées contre ce ravageur et comprennent, entre autres, l’utilisation des cultivars d’ignames résistants à l’insecte. Dans la présente étude, le comportement de quatre lots de cossettes issues des quatre cultivars d’igname suivants : Otoukpanan, Singor, Kprakpra et Portchahabim face à D. porcellus a été observé et comparé. Cette série d’études a porté sur : (1) la préférence de D. porcellus pour l’un ou l’autre des quatre cultivars; (2) la vitesse de développement et le taux d’émergence de D. porcellus sur ces différents cultivars d’igname, et (3) leur susceptibilité à travers les dégâts et l’effectif de la progéniture de D. porcellus enregistrés sur chacun d’eux. Nos résultats ont montré : que D. porcellus a une préférence marquée pour les cossettes de Otoukpanan suivi de Singor, Portchahabim et enfin Kprakpra ; qu’il s’est développé plus rapidement sur Otoukpanan suivi de Singor, Portchahabim et Kprakpra ; et qu’il a causé le plus de dégâts sur Otoukpanan sur lequel sa progéniture a été également la plus abondante. Portchahabim et Singor ont été les cultivars les moins attaqués du lot ; de plus, aucune progéniture n’a été enregistrée sur Portchahabim. Ainsi donc, les cultivars Singor et Portchahabim ont été les moins vulnérables aux attaques de D. porcellus et devraient être privilégiés dans la préparation des cossettes.Mots clés: Dioscorea sp., insectes des denrées stockées, préférence, résistance variétale, Bénin

Interactions between the predatory mite Typhlodromalus aripo and the entomopathogenic fungus Neozygites tanajoae and consequences for the suppression of their shared prey/host Mononychellus tanajoa

Published online: 28 October 2012The predatory mite Typhlodromalus aripo and the entomopathogenic fungus Neozygites tanajoae, both introduced from Brazil for control of the cassava green mite (CGM) Mononychellus tanajoa, now co-occur in cassava fields in Benin. However, studies on interactions between these two natural enemies and how they might affect CGM biological control are lacking. We determined in screenhouse experiments the effects of single and combined releases of N. tanajoae and T. aripo on CGM suppression. In the single natural enemy treatment, both T. aripo and N. tanajoae significantly reduced CGM densities, but the results of the predator (T. aripo) are more quickly measurable than those of the pathogen (N. tanajoae) in our short-term experiment. The level of CGM suppression in the combined natural enemy treatment was reduced considerably compared with T. aripoalone, but only slightly when compared with N. tanajoae alone, with a simultaneous reduction in T. aripo and N. tanajoae abundance or prevalence. In a laboratory experiment, T. aripo fed more on N. tanajoae-infected CGM than on healthy CGM and its oviposition and survival were reduced when fed on the former compared with the latter, which can help in explaining the reduction in numbers of T. aripo and consequently the considerable loss in suppression of CGM in the combined natural enemy treatment in the screenhouse experiment. Together, the screenhouse and the laboratory experiments predicted negative interactions between the two natural enemies with negative consequences for CGM biological control. Long-term field observations and rigorous field experiments that simultaneously manipulate T. aripo and N. tanajoae abundance and prevalence are needed to validate the prediction of this study

Potentialités de l’acarien prédateur Amblyseius swirskii (Athias-Henriot) (Acari: Phytoséiidae) dans la lutte biologique contre la mouche blanche Bemisia tabaci (Genn.), vecteur de la mosaïque du manioc en Afrique

La mosaïque africaine du manioc est une maladie redoutable qui ravage les champs de manioc en Afrique. Elle est causée par un virus dont le vecteur principal est la mouche blanche Bemisia tabaci. Un des moyens de lutte contre cette maladie passe par la lutte contre le vecteur B. tabaci, réputé très résistant aux insecticides chimiques. L’acarien prédateur phytoséiide Amblyseius swirskii a été identifié en Europe comme un potentiel prédateur de B. tabaci. Dans une série d’études au laboratoire nous avons déterminé la capacité de deux populations (israélienne et béninoise) de A. swirskii à contrôler les populations de B. tabaci, réduisantainsi l’incidence de la mosaïque sur les plants de manioc. Pour chacune des deux populations du prédateur, les taux de prédation, d’oviposition et de survie des femelles adultes nourries aux larves de premier stade de B.tabaci, en présence ou en absence de pollen de maïs, étaient très faibles par rapport à ceux obtenus dans des études précédentes avec du pollen de la massette, Typha australis ou du maïs. Aussi, les paramètresbiologiques démographiques montrent que sur les larves de B. tabaci le niveau de population de A. swirskii a décru très rapidement pour s’annuler, attestant que B. tabaci n’est pas une proie idéale pour le prédateur. Autotal, ces résultats indiquent que A. swirskii ne serait pas un bon agent de lutte biologique contre B. tabaci sur les plants de manioc en Afrique.Mots clés : Manihot esculenta, aleurode, Aleyrodidae, paramètres démographiques, supplément nutritif

Insect fauna associated with Anacardium occidentale (Sapindales: Anacardiaceae) in Benin, West Africa

First published online: 1 January 2014Cashew, Anacardium occidentale L. (Sapindales: Anacardiaceae), is an important cash crop in Benin. However, its production is threatened by several biotic factors, especially insects. In Benin, very few studies have focused on insects and just listed species commonly found on cashew worldwide. The present investigation fills this gap by presenting an exhaustive inventory of insect species associated with this crop in the country. The survey was carried out from September 2009 to August 2010 in 22 cashew orchards (5 young and 17 mature) distributed over three major agroecological zones where cashew is most produced in the country. Insects were collected using chemical knock-down technique and visual observation followed by capture with sweep net. In addition, infested plant organs were sampled and incubated to collect emerging insects. In total, 262 insect species were recorded and identified. Among them, the wood borer Apate terebrans Pallas, the leafminer Eteoryctis gemoniella Stainton, and the mirid bugs Helopeltis schoutedeni Reuter., and Helopeltis anacardii Miller., appeared as the most important insect species attacking cashew in Benin. Beneficial insects encountered included some predators, parasitoids, and pollinators. Few vertebrate predators were also recorded on the trees. Differences in agroecological conditions or in field cleanliness did not affect the number of insect species encountered in the cashew orchards. The results of this study represent an important baseline data for the design and implementation of strategies for cashew protection in Benin

Comparative Effects of Some Botanical Extracts and Chemicals in Controlling the Red Spider Mite Tetranychus evansi Baker & Pritchard on Solanaceous Crops

The tomato red spider mite, Tetranychus evansi, is an invasive pest reported on solanaceous crops in Benin around 2008, causing heavy economic damage. The control of this mite by farmers is mainly done through intensive applications of chemical pesticides that are not always effective. In the present study, we evaluated in a laboratory, at IITA-Benin, the effects of two botanical insecticides: the Cashew Nut Shell Liquid (CNSL) and Neem oil. This is together with Acarius 18 EC, a chemical acaricide generally used by growers on eggs and adult females T. evansi. The half recommended dose (0.5 l/ha), the recommended dose (1 l/ha), and the double recommended dose (2 l/ha) of Acarius and Neem oil as well as solutions at 1%, 2 %, 3%, 4% and 5% of CNSL were tested. Mean egg hatching rates varied significantly among treatments, ranging from 0.00 ± 0.00% (Neem oil and CNSL) (respectively at half recommended dose and 4%) to 100% (Control). Mortality of adult female T. evansi also differed significantly among treatments (P < 0.0001), ranging from 22.00 ± 4.20% to 100%. The highest mortality rates were recorded with Neem oil at any doses and with CNSL at 4%, whereas the lowest rate was recorded with the control treatment. Fecundity of pesticide-treated females T. evansi and proportion of eggs that hatched revealed significant differences among all doses of products (P < 0.0001). It appears from this study that even the half recommended dose of Neem oil and the CNSL at 4% were very effective on suppressing T. evansi populations and should, therefore, be subject to further studies to test their compatibility with natural enemies, and to determine strategies for their efficient applications in greenhouse and under field conditions.   &nbsp

Re-assessing the pest status of Tetranychus evansi (Acari: Tetranychidae) on solanaceous crops and farmers control practices in Benin

Open Access Journal; Published online: 24 Sep 2022This study was carried out 7 years after a first one conducted in 2013 as part of the policy of the Benin government to promote the vegetable production sector. Data collection was mostly based on a countrywide survey conducted in 25 municipalities throughout Benin, from August to December 2020. Farmers were selected based on their experience in cultivating solanaceous crops, and were interviewed to assess their perception about the severity of the spider mite Tetranychus evansi, the control method they used against this pest, and their knowledge about potential predators associated with the mites. Additionally, predatory mites associated with T. evansi in farmer fields were identified. All farmers recognized T. evansi to which they attributed local names depending on their ethnic group. They were also able to identify its damages on solanaceous crops. They indicated that outbreaks of T. evansi occurs at the end of the rainy season while their damages are more severe during the dry season. Production losses due to the mites were estimated by farmers to 27%, 24% and 22% respectively for tomato, African eggplant, pepper in the moderate damage case and 80%, 79%, 55% respectively for tomato, African eggplant and pepper in the severe damage conditions. To fight the mites, farmers generally apply heavy doses of chemical pesticides at high frequency. Pyrethroid and organophosphate compounds are the most frequently used pesticides. The only phytophagous mite recorded was T. evansi. A total of four species of predatory mites, all belonging to the phytoseiid family, were found associated with the pest on Solanaceous plants: Amblyseius swirskii, A. tamatavensis, Neoseiulus barkeri and N. longispinosus. This is the first report of the presence of N. longispinosus in Benin. Considering the high losses attributed to the pest, effective and sustainable management practices are necessary

Breeding maize (Zea mays) for striga resistance: past, current and prospects in sub-Saharan Africa

Open Access Article; Published online: 01 Mar 2021Striga hermonthica, causes up to 100% yield loss in maize production in Sub‐Saharan Africa. Developing Striga‐resistant maize cultivars could be a major component of integrated Striga management strategies. This paper presents a comprehensive overview of maize breeding activities related to Striga resistance and its management. Scientific surveys have revealed that conventional breeding strategies have been used more than molecular breeding strategies in maize improvement for Striga resistance. Striga resistance genes are still under study in the International Institute for Tropical Agriculture (IITA) maize breeding programme. There is also a need to discover QTL and molecular markers associated with such genes to improve Striga resistance in maize. Marker Assistance Breeding is expected to increase maize breeding efficiency with complex traits such as resistance towards Striga because of the complex nature of the host‐parasite relationship and its intersection with other environmental factors. Conventional alongside molecular tools and technical controls are promising methods to effectively assess Striga in Sub‐Saharan Africa