Elie Ayitondji Dannon

Functional response and life history parameters of Apanteles taragamae, a larval parasitoid of Maruca vitrata

The legume pod borer Maruca vitrata Fabricius (Lepidoptera: Crambidae) is a serious pest of cowpea in West-Africa. The parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) that originates from Taiwan is a potential candidate for biological control of M. vitrata. We investigated under laboratory conditions the functional response of the parasitoid by offering each experienced female 10, 20, 30 and 40 larvae of M. vitrata. We studied the influence of different host larval ages on the development, longevity, sex ratio, lifetime fecundity and parasitization rate of the wasp. In a comparative study, we also investigated the life history of A. taragamae and M. vitrata at different temperatures in the range of 20–30°C. The parasitoid successfully parasitized two- and three-day-old host larvae (first and second instars). Younger larvae (one-day-old) were parasitized to a lesser extent, and only males developed in them. Older larvae were not parasitized, partly because of defensive host behaviour. The success of parasitization was positively correlated with the density of two-day-old M. vitrata larvae. Parasitoid developmental time and longevity decreased with increasing temperature. The intrinsic rate of population increase (rm) exhibited an optimum curve with a maximum at 24–28°C. For the host M. vitrata, rm was maximal at temperatures of 26–30°C. The data are discussed in the context of the potential of A. taragamae for biological control of M. vitrata.

Effects of Volatiles from Maruca vitrata Larvae and Caterpillar-Infested Flowers of Their Host Plant Vigna unguiculata on the Foraging Behavior of the Parasitoid Apanteles taragamae

The parasitoid wasp Apanteles taragamae is a promising candidate for the biological control of the legume pod borer Maruca vitrata, which recently has been introduced into Benin. The effects of volatiles from cowpea and peabush flowers and Maruca vitrata larvae on host selection behavior of the parasitoid Apanteles taragamae were investigated under laboratory conditions by using a Y-tube olfactometer. Naïve and oviposition-experienced female wasps were given a choice between several odor sources that included (1) uninfested, (2) Maruca vitrata-infested, and (3) mechanically damaged cowpea flowers, as well as (4) stem portions of peabush plants carrying leaves and flowers, (5) healthy M. vitrata larvae, and moribund (6), and live (7) virus-infected M. vitrata larvae. Responses of naïve and oviposition-experienced female wasps did not differ for any of the odor source combinations. Wasps were significantly attracted to floral volatiles produced by cowpea flowers that had been infested with M. vitrata larvae and from which the larvae had been removed. Apanteles taragamae females also were attracted to Maruca vitrata-infested flowers after removal of both the larvae and their feces. Female wasps discriminated between volatiles from previously infested flowers and mechanically damaged flowers. Uninfested cowpea flowers attracted only oviposition-experienced wasps that had received a rewarding experience (i.e. the parasitization of two M. vitrata larvae feeding on cowpea flowers) before the olfactometer test. Wasps also were attracted to uninfested leaves and flowers of peabush. Moreover, they were also attracted to healthy and live virus-infected M. vitrata larvae, but not when the latter were moribund. Our data show that, similarly to what has been extensively been reported for foliar volatiles, flowers of plants also emit parasitoid-attracting volatiles in response to being infested with an herbivore.

An assessment of learning gains from educational animated videos versus traditional extension presentations among farmers in Benin

ABSTRACT This study compared the efficacy of linguistically and dialectically localized animated educational videos (LAV) against traditional learning extension (TLE) presentations for learning gains of knowledge around agricultural- and healthcare-related topics within a rural population in Benin. While both approaches demonstrated learning gains, LAV resulted in significantly higher test scores and more detailed knowledge retention. A key contribution of this research, moreover, involves the use of mobile phone technologies to further disseminate educational information. That is, a majority of participants expressed both a preference for the LAV teaching approach and a heightened interest in digitally sharing the information from the educational animations with others. Because the animations are, by design, readily accessible to mobile phones via Africa’s explosively expanding digital infrastructure, this heightened interest in sharing the animated videos also transforms each study participant into a potential a learning node and point of dissemination for the educational video’s material as well.

Effect of Maruca vitrata (Lepidoptera: Crambidae) host plants on life‐history parameters of the parasitoid Apanteles taragamae (Hymenoptera: Braconidae)

Abstract  The effect of four host plant species of the herbivore Maruca vitrata Fabricius (Lepidoptera: Crambidae) on development time, longevity, fecundity and sex ratio of the parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) was investigated under laboratory conditions. The larvae were parasitized when in the second instar. Maruca vitrata larvae were fed with flowers of four legumes, that is, Vigna unguiculata (cowpea), Sesbania rostrata, Lonchocarpus sericeus and Pterocarpus santalinoides, or an artificial diet both before and after parasitization. The parasitoid did not develop in hosts feeding on L. sericeus or V. unguiculata at 25°C, or on P. santalinoides at 25°C or 29°C. Apanteles taragamae had the shortest development time on artificial diet at both 25°C and 29°C while the longest development time was recorded on L. sericeus at 29°C. Female wasps took longer to develop compared to males at the two temperatures, regardless of the feeding substrate of their host. The longevity of the wasps at 25°C varied among feeding substrates, but not at 29°C. Survival rate of parasitized larvae depends on the feeding substrate. Moreover, infection of host larvae with Maruca vitrata multi‐nucleopolyhedrovirus (MaviMNPV) killed larger proportions of parasitized larvae at 25°C than at 29°C, which was likely caused by the difference in parasitoid developmental rate. The proportion of female parasitoids was lowest on L. sericeus. The daily fecundity showed a nonlinear trend regardless of the feeding substrate, indicating that A. taragamae is a pro‐ovigenic species. The data support the slow growth–high mortality hypothesis.

Interaction between the aphid parasitoid Lysiphlebus testaceipes (Hymenoptera: Aphidiidae) and its hyperparasitoid Syrphophagus africanus (Hymenoptera: Encyrtidae)

The interactions between the cowpea aphid Aphis craccivora Koch, its parasitoid Lysiphlebus testaceipes Cresson and hyperparasitoid Syrphophagus africanus Gahan were assessed in the laboratory. Host age preference for hyperparasitism was evaluated using parasitized aphids of different ages (i.e. 1, 2, 3, 4, 5 and 6 days old and mixed ages). We studied the influence of the hyperparasitoid on the parasitism efficiency of L. testaceipes, the effect of host age on some biological parameters of S. africanus, and its hyperparasitism based on aggregated or isolated mummies. The presence of S. africanus significantly affected aphid parasitism by L. testaceipes (21.2 ± 3.6 vs 36.6 ± 4.5%). Except for 1-day-old hosts, S. africanus successfully parasitized hosts of all tested ages, with preference for newly formed mummies (39.16 ± 3.31% parasitism in 5-day-old hosts). The development time of immature stages of the S. africanus progeny was significantly affected by host age. The sex ratio of the hyperparasitoid progeny was largely female biased and did not vary with host age. Syrphophagus africanus females from live parasitized aphids produced more offspring (36.55 ± 6.28 vs 25.00 ± 7.16) and lived longer (21.09 ± 1.57 vs 10.88 ± 2.31 days) than those from mummy hosts. Hyperparasitism rates were higher on aggregated mummies than on dispersed ones (36.00 ± 2.86 vs 20.66 ± 4.00%).

Repellent Effect and Insecticidal Activities of Bridelia ferruginea, Blighia sapida, and Khaya senegalensis Leaves Powders and Extracts against Dinoderus porcellus in Infested Dried Yam Chips

Dinoderus porcellus is considered as the most important pest of stored yam chips and compounds extracted from plants can be used for its control. The present study aimed to test the insecticidal and repellent activities of powders and extracts of leaves of Bridelia ferruginea, Blighia sapida, and Khaya senegalensis against D. porcellus. The efficacy of plant powders was compared with the synthetic pesticide Antouka (Permethrin 3 g/kg + pirimiphos 16 g/kg). The results of the experiment revealed that all plant powders were effective as repellents. Antouka was more effective as insecticidal than the plant powders and minimal weight loss was observed with B. sapida at 2%. Among treatments, propanol extract of K. senegalensis at 5% was found to elicit the highest repellent effect on D. porcellus. The LC50 results revealed that the acetone extract of K. senegalensis is the most toxic (0.29 μL/insect) to the pest, while the propanol extract of B. ferruginea at 5% exhibited strong fumigant toxicity against D. porcellus, with 88.89% of pest mortality at 160 μL/L air. The findings from the current work proved that plant powders and extracts of the three plants are sources of botanical insecticides which may be used in the integrated management of D. porcellus.

Influence of Rearing Substrates and Nontarget Hosts on the Bionomics of the Tachinid Parasitoid Nemorilla maculosa (Diptera: Tachinidae)

Abstract The tachinid Nemorilla maculosa Meigen (Diptera: Tachinidae) was introduced from Taiwan to Benin for evaluating its potential as a biocontrol candidate against the cowpea pest Maruca vitrata (Fabricius) (Lepidoptera: Crambidae). To optimize its rearing, we assessed the influence of M. vitrata larval age and rearing substrate—cowpea germinating grains and peabush leaves—on its life table parameters, while its host specificity was investigated with regard to nontarget effects. Parasitism rates were higher when older larvae (10- and 14-d old) were offered to females of N. maculosa compared to the younger (2-, 4-, and 6-d old) host larvae. Regardless of the rearing substrate, development time was longer for females than males, and females lived longer than males irrespective of the age of the host. Sex ratio did not vary significantly with host ages or rearing substrate. The average number of eggs laid by a female reared from M. vitrata larvae feeding on cowpea germinating grains or peabush leaves was 94.2 ± 4.38 and 71.9 ± 1.70 eggs, respectively. The host suitability of N. maculosa was assessed by testing four nontarget Lepidoptera species: Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae), Sesamia calamistis Hampson (Lepidoptera: Noctuidae), Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae), and Eldana saccharina Walker (Lepidoptera: Pyralidae). Larvae of S. littoralis and C. cephalonica were successfully parasitized while N. maculosa did not develop in the larvae of E. saccharina and S. calamistis although they were parasitized. Despite the potential of N. maculosa as a biological control agent against the pod borer M. vitrata, more detailed nontarget studies, extending to other native Crambidae species, are needed before making decisions on field releases.

The parasitic fly Nemorilla maculosa exploits host-plant volatiles to locate the legume pod borer, Maruca vitrata

Nemorilla maculosa Meigen (Diptera: Tachinidae) is a solitary endoparasitoid of the legume pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a key pest of cowpea, Vigna unguiculata (L.) Walp. (Fabaceae) in Africa. A colony of N. maculosa, introduced for experimental purposes from Taiwan to the laboratories of the International Institute of Tropical Agriculture (IITA) in Benin, was used for our studies. Olfactory reponses of N. maculosa to leaves of infested or uninfested cowpea and yellow peabush, Sesbania cannabina (Retz.) Pers. (Fabaceae), and to M. vitrata larvae were evaluated in a four‐arm olfactometer. For all combinations of odor sources, responses between naïve and oviposition‐experienced female flies did not differ. Nemorilla maculosa females were attracted by odors from uninfested leaves of yellow peabush and flowers of cowpea when compared with clean air, and they were attracted to plants damaged by M. vitrata with larvae removed. However, the female fly did not discriminate between odors from infested and uninfested plants. The parasitic fly N. maculosa proved well able to use volatile compounds from various host plants (peabush and cowpea) to locate its host, with a more pronounced attraction by the combination of host larvae and infested host plant parts. These findings are discussed in light of the prospective use of N. maculosa as a biological control agent against the legume pod borer.