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 20–30C. 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 arasitization 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 24–28C. For the host M. vitrata, rm was maximal at temperatures of 26–30C. The data are discussed in the context of the potential of A. taragamae for biological control of M. vitrata

Influence of plant and residue age on attraction, acceptance and larval survival of the banana weevil Cosmopolites sordidus (Coleoptera: Curculionidae)

Laboratory trials were conducted in Uganda at the Kawanda Agricultural Research Institute to determine attraction, eclosion success and larval survivorship of the banana weevil Cosmopolites sordidus (Germar) on crop residues of different ages. In the first experiment, studies focused on different types and ages of residues of one susceptible highland banana clone ‘Nabusa’ (genome group AAA-EA). Corms attracted 65% of the test weevils, pseudostems 30%, while 5% were non-respondents. Oviposition levels and the number of eggs per female were higher on young than old corms. Eclosion rates of 30 DAH. To assess immature survival, 30 DAH. Larval duration and mean days taken for adult emergence increased with plant and crop residue age. Females emerging from the different plant and residues treatments were similar in weight. The data suggest that all aged residues are suitable hosts for C. sordidus, suggesting that sanitation practices should be implemented soon after harvest

Assessing nontarget effects and host feeding of the exotic parasitoid Apanteles taragamae, a potential biological control agent of the cowpea pod borer Maruca vitrata

Article PurchasedApanteles taragamae Viereck is a larval parasitoid introduced in Benin for classical biological control of the cowpea pod borer Maruca vitrata Fabricius. In the laboratory, we evaluated the effects of A. taragamae on non-target herbivore species, and on another parasitoid of M. vitrata, i.e. the egg-larval parasitoid Phanerotoma leucobasis Kriechbaumer. Furthermore, we addressed the host feeding behaviour of A. taragamae. The host specificity of A. taragamae was assessed by offering six other lepidopteran species to the wasp. The competitive ability of A. taragamae was studied by providing the wasp with one- and two-days-old M. vitrata larvae that had hatched from eggs previously parasitized by P. leucobasis. Controls consisted of eggs and larvae offered only to P. leucobasis and A. taragamae, respectively. None of the other six lepidopteran species was successfully parasitized by A. taragamae. The larval parasitoid A. taragamae outcompeted the egg-larval parasitoid P. leucobasis when offered two-days-old host larvae. Competition between the two parasitoid species did not significantly affect one-day-old host larvae that were less suitable to A. taragamae. Host feeding by A. taragamae did not affect survival of one-day-old or two-days-old M. vitrata larvae. However, the percentage parasitism of two-days-old larvae was significantly reduced when exposed to female A. taragamae wasps that had been starved during 48 h. The data are discussed with regard to host specificity, host feeding patterns and to factors underlying the outcome of intrinsic competition between parasitoid species

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

Open Access JournalThe 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

Acetate ligands determine the crystal structure of CdSe nanoplatelets - a density functional theory study.

Cadmium selenide (CdSe) nanoplatelets of a few atomic layers thick exhibit extremely sharp photoluminescence peaks and are synthesized in the zinc blende crystal structure, whereas the most stable bulk polymorph of CdSe is the wurtzite structure. These platelets can be synthesized very monodispersely in thickness, and are covered with acetate ligands. Here, we show by means of density functional theory (DFT) calculations that these ligands play a pivoting role in the stabilization of 2D nanosheets as a whole, including the deviating crystal structure. The relative stability as a function of slab thickness, strong effects on electronic properties, and implications for synthesis are discussed.The Dutch science foundation NWO : a VIDI grant (grant number 723.012.006)

Effect of age, female mating status and density on the banana weevil response to aggregation pheromone

The banana ( Musa spp.) weevil ( Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) is a major pest in East Africa causing yield losses of up to 14 metric tonnes per hectare annually. Laboratory and field experiments were conducted to determine whether the response of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) to its aggregation pheromone was influenced by age, female mating status and weevil density. Laboratory bioassays were conducted using a double pitfall olfactometer, while a bucket pitfall trap was used in field experiments. There was no significant (P>0.05) difference in response to pheromone between immature and mature weevils (males and females) in laboratory bioassays. Forty-day-old weevils had a stronger response to the pheromone than 10-day-old ones under field conditions. The response of unmated weevils to the pheromone was stronger than that of mated weevils, both in the laboratory and field. The percentage of unmated and mated weevils recaptured from 0 and 3 m were similar but significantly different from 6 m way from the pheromone baited trap. The response of the weevils to the pheromone was not significantly (P>0.05) influenced by its previous density

Biosignal and context monitoring: Distributed multimedia applications of body area networks in healthcare

We are investigating the use of Body Area Networks (BANs), wearable sensors and wireless communications for measuring, processing, transmission, interpretation and display of biosignals. The goal is to provide telemonitoring and teletreatment services for patients. The remote health professional can view a multimedia display which includes graphical and numerical representation of patients’ biosignals. Addition of feedback-control enables teletreatment services; teletreatment can be delivered to the patient via multiple modalities including tactile, text, auditory and visual. We describe the health BAN and a generic mobile health service platform and two context aware applications. The epilepsy application illustrates processing and interpretation of multi-source, multimedia BAN data. The chronic pain application illustrates multi-modal feedback and treatment, with patients able to view their own biosignals on their handheld device

Effect of mulching on banana weevil movement relative to pheromone traps

Banana weevil (Cosmopolites sordidus) is a major pest in East Africa causing yield losses of up to 14 metric tonnes per hectare annually. A study was conducted in Uganda to determine the effect of mulching on banana (Musa spp. L.) weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), movement relative to pheromone-baited traps. Three treatments were used to create different mulching levels: banana without mulch (control), banana with thin mulch (< 6 cm thick), and banana with thick mulch (15 cm thick). Pheromone trapswere placed in the plots and weevil trap catches were monitored. Weevil catches in pheromone traps from both mulched and unmulched plots were generally similar. The mulching level had no effect on the ratio of males to females recaptured. The numbers of weevils captured in pheromone traps were lower than in the wet season andwas not influenced by mulch levels. Mulching levels had a limited influence on the numbers of weevils recaptured from different directions. The results generally indicate that mulching has no effect on weevil catches in pheromone traps

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Whereas bulk zinc oxide (ZnO) exhibits the wurtzite crystal structure, nanoscale ZnO was recently synthesized in the rock salt structure by addition of Mg. Using first-principles methods, we investigated two stabilization routes for accessing rock salt ZnO. The first route is stabilization by Mg addition, which was investigated by considering ZnO-MgO mixed phases. The second route is through size effects, as surface energies become dominant for small nanocrystal sizes. We discovered that the surface energy of rock salt ZnO is surprisingly low at 0.63 J m-2, which is lower than those of wurtzite and zinc blende ZnO and lower than that of rock salt MgO. We predict that pure rock salt ZnO is stable for nanocrystals smaller than 1.6 nm, and that Mg additions can greatly extend the size range in which the rock salt phase is stable. Both mixed-phase and core-shell models were considered in the calculations. The present approach could be applied to predict the stabilization of many other nanocrystal phases in deviating crystal structures