Responses of Bactrocera invadens (Diptera:Tephritidae) to Volatile Emissions of Fruits from Three Hosts

Bactrocera invadens is an invasive fruit fly species of Asian origin that was first detected in Kenya in 2003 and now has been reported in many parts of the African continent. The responses of B. invadens towards odour blends emitted from three host fruits, namely mango (Mangifera indica), marula (Sclerocarya birrea), and Indian almond (Terminalia catappa) growing in Nguruman and Embu in Kenya, were monitored in a dual choice olfactometer. Three mango varieties were tested (sensation, apple and kent), each at immature, mature unripe and ripe stages. Marula and Indian almond fruits were tested when mature, both when unripe and ripe. Results showed that, both male and female B. invadens were attracted equally to mature unripe and ripe mango fruits. However, in all cases attraction to immature fruits was significantly lower (P < 0.05). Two-way comparisons showed no significant difference between sensation and apple, but both attracted significantly more flies than kent. There were no significant different in attraction when M. indica, T. catappa and S. birrea were compared between each other. The results indicate that mature host fruits emit volatile constituents that are attractive to the fruit flies and if characterized may be useful in monitoring and managing B. invadens. Keywords: Bactrocera invadens, fruit hosts, attraction, 2-choice wind tunne

Unexpected diversity of Wolbachia associated with Bactrocera dorsalis (Diptera: Tephritidae) in Africa

Bactrocera dorsalis (Hendel) is an important pest of fruit-bearing plants in many countries worldwide. In Africa, this pest has spread rapidly and has become widely established since the first invasion report in 2003. Wolbachia is a vertically transmitted endosymbiont that can significantly influence aspects of the biology and, in particular, the reproduction of its host. In this study, we screened B. dorsalis specimens collected from several locations in Africa between 2005 and 2017 for Wolbachia using a PCR-based assay to target the Wolbachia surface protein wsp. Of the 357 individuals tested, 10 were positive for Wolbachia using the wsp assay. We identified four strains of Wolbachia infecting two B. dorsalis mitochondrial haplotypes. We found no strict association between the infecting strain and host haplotype, with one strain being present in two different host haplotypes. All the detected strains belonged to Super Group B Wolbachia and did not match any strains reported previously in B. dorsalis in Asia. These findings indicate that diverse Wolbachia infections are present in invasive populations of B. dorsalis

Optimizing Western Flower Thrips Management on French Beans by Combined Use of Beneficials and Imidacloprid

Western flower thrips (WFT), Frankliniella occidentalis (Pergande), is an important pest of vegetable crops worldwide and has developed resistance to many insecticides. The predatory mites Neoseiulus (=Amblyseius) cucumeris (Oudemans), the entomopathogenic fungus Metarhizium anisopliae (Metsch.), and an insecticide (imidacloprid) were tested for their efficacy to reduce WFT population density and damage to French bean (Phaseolus vulgaris L.) pods under field conditions in two planting periods. Metarhizium anisopliae was applied as a foliar spray weekly at a rate of one litre spray volume per plot while imidacloprid was applied as a soil drench every two weeks at a rate of two litres of a mixture of water and imidacloprid per m(2). Neoseiulus cucumeris was released every two weeks on plant foliage at a rate of three mites per plant. Single and combined treatment applications reduced WFT population density by at least three times and WFT damage to French bean pods by at least 1.7 times compared with untreated plots. The benefit-cost ratios in management of WFT were profitable with highest returns realized on imidacloprid treated plots. The results indicate that M. anisopliae, N. cucumeris, and imidacloprid have the potential for use in developing an integrated pest management program against WFT on French beans.BMZ/GIZ/07.7860.5-001.0

Modeling the risk of invasion and spread of Tuta absoluta in Africa

Tuta absoluta is an invasive insect that originated from South America and has spread to Europe Africa and Asia. Since its detection in Spain in 2006, the pest is continuing to expand its geographical range, including the recent detection in several Sub-Saharan African countries. The present study proposed a model based on cellular automata to predict year-to-year the risk of the invasion and spread of T. absoluta across Africa. Using, land vegetation cover, temperature, relative humidity and yield of tomato production as key driving factors, we were able to mimic the spreading behavior of the pest, and to understand the role that each of these factors play in the process of propagation of invasion. Simulations by inferring the pest’s natural ability to fly long distance revealed that T. absoluta could reach South of Africa ten years after being detected in Spain (Europe). Findings also reveal that relative humidity and the presence of T. absoluta host plants are important factors for improving the accuracy of the prediction. The study aims to inform stakeholders in plant health, plant quarantine, and pest management on the risks that T. absoluta may cause at local, regional and event global scales. It is suggested that adequate measures should be put in place to stop, control and contain the process used by this pest to expand its range

Integrated Management of Aphis craccivora in Cowpea Using Intercropping and Entomopathogenic Fungi under Field Conditions

Cowpea aphid, Aphis craccivora, is a major cowpea pest. Cowpea–cereal intercrop alone does not effectively manage the pest. Use of pesticides in intercrop leads to health and environmental risks. Fungal-based biopesticides offer a better option because they are environment- and consumer-friendly. This study assessed the combined effect of Metarhizium anisopliae ICIPE 62 and cowpea–maize intercrop against A. craccivora under six treatments: (1) untreated cowpea monocrop, (2) untreated cowpea–maize intercrop, (3) cowpea monocrop + ICIPE 62, (4) cowpea–maize intercrop + ICIPE 62, (5) cowpea monocrop + Duduthrin insecticide, and (6) cowpea–maize intercrop + Duduthrin during three seasons (long rainy/cold and dry/short rainy). In the cold and dry season, cowpea–maize intercrop treated with ICIPE 62 recorded the lowest infestation/cowpea damage, whereas the leaf yield was comparable to cowpea monocrop treated with ICIPE 62. In the short rainy season, the cowpea–maize intercrop treated with ICIPE 62 recorded the lowest infestation/damage, whereas leaf yield was similar to cowpea–maize intercrop treated with ICIPE 62 in the cold and dry season. Duduthrin in monocrop and intercrop did not reduce aphid infestation/cowpea damage levels in all the seasons. Although the efficacy of M. anisopliae ICIPE 62-based biopesticide could be affected by seasons, it successfully controlled aphid population in cowpea–maize intercrop under field conditions without affecting aphid-associated natural enemies.Peer Reviewe

Screening for attractants compatible with entomopathogenic fungus Metarhizium anisopliae for use in thrips management

Several thrips attractants were screened for compatibility with Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae) and a subset of these for attraction to Megalurothrips sjostedti Trybom  (Thysanoptera: Thripidae). Conidial germination and germ tube length of M. anisopliae were used as  indicators of its compatibility with thrips attractant. Conidial germination and germ tube length differed significantly according to volatiles of different attractants. The highest conidial germination (76.5±3.5%) and longest germ tube length (130.3±13.4 μm) were recorded in the control, followed by methyl anthranilate (63.8±3.8%; 103.8±8.4 μm), cis-jasmone (61.8±5.9%; 93.8±14.4 μm) and  transcaryophyllene (57.7±6.5%; 96.3±15.5 μm) which were found compatible with M. anisopliae. A  Pearson correlation test indicated a significant positive correlation between conidial germination and germ tube length (r =0.6; P<0.0001). The attraction of M. sjostedti to selected thrips attractant also varied significantly among the attractants. Under field conditions, methyl anthranilate was equally attractive to M. sjostedi as Lurem-TR and could be recommended as a thrips attractant that can be combined with M. anisopliae in autoinoculation devices for potential control of M. sjostedti.Key words: Semiochemicals, conidial germination, germ tube length, Megalurothrips sjostedti, attraction,persistence, field

Identification of edible short- and long-horned grasshoppers and their host plants in East Africa

This study adopted morphological and molecular analysis to identify edible grasshoppers and their associated food host plants in Kenya and Uganda. Host plants were identified through molecular analysis of the gut contents of the grasshoppers. Grasshoppers are among the most popular edible insects in East Africa. As an alternative protein, they contribute to improved nutrition and food security, livelihoods, and employment. The study provides a detailed breakdown of morphometric data and species identification factors along with sequencing, identification and phylogenetic analysis of plant and insect DNA.Federal Ministry for Economic Cooperation and Development (BMZ)Netherlands Organization for Scientific ResearchWOTRO Science for Global Development (NWO-WOTRO)Bioresources Innovations Network for Eastern Africa Development (BioInnovate Africa)Rockefeller FoundationAustralian Centre for International Agricultural Research (ACIAR

Endophytic fungi protect tomato and nightshade plants against Tuta absoluta (Lepidoptera : Gelechiidae) through a hidden friendship and cryptic battle

Endophytic fungi live within plant tissues without causing any harm to the host, promote its growth, and induce systemic resistance against pests and diseases. To mitigate the challenging concealed feeding behavior of immature stages of Tuta absoluta in both tomato (Solanum lycopersicum) and nightshade (Solanum scabrum) host plants, 15 fungal isolates were assessed for their endophytic and insecticidal properties. Twelve isolates were endophytic to both host plants with varied colonization rates. Host plants endophytically-colonized by Trichoderma asperellum M2RT4, Beauveria bassiana ICIPE 706 and Hypocrea lixii F3ST1 outperformed all the other isolates in reducing significantly the number of eggs laid, mines developed, pupae formed and adults emerged. Furthermore, the survival of exposed adults and F1 progeny was significantly reduced by Trichoderma sp. F2L41 and B. bassiana isolates ICIPE 35(4) and ICIPE 35(15) compared to other isolates. The results indicate that T. asperellum M2RT4, B. bassiana ICIPE 706 and H. lixii F3ST1 have high potential to be developed as endophyticfungal- based biopesticide for the management of T. absoluta.The icipe core funding provided by UK’s Foreign, Commonwealth and Development Office (FCDO); Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya.http://www.nature.com/srepam2021Forestry and Agricultural Biotechnology Institute (FABI)Zoology and Entomolog