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Characterization of Hymenopteran Parasitoids of Aphis fabae in An African Smallholder Bean Farming System Through Sequencing of COI ‘Mini-barcodes’

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Department of Sustainable Agriculture, Biodiversity and Ecosystems Management, The Nelson Mandela African Institution of Science and Technology, Arusha PO Box 447, Tanzania
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Graham Centre for Agricultural Innovation, Charles Sturt University, PO Box 883, Orange, NSW 2800, Australia
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Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UK
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Royal Botanic Gardens, Kew, Richmond Surrey, TW9 3AB, UK
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Department of Research, Plant Protection Division, Tropical Pesticide Research Institute (TPRI), Arusha PO Box 3024, Tanzania
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Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 35002, China
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Author to whom correspondence should be addressed.
Insects 2019, 10(10), 331; https://doi.org/10.3390/insects10100331
Received: 26 August 2019 / Revised: 8 September 2019 / Accepted: 29 September 2019 / Published: 2 October 2019
Parasitoids are among the most frequently reported natural enemies of insect pests, particularly aphids. The efficacy of parasitoids as biocontrol agents is influenced by biotic and abiotic factors. For example, hyperparasitoids can reduce the abundance of the primary parasitoids as well as modify their behavior. A field study was conducted at three contrasting elevations on Mount Kilimanjaro, Tanzania, to identify the parasitoids of aphids in smallholder bean farming agroecosystems. Sentinel aphids (Aphis fabae) on potted bean plants (Phaseolus vulgaris) were exposed in 15 bean fields at three elevations for 2 days. The sentinel aphids were then kept in cages in a greenhouse until emergence of the parasitoids, which were collected and preserved in 98% ethanol for identification. Of the 214 parasitoids that emerged from sentinel aphids, the greatest abundance (44.86%) were from those placed at intermediate elevations (1000–1500 m a.s.l), compared to 42.52% from the lowest elevations and only 12.62% from the highest elevation farms. Morphological identification of the parasitoids that emerged from parasitized aphids showed that 90% were Aphidius species (Hymenoptera: Braconidae: Aphidiinae). Further characterization by sequencing DNA ‘mini-barcodes’ identified parasitoids with ≥99% sequence similarity to Aphidius colemani, 94–95% sequence similarity to Pachyneuron aphidis and 90% similarity to a Charipinae sp. in the National Center for Biotechnology Information (NCBI) database. These results confidently identified A. colemani as the dominant primary aphid parasitoid of A. fabae in the study area. A Pachyneuron sp., which was most closely related to P. aphidis, and a Charipinae sp. occurred as hyperparasitoids. Thus, interventions to improve landscapes and farming practice should monitor specifically how to augment populations of A. colemani, to ensure any changes enhance the delivery of natural pest regulation. Further studies are needed for continuous monitoring of the hyperparasitism levels and the dynamics of aphids, primary parasitoids, and secondary parasitoids in different cropping seasons and their implications in aphid control. View Full-Text
Keywords: primary parasitoids; hyperparasitoids; Aphidius colemani; Phaseolus vulgaris; natural pest regulation; DNA barcoding primary parasitoids; hyperparasitoids; Aphidius colemani; Phaseolus vulgaris; natural pest regulation; DNA barcoding
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Mkenda, P.A.; Ndakidemi, P.A.; Stevenson, P.C.; Arnold, S.E.J.; Belmain, S.R.; Chidege, M.; Gurr, G.M.; Woolley, V.C. Characterization of Hymenopteran Parasitoids of Aphis fabae in An African Smallholder Bean Farming System Through Sequencing of COI ‘Mini-barcodes’. Insects 2019, 10, 331.

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