The diversity of aphid parasitoids inEast Africaand implications for biological control

Abstract

BACKGROUND: Hymenopteran parasitoids provide key natural pest regulation services and are reared commercially as biological control agents. Therefore, understanding parasitoid community composition in natural populations is important to enable better management for optimized natural pest regulation. We carried out a field study to understand the parasitoid community associated with Aphis fabae on East African smallholder farms. Either common bean (Phaseolus vulgaris) or lablab (Lablab purpureus) sentinel plants were infested with Aphis fabae and deployed in 96 fields across Kenya, Tanzania, and Malawi. RESULTS: A total of 463 parasitoids emerged from sentinel plants of which 424 were identified by mitochondrial cytochrome oxidase I (COI) barcoding. Aphidius colemani was abundant in Kenya, Tanzania and Malawi, while Lysiphlebus testaceipes was only present in Malawi. The identity of Aphidius colemani specimens were confirmed by sequencing LWRh and 16S genes and was selected for further genetic and population analyses. A total of 12 Aphidius colemani haplotypes were identified. Of these, nine were from our East African specimens and three from the Barcode of Life Database (BOLD).CONCLUSION: Aphidius colemani and Lysiphlebus testaceipes are potential targets for conservation biological control in tropical smallholder agro-ecosystems. We hypothesize that high genetic diversity in East African populations of Aphidius colemani suggests that this species originated in East Africa and has spread globally due to its use as a biological control agent. These East African populations could have potential for use as strains in commercial biological control or to improve existing Aphidius colemani strains by selective breeding.

Plant-Rich Field Margins Influence Natural Predators of Aphids More Than Intercropping in Common Bean

“…With the sticky trapping, the most abundant taxa were parasitic wasps (Ichneumonidae and Braconidae), with the Braconidae (particularly Aphidius colemani ) being the dominant family) while with the sweep netting the most abundant taxa were the predatory flies (Dolichopodidae and Asilidae) with the Dolichopodidae being the dominant family in the study. The hymenopteran taxonomic data were obtained from a parallel study using mitochondrial cytochrome oxidase I barcoding of insects collected from sentinel plants, showing the common hymenopteran groups present in the study area [ 58 ]. The high-diversity fields had a significantly higher number of lady beetles, predatory flies, hoverflies, predatory bugs, parasitic flies, other predatory beetles ( p = 0.001), and lacewings ( p = 0.005), caught through sticky trapping used to monitor the field margins for NEs, than the fields with low diversity.…”

Sizing the Knowledge Gap in Taxonomy: The Last Dozen Years of Aphidiinae Research

“…On the other hand, the same species was introduced in South Africa (in 1969), where it apparently failed to establish colonies, and also in Kenya, but the fate of the released parasitoids is unknown [80]. Recently, L. testaceipes was recorded in high numbers in both Western (Benin) [97] and Eastern Africa (Malawi) [98]. Although its origin is unknown in both countries, it most likely spread naturally from South Africa or Kenya.…”

“…In the last few years, different researchers started using DNA barcodes for the molecular identification of Aphidiinae [79,98,136]. The identification of Aphidiinae based solely on molecular data (barcodes) is not reliable, because species and genera boundaries, based on barcoding sequences, vary significantly.…”

“…In ecological studies, the use of the fastest DNA extraction protocols is still common practice, even if they are destructive and leave no voucher specimens. The aforementioned studies about the Aphidius colemani group in Eastern Africa [98,136] and the native Aphidiinae of New Zealand [68] used destructive DNA extraction protocols and lost potentially very valuable information, while those from New Zealand probably also lost several as yet undescribed species. There are a number of nondestructive protocols, e.g., [138][139][140] that could and should be used for voucher specimens.…”

Early monitoring of parasitism by Aphidiinae parasitoids on the grain aphidSitobion miscanthiin wheat fields usingDNAbarcoding

“…This method is currently used for insect classification and identification, analysis of species diversity and parasite–host interactions, estimation of parasitism rate, and food web studies in ecosystems 13–17 . DNA barcoding is also used to accurately detect and identify Aphidiidae species, even inside their aphid hosts 18–20 . Sequencing a ~700‐bp fragment of the mitochondrial cytochrome oxidase subunit I ( COI ) gene reliably identifies most insect species 21 .…”