New entomopathogenic nematodes from semi-natural and small-holder farming habitats of Rwanda

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White grubs are largely unsolved problems in vegetable and tuber production in East Africa. Novel Rwandan as well as international entomopathogenic nematodes (EPNs) were screened in nine laboratory bioassays and two small-scale field trials in 2014 and 2015. Soil-based laboratory bioassays revealed that all EPNs were able to infect Anomala graueri larvae (Coleoptera: Scarabeidae), although a relatively high number of infective juveniles were needed. Rwandan EPNs were as infectious as their corresponding international strains. At 100 infective juveniles per larva, the Heterorhabditis bacteriophora strains (Rwanda14-N-C4a and international H06) as well as the international Steinernema carpocapsae All caused 18 to 22% grub mortality within 7 days compared to the control. At 1000 infective juveniles, both H. bacteriophora strains as well as the Rwandan S. carpocapsae RW14-G-R3a-2 killed 34 up to 58%. The Rwandan Steinernema RW14-M-C2a-3 least performed in the bioassays (2 to 6%). In two Irish potato fields, the into-soil-applied 1 × 10 9 infective juvenile Steinernema RW14-M-C2b-1 per hectare reduced 29 ± 33% and 96 ± 3% of grubs within 30 and 60 days, respectively. About 1 up to 2.5 × 10 9 infective juvenile Steinernema longicaudum X7 per hectare reduced 77 up to 85% of grubs until day 30, respectively, and 82 up to 95% until day 60. Avermectin + Chlorpyrifos tuber coatings reduced 39% of grubs, and Fipronil + Chlorpyrifos reduced 27%, whereas handpicking did not help much. In conclusion, at least Steinernema RW14-M-C2b-1 and S. longicaudum X7 are promising for managing white grubs in tuber production, this is at a rate of at least 1.5 × 10 9 EPNs per hectare, but H. bacteriophora RW14-N-C4a needs further field research. Findings will support the biocontrol product development in Rwanda, including registration if any would be needed for native macrobial biocontrol agents.

Section: Assessment Of Epn Persistencementioning

confidence: 99%

Management of white grubs (Coleoptera: Scarabeidae) with entomopathogenic nematodes in Rwanda

Kajuga

Hategekimana

Yan³

et al. 2018

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“…This underlines the necessity of EPNs screening Sharma et al (2011) and Biondi et al (2018) in a view to boost their efficacy of EPNs. The highest efficacy of local EPN isolates than the exotics could be explained by the fact that these EPNs were isolated in Rwanda (Yan et al 2016), and they might be more adapted to the local conditions than the exotics, which were isolated in a completely different environment. These results agree with the earlier findings where locally isolated biological control agents, including EPNs, performed better than exotics (Lima et al 2017).…”

Section: Resultsmentioning

confidence: 99%

“…RW14-M-C2a-3, Steinernema sp. RW14-M-C2b-1, S. carpocapsae RW14-G-R3a-2, and Heterorhabditis bacteriophora RW14-N-C4a, which were isolated from semi-natural and small-holder farming habitats of Rwanda in the year 2014 (Yan et al 2016). The two exotic EPN species, S. carpocapsae All and H. bacteriophora H06, were obtained from Lvbenyan Biotech Ltd., Guangdong Institute of Applied Biological Resources (GIABR) in China (Kajuga et al 2018).…”

Section: Source and Mass Production Of Epnsmentioning

confidence: 99%

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Potential of entomopathogenic nematode isolates from Rwanda to control the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Ndereyimana

Nyalala

Murerwa

et al. 2019

Tomato leaf miner, Tuta absoluta (Meyrick), is a major threat to tomato production as it can cause up to 100% yield loss under both greenhouse and open-field conditions. Chemical control, which is associated with several undesirable effects, remains the only option readily available for this pest since its invasion of Rwanda in the year 2015. This study assessed the potential of using local isolates of entomopathogenic nematodes (EPNs) in management of T. absoluta in Rwanda. Six EPNs including four locally isolated strains: Steinernema sp. RW14-M-C2a-3, Steinernema sp. RW14-M-C2b-1, S. carpocapsae RW14-G-R3a-2 and Heterorhabditis bacteriophora RW14-N-C4a, and two exotic species: S. carpocapsae All and H. bacteriophora H06 were evaluated. Three bioassays were conducted in the laboratory, using a tomato leaflet with third instar T. absoluta larva in gallery and 9-cm Petri dishes as bioassay arenas in a completely randomized design with three replications. The EPNs were applied at a volume of 1 ml containing 500 infective juveniles per leaflet, while sterile tap water was used as negative control. Larval mortality was checked continuously for 96 h at 24 h interval. The results revealed that all the tested EPNs were able to find and kill T. absoluta larvae inside the leaf galleries; and their efficacy increased with exposure time. The pathogenicity effects were significantly different (p < 0.05) among EPNs. In the first 24 h after inoculation, the efficacy of local EPN isolates (53.3-96.7%) was significantly higher than the one of exotic species (0.0-26.7%). The efficacy of three Rwandan EPN isolates, Steinernema sp. RW14-M-C2a-3, Steinernema sp. RW14-M-C2b-1, and S. carpocapsae RW14-G-R3a-2 was not significantly different from 24 to 96 h after inoculation, except for S. carpocapsae RW14-G-R3a-2 during 24 h after inoculation in bioassay 3. There was insignificant difference among all the EPN isolates after 96 h of exposure. This is the first study carried out in Rwanda that investigated the potential of locally isolated EPNs against T. absoluta. Field experiments should be conducted to fully explore the possibilities of using local EPN isolates in integrated pest management of T. absoluta in Rwanda.

“…Surveys for isolation of EPNs in Africa include Egypt, Kenya, Ethiopia, Tanzania, Benin, Morocco, South Africa, Rwanda, Algeria, Cameroon, and Nigeria. The species of steinernematids and heterorhabditids described in the past 2 decades are H. bacteriophora, S. arenarium, S. glaseri, S. karii, S. yirgalemense, S. weiserii, H. taysearae, and H. indica (Waturu et al, 1997;Waturu, 1998;Mwaniki et al, 2008;Stack et al, 2000) from Kenya; S. yirgalemense, S. ethiopiense, and H. bacteriophora (Nguyen et al, 2004b;Mekete et al, 2005;Tamirou et al, 2012) from Ethiopia; S. cameroonense, S. nyetense, H. baujardi, and H. amazoniensis from Cameroon (Kanga et al, 2012); S. khoisanae, S. citrae, S. sacchari, S. tophus, S. innovationi, S. jeffreyense, S. beitlechemi, S. fabii, S. nguyeni, S. biddulphi, S. litchii, S. yirgalemense, H. bacteriophora, H. safricana, and H. noenieputensis (Nguyen et al, 2006a, b;Malan et al, 2011;Nthenga et al, 2014;Çimen et al, 2014;Çimen et al, 2015;Malan et al, 2015;Çimen et al, 2016;Hatting et al, 2009;Abate et al, 2016;Malan et al, 2016;Steyn et al, 2017;Malan et al, 2008;Malan et al, 2014) from South Africa; S. feltiae and H. bacteriophora (Tarasco et al, 2009;Zamoum et al, 2011) from Algeria; Steinernema sp, H. sonorensis, and H. indica (Zadji et al, 2013;Houssou et al, 2014) from Benin; S. feltiae from Morocco (Akalach and Wright, 1995) and Nigeria (Akyazi et al, 2012); S. carpocapsae and H. bacteriophora from Rwanda (Yan et al, 2016) and S. pwaniensis (Puza et al, 2017) from Tanzania.…”

Section: Africamentioning

confidence: 99%

Global distribution of entomopathogenic nematodes, Steinernema and Heterorhabditis

Bhat

Chaubey

Askary

2020

100

Entomopathogenic nematodes (EPNs) in the families' Steinernematidae and Heterorhabditidae are obligate insect parasites. Their easy multiplication, broad host range, compatibility with chemical pesticides, and ease in application has grabbed interest among research practitioners to work on these beneficial microorganisms. Till date, around 100 valid species of Steinernema and 21 species of Heterorhabditis have been identified from different countries of the world. Extensive surveys have been conducted across the globe to isolate locally adapted EPN species and exploit them to suppress soil-dwelling and foliar insect pests in agricultural fields. Most of the new species have been described from Asia, whereas research in some Asian countries are still at infancy. Some new species have been recorded from Australia but very few surveys have been conducted in New Zealand. Likewise, less information about these tiny creatures is from Central America; however, in North America many new species have been described, some of which have been commercialized for insect pest control, whereas in South America, several native nematode species have been described and exploited as biological control agents. European countries have also been explored for EPN diversity and new species have been reported, exploited under field condition, and commercialized. Many new species and other previously described species have been reported from Africa. Despite frequent surveys in different continents of the world, number of sites touched are low and, therefore, further surveys are still needed to explore untouched geographic areas and climatic conditions, both in plantations and indigenous forests with an aim to identify and exploit additional EPN species.