Abstract
Globally, vegetable production including tomato is constrained by pests and diseases. The tomato leafminer, Tuta absoluta (Meyrick.), is a major pest of tomato, mainly managed using chemical pesticides. There is a need for integrated pest management (IPM), approaches that are human and environmentally friendly. The study aimed at molecular identification and virulence evaluation of four entomopathogenic nematodes (EPNs) against T. absoluta larvae. The DNA was extracted, sequenced, and phylogeny analyzed. The EPNs virulence was evaluated using the insect baiting technique at different nematode concentrations (0-Control, 100, 150, 200, and 250 infective juveniles/ml of distilled water). Larval mortality data were collected for five days. Molecular identification resulted in nucleotide sequence lengths of 877-895 base pairs (bp). All the isolates were found to be Steinernema species of EPNs. The % similarity of the isolates and their close relatives ranged between 82-100%. The isolates closely matched Steinernema spp. AY230184 (Sri Lanka); AY230186 (Kenya), JN651414 (Ethiopia), and MW151701 (Kenya). The sequences were deposited to Genbank as Steinernema sp. Isolate Kalro 75 (MW150871), Steinernema sp. Isolate Kalro S86 (MW150872), Steinernema sp. isolate Kalro97 (MW150873) and Steinernema sp. Isolate KalroR52 (MW150874). All the EPN isolates were virulent against T. absoluta. Isolate Kalro R52 and Kalro S86 recorded the highest mortality of 76±7.5%; 72±15.0% respectively in the 48 h. There was a significant difference (P < 0.001), between all the isolates and the Control. The four EPNs were virulent and have bio-control potential against, T. absoluta. Research on their virulence against T. absoluta in the field is recommended.
Highlights
The use of chemical pesticides in agriculture has increased over the past decade globally
Among major tomato pests is the tomato leafminer Tuta absoluta Meyrick, which is mainly managed using chemical pesticides that are harmful to humans and the environment (Terzidis et al, 2014; Ochilo et al, 2019)
The molecular analysis of ITS rDNA indicated that the four study isolates were Steinernema species of entomopathogenic nematodes (EPNs)
Summary
The use of chemical pesticides in agriculture has increased over the past decade globally. Among major tomato pests is the tomato leafminer Tuta absoluta Meyrick, which is mainly managed using chemical pesticides that are harmful to humans and the environment (Terzidis et al, 2014; Ochilo et al, 2019). Food, health, and environmental safety concerns have led to a shift to integrated pest management (IPM) strategies. Such strategies are the deployment of biological pest control agents, including entomopathogenic nematodes (EPNs) (Sanda & Sunusi, 2016; Belien, 2018; Singh et al, 2017; Perez-Alvarez et al, 2019; Surendra, 2019)
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