Efficacy of entomopathogenic nematodes against Phthorimaea (syn. Tuta) absoluta (Lepidoptera: Gelechiidae) in laboratory bioassays and tomato under greenhouse conditions

Abstract Phthorimaea ( Tuta ) absoluta (Meyrick) (Lepidoptera: Gelechiidae), commonly known as the South American leafminer, was first detected in South Africa in 2016. Its resistance to various insecticides in multiple countries underscores the urgent need for integrated pest management (IPM) strategies. Entomopathogenic nematodes (EPNs), traditionally used against soil-dwelling pests, are receiving increasing attention for foliar applications, due to rising insecticide resistance, regulatory restrictions on chemical use and the growing availability of EPN-based products on the market. This study assessed the efficacy of four indigenous EPN species, viz., Steinernema jeffreyense , S. yirgalemense, Heterorhabditis baujardi, and H. noenieputensis against mined final instar larvae and pupae of P. absoluta in laboratory bioassays and on tomato seedlings in a greenhouse experiment. In laboratory bioassays, all EPN species achieved approximately 100% larval mortality, while pupal mortality remained below 42%. In the greenhouse trails, tomato seedlings infested with P. absoluta final instar larvae were treated with EPNs at concentrations of 250, 500, 1,000, and 2000 infective juveniles (IJs) mL −1 . Phthorimaea absoluta larvae were collected 24 h post-treatment and monitored for mortality at 72 h under controlled conditions. Despite low nematode penetration rates in the greenhouse trials, both S. jeffreyense and S. yirgalemense achieved over 80% larval mortality at 1000 and 2000 IJs mL −1 . These findings highlight the potential of EPNs, particularly S. jeffreyense and S. yirgalemense , as promising components of IPM programs targeting P. absoluta in greenhouse-grown tomato production in South Africa.