Abstract
The box tree moth (BTM), Cydalima perspectalis and the fall webworm (FWW), Hyphantria cunea are two invasive pests of forest trees that have been recorded from Hyracinan forests in north Iran for the first time in 2016 and 2002, respectively. In a search for tentative native entomopathogenic nematode species (EPNs) with potential biocontrol ability against lepidopteran pests of forest trees in north Iran, Oscheius myriophilus was isolated by soil-baiting method from forests of Amlash in the east of Gilan province. The Iranian isolate of this species is characterized by 870–1,247 μm long hermaphrodites having 17–20 μm long stoma, vulva at 45.5–53.1% of body length, tail 90–126 μm long, common males with 38–49 μm long spicules and 583–791 μm long dauer larvae. Compared to the type and other populations, no remarkable differences were observed for this population. The phylogenetic affinities of this isolate with other rhabditid nematodes were studied using partial sequences of small, and the D2-D3 expansion segments of the large subunit ribosomal DNA (SSU and D2-D3 LSU rDNA). This is the first record of the species from Iran. The pathogenicity of Iranian isolate of O. myriophilus was evaluated on the larvae of two important aforementioned forest trees pests, BTM and FWW under laboratory conditions. The results indicated that the suspension of 500 infective juveniles per ml (IJs/ml) of the nematode was the most effective treatment on fifth instar larvae of BTM and FWW, causing 100 and 95% mortality after 48 h, respectively. The lethal concentration 50 (LC50) values of the nematode were 74.5, 152.7, 99.9, and 197.3 IJs/ml on fifth and fourth instar larvae of BTM, and fifth and fourth instar larvae of FWW, respectively, after 48 h at 25°C and 60% relative humidity. Together, present results corroborated the efficacy of the Iranian isolate of Oscheius myriophilus for biocontrolling of BTM and FWW in laboratory conditions.
Highlights
The Hyrcanian (Caspian) forests are natural environ ments in the north Iran that are known as the ecological biodiversity hotspots
Evidences have corroborated the pathogenicity of Oscheius spp. on insects, a behavior of which mainly correlated with the endosymbiont bacteria belonging to two genera Serratia Bizio, 1823 and Enterococcus Thiercelin and Jouhaud, 1903 (e.g. Oscheius rugaoensis (Zhang et al, 2012), O. chongmingensis (Zhang et al, 2008) (Fu and Liu, 2019; Liu et al, 2012), O. myriophilus (Castro-Ortega et al, 2020; Liu et al, 2016), O. microvilli (Zhou et al, 2017), O. safricana (Serepa-Dlamini and Gray, 2018) and O. basothovii (Lephoto and Gray, 2019) (Lephoto et al, 2015)
The objectives of this study were to (i) characterize the Iranian isolate of O. myriophilus recovered from north Iran based upon traditional and molecular criteria, and (ii) assess its biocontrol ability against the larvae of two invasive forest pests, box tree moth (BTM) and fall webworm (FWW), in laboratory condition
Summary
The Hyrcanian (Caspian) forests are natural environ ments in the north Iran that are known as the ecological biodiversity hotspots. O. myriophilus was described as an associate of the garden millipede, Oxidis gracilis (Koch) (Diplopoda: Paradoxosomatidae) in California by Poinar (1986) It was later isolated from millipedes in South Australia by Sudhaus and Schulte (1989), European mole cricket, Gryllotalpa gryllotalpa L. from the Black Sea region of Turkey (Erbaş et al, 2017) and a sugar cane crop soil, in Mexico (Castro-Ortega et al, 2020). The objectives of this study were to (i) characterize the Iranian isolate of O. myriophilus recovered from north Iran based upon traditional and molecular criteria, and (ii) assess its biocontrol ability against the larvae of two invasive forest pests, BTM and FWW, in laboratory condition
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