Pathogenicity of five entomopathogenic nematodes to Tuta absoluta
Author of the article:GUO Wen-Xiu, WANG Xiao-Yu1, LI Li-Li, Lü Su-Hong, CUI Hong-Ying, SONG Ying-Ying, YU Yi, MEN Xing-Yua
Author's Workplace：Shandong Key Laboratory for Green Prevention and Control of Agricultural Pests, Institute of Plant Protection, Shandong Academy of Agricultural Sciences
Key Words：Tuta absoluta; entomopathogenic nematode; larva; pupa; pathogenicity; biological control
Abstract：
Abstract [Aim] To examine the effect of infection of the 2nd and 4th instar larvae and pupae of Tuta absoluta by entomopathogenic nematodes (EPNs). [Methods] The pathogenicity of five EPNs, Steinernema carpocapsae All, S. longicaudum X-7, S. feltiae SN, Heterorhabditis bacteriophora H06 and H. indica LN2, to 2nd and 4th instar mature larvae and pupae were determined using bioassays. [Results] In a petri dish bioassay, infection with the five EPNs (10 IJs/insect) resulted in ≥ 88.33% and 100.00% corrected mortalities of the 2nd and 4th instar larvae after 72 h. Infection with Steinernema spp. was relatively virulent to pupae compared to Heterorhabditis spp. Significantly higher corrected mortalities of pupae (81.25% and 70.73%) were caused by S. carpocapsae All and S. longicaudum X-7 at a dosage of 10 IJs/insect compared to the same dosage of H. bacteriophora H06 (62.50%) and H. indica LN2 (52.08%) (F = 6.702; df = 4, 20; P < 0.001). Under simulated conditions, 100% corrected mortality of the 2nd instar larvae on leaves were caused by infection with the five EPNs at a dosage of 15 IJs/cm2 after 72 h. Infection with the five EPNs at a dosage of 15IJs/cm2 also resulted in 100% corrected mortality of 4th instar larvae in soil were after 72 h. Infection with S. carpocapsae All at a dosage of 20 IJs/cm2 caused significantly higher corrected mortalities (79.17%) of pupae in soil than infection by S. longicaudum X-7 (64.58%) and S. feltiae SN (62.50%) (F = 10.176; df = 2,12; P = 0.003). [Conclusion] Steinernema carpocapsae All, S. longicaudum X-7, S. feltiae SN, H. bacteriophora H06, H. indica LN2 are highly virulent to T. absoluta larvae on leaves, which could be used to evaluate their efficacy as biological controls for this pest in the field. Leaf surface protectants can be developed to stabilize or enhance the efficacy of EPNs applied to leaves. Infection with S. carpocapsae All resulted in higher corrected mortalities of 4th instar larvae and pupae in soil than infection by S. longicaudum X-7 and S. feltiae SN, which suggests that S. carpocapsae All has the potential to control T. absoluta in soil.