Abstract:

Effects of four entomopathogenic nematode strains, i.e., Steinernema carpocapsae All, Steinernema carpocapsae A24, Steinernema feltiae SN, and Heterorhabditis bacteriophora H06, on the oriental fruit fly (OFF), Bactrocera (Bactrocera) dorsalis (Hendel) were investigated both in the laboratory and field. The results showed that among the four tested strains, the strain S. carpocapsae All displayed the strongest pathogenicity. The LD₅₀ and LD₉₅ of S. carpocapsae All in 3 days after treatment against the 3rd instar larvae were 35.0 and 257.1 infective juveniles/cm² soil, respectively. The index of population trend (I) and the interference index of population control (IIPC) based on the life table with affecting factors in different stages in the field populations of B. (B.) dorsalis were used to evaluate the control efficacy of S. carpocapsae All against OFF. The field results showed that when S. carpocapsae All nemotodes in 300 infective juveniles/cm² soil were used to treat the soil, the control efficacy in 9 days after treatment against larvae and pupae reached 86.3%; the I value of OFF was 15.5, significantly lower than 105.9 found in the orchard without nematode treatment; and the IIPC value of OFF in the treated orchard was 0.146, which meant that the population density of OFF in next generation in the treated orchard was reduced to 14.6% of the population density of OFF in the control orchard.
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Key words: Steinernema carpocapsae, Steinernema feltiae, Heterorhabditis bacteriophora, Bactrocera (Bactrocera) dorsalis (Hendel), pathogenicity, control efficacy, life table