Biological Control of Diamondback Moth, Plutella xylostella with Korean Isolates of Entomopathogenic Nematodes (Steinernematid and Heterorhabditid) in Greenhouse
Five strains of Korean entomopathogenic nematodes (EPN), steinernematids and heter-orhabditids were evaluated and tried in laboratory, pot, and vegetable greenhouses for environmentally friendly control of diamondback moth (DBM), Plutella xylostella, from 2002 to 2005. LC₅₀ values of five EPN strains against DBM were different depending on nematode strain and DBM instar. LC₅₀ value of Steinernema carpocapsae GSN1 (GSN1) was the lowest representing 2.6~3.9 infective juveniles (Ijs, 3rd stage) to 2nd to 4th instars of DBM. Pathogenicity of five effective strains against DBM was different depending on nematode strain, concentration, application times, and vegetable in pot. The most effective nematode was GSN1. Steinernema spp. was more effective than Heterorhabditis spp. against DBM. Two or three times of applications of EPN were effective regardless of nematode strain and concentration in pot. Efficacy of EPN was different depending on vegetable species. Efficacy was higher on Chinese cabbage, red mustard, and Ssamchoo than that on cabbage, kale, and leaf broccoli. Efficacy of GSN1, Steinernema GSNUS-10, Steinernema GSNUS-14, and Heterorhabditis GSNUH-l was variable depending on nematode strain, concentration, application times, and vegetable in greenhouse experiments. GSN1 was the most effective and 100,000 infective juveniles per ㎡ (=1 × 10⁹ Ijs/ha) resulted in higher efficacy. Three times of application of nematodes led to higher control efficacy than one or two applications. Efficacy of nematodes was higher on Chinese cabbage than cabbage or kale in greenhouse.