Abstract

Toxicity of chlorantraniliprole was assayed against young (first and second instars) and older larvae (third and fourth instars) of cabbage Pieris rapae (Lepidoptera: Pieridae) on cabbage (Brassicae oleracea), and persistence of field–aged leaf residue of chlorantraniliprole was assayed with 5-old-day larvae of P. rapae on cabbage. Efficacies of chlorantraniliprole and other newer insecticides to P. rapae were tested under field conditions for two seasons in Hubei province in China. The LC₅₀ value of chlorantraniliprole for early and later P. rapae larvae were 7.92 and 11.34 mg/L by contact toxicity, respectively. The LC₅₀ value of chlorantraniliprole for early and later P. rapae larvae were 0.95 and 4.32 mg/L through ingestion, respectively. The toxicity of field-aged leaf residues of chlorantraniliprole (0-, 3-, 5-, 7-, 10-, 14-, 21-, 25-, and 28-day-old residues) declined gradually under the field conditions. Almost all larvae died on day 5 after feeding on the leaves with 0-21-day residue, and the mortalities were as high as 83.3% and 72.5% for the 21- and 25-day-old leaf residues. Chlorantraniliprole application suppressed P. rapae larvae below the economic threshold for 21-28 days. The field efficacy trials show that chlorantraniliprole at 52 mg a.i /L rate was effective against P. rapae larvae on cabbage, providing marketable cabbage with three applications per season. In addition, chlorantraniliprole was as effective as indoxacarb and spinosad and significantly more effective than emamectin benzoate.

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