Insecticide Resistance of the Green Rice Leafhopper, Nephotettix cincticeps, to the Systemic Insecticides Used for Seedling-Box Application

Jirapong Jairin^a,* Nobuki Kojima^b and Toru Nagata^c

ABSTRACT: The mortality and feeding inhibition of the green rice leafhopper (GLH), Nephotettix cincticeps Uhler, to four systemic insecticides, namely imidacloprid, cartap, propaphos and disulfoton, were determined by a parafilm method. The three local populations of GLH with different resistance levels to organophosphates (OPs) were compared with respect to LC₅₀ and FI₅₀ obtained by this testing method. Feeding inhibition at sublethal doses was most remarkable, with imidacloprid followed by cartap with no regard to resistance levels, while feeding inhibition by propaphos and disulfoton was observed only with the OPs resistant GLH. The residual period of imidacloprid granule (2%) and cartap granule (4%) applied to the seedling-box were determined in terms of mortality and feeding inhibition. Imidacloprid gave the longest residual period of lethal action and feeding inhibitory action. The GLH population was remarkably reduced in the imidacloprid treated plot compared to the untreated plot, while a reduction in population density was not observed in the cartap treated plot.

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a Ubon Ratchathani Rice Research Center, P.O. Box 65, Muang, Ubon Ratchathani 34000,Thailand.
b Tsukuba International Centre, 3-6 Koyadai, Ibaraki 305-0074, Japan.
c Faculty of Agriculture, Ibaraki University, Ami, Ibaraki 300-0393, Japan.

* Corresponding author, E-mail: jirapongj@ricethailand.org

Received 30 Sep 2004, Accepted 13 Dec 2004