Effect of the application time of clothianidin or fipronil for rice in a seedling growing box on its level in plants

Abstract

If we use the insecticide clothianidin or fipronil in a seedling growing box, we can apply the insecticide just before rice planting (hereinafter, termed as “rice planting treatment”) or after seeding and before the seed is covered by soil (hereinafter, termed as “rice seeding treatment”). With the rice seeding treatment, the clothianidin level in plants at the rice-planting stage was 18.4 mg/kg, which was the highest value, and the level rapidly decreased thereafter. With the rice planting treatment, the clothianidin level increased to 1.53 mg/kg 1 day after rice planting and decreased thereafter. The difference in the levels between both treatments at 28 days from the rice planting was small. The fipronil level with rice seeding treatment was higher than that with the rice planting treatment at the rice-planting stage. But there were little differences in the fipronil levels between both treatments after 1 day from rice planting and thereafter.