Efficacy of rice insecticide seed treatments at selected nitrogen rates for control of Lissorhoptrus oryzophilus kuschel

The value of insecticide seed treatments in rice has been well documented in recent years, but there have been instances where these treatments have not performed as expected.  Soil fertility, nitrogen in particular, is thought to contribute to this variability in performance. Trials were conducted in St. Francis county and Arkansas county to examine the response of rice plants receiving different insecticide seed treatments and nitrogen rate combinations.  Nitrogen was applied at 0, 45, 90, 135, and 180 lb urea-N/acre to rice plots.  Insecticide seed treatments included label rates of clothianidin (NipsIt Inside 5FS), thiamethoxam (CruiserMaxx Rice 5FS), and a non-treated (fungicide only) control.  Both NipsIt Inside and CruiserMaxx had significantly fewer rice water weevil larvae compared to the non-treated control with an equivalent level of nitrogen; however, no differences were found between the two seed treatments at equal nitrogen levels. Nitrogen uptake at panicle differentiation and early heading was not affected by insecticide seed treatments.  As nitrogen rate increased, grain yield increased up to 90 lb urea-N/acre and then plateaued.  Averaged across nitrogen rates, both insecticide seed treatments had similar yields that were greater than the grain yields of the control.  Preliminary results indicate that nitrogen has no effect on the efficacy of rice insecticide seed treatments but does influence the magnitude of leaf scarring and rice water weevil larvae number.