Efficacy of rice insecticide seed treatments at selected nitrogen rates

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 levels in particular, may contribute to this variability in performance. We conducted two trials at the Pine Tree Experiment Station in St. Francis County to examine the response of rice plants when exposed to different insecticide seed treatments and nitrogen rate combinations. Nitrogen was applied at 0, 45, 90, 135, and 180 pounds per acre to rice plots. Insecticide seed treatments included clothianidin (NipsIt Inside®),thiamethoxam (CruiserMaxx™), and a non-treated control. Plant stand counts and plant heights were taken to evaluate plant vigor, and leaf scar counts and soil core samples were taken to evaluate control of rice water weevil (Lissorhoptrus oryzophilus Kuschel). NipsIt Inside averaged 3.71 larvae per core, CruiserMaxx averaged 4.80, and the non-treated control averaged 10.82. 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. Overall, the non-treated control averaged one more scar than either insecticide seed treatment, with less scarring observed as nitrogen rates increased. Plant samples were taken at mid-season and early heading to measure nitrogen uptake. No differences in uptake were observed between the insecticide seed treatments or the non-treated control. Preliminary results in these trials indicate that nitrogen has no effect on the efficacy of rice seed treatments.