Limited translocation of clothianidin in seed treated maize: Implications for IPM

The neonicotinoids are a relatively new group of insecticides that have come to dominate the seed treatment market of numerous crops.  Neonicotinoid seed treatments aim to provide systemic protection from early season, soil-dwelling secondary insect pests.  Corn is the predominant crop neonicotinoid seed treatments are applied to as clothianidin (Poncho®) or thiamethoxam (Cruiser®).  Given the large-scale use of neonicotinoids in corn and increasing number of neonicotinoid detections in ground and surface waters, a field study was conducted in 2013 and 2014 to determine the amount of seed treatment successfully translocated into a corn plant and by extension, how much persists in the environment.  Corn seed with a treatment rate of 0.25 mg clothianidin per kernel was sampled three times weekly for 47 days post plant (DPP) in 2013.  In 2014, varying rates of seed treatment (control, fungicide only, 0.25 mg, and 1.25 mg of clothianidin per kernel) were sampled three times weekly until 21 DPP with weekly sampling following until 61 DPP.  Five and ten whole plants were collected per sampling event in 2013 and 2014 respectively.  Liquid chromatography mass spectrometry was used to quantify translocated clothianidin.  In 2013, <5% of the initial 0.25 mg application was translocated within the first 9 DPP.  By 12 DPP a maximum of 1.37 and 5.1 µg clothianidin/g plant tissue was reported for the shoot and root regions with both regions decreasing to <0 µg clothianidin/g plant tissue by 19 DPP.  A similar pattern is expected from the 2014 season.