Water Quality and Insecticide Efficacy of Rice Seed Treated With An Insecticide Seed Treatment When Seeded in Soil Amended With Biochar.

Biochar, a carbon-rich material, has been used as a soil amendment to improve productivity, filtration of soil water, and sequestering carbon.  Due to the sorption properties of activated carbons, bioavailability of certain agrochemicals can be reduced. Recently, two new insecticides have received Section 3 labels as seed treatments in rice (i.e., Cruiser [thiomethoxam] and Dermacor [rynaxypyr]).  Both seed treatments are systemic to be effective against target pests. The objectives of this research are to:  1. examine the quality of water drained from soils amended with varying amounts of biochar when planted with rice seed treated with Cruiser and Dermacor, compared with the standard insecticide treatment, a foliar applied pyrethroid, and 2. examine the efficacy of Dermacor against fall armyworm when Dermacor treated seed is planted in soils amended with varying amounts of biochar. Seeds were treated with Dermacor at a rate of 0.08 lb AI/A (2.5 fl oz/100 lbs of seed seeded at 80 lbs/A) or Cruiser 0.03 mg AI/seed and planted into pots with soil amended with 0, 5, 15 and 30% (by weight) biochar.  To quantify  the concentrations of Cruiser and Dermacor in water, we have developed a very sensitive analytical method with limit of detection of 5-10 ng/L (part per trillion) using high performance liquid chromatography coupled with tandem mass spectrometry (LC-MSMS).  The results suggested that the  amendment of biochar did not affect the bioavailability and efficacy of Cruiser and Dermacor.