Effect of Soil Clay and Organic Matter Content upon Systemic Efficacy of Two Carbamate Insecticides1

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Abstract
Carbamate systemic insecticides were applied to 5 soil mixtures under greenhouse conditions. They were Temik® (2-methyl-2-(methylthio) propionaldehyde O-(methylcar-bamoyl) oxime) and NIA 10242 (2,3-dihydro-2,2-dimethyl-7-.benzofuranyl methylcarbamate). Cotton plants growing in these soils took up the insecticides to varying extents as indicated by aphid bioassay. Of the variability in uptake, 99% was associated with soil clay content. Higher clay soils furnished the toxicant at a lower rate. During the period showing maximum mortality the effect of organic matter content became apparent. The rate at which bioassay mortalities declined increased with soil organic matter content. Temik was taken up more rapidly and persisted longer than NIA 10242. Phytotoxicity was severe in soils low in clay content, whereas, it was virtually nonexistent in those with high clay content. This fact indicated further the greater uptake of toxicant from soils low in clay content. More plant injury occurred with NIA 10242 than with Temik.