Effect of Environment on the Activity of Diphenamid

Abstract

The activity of foliage applications ofN,N-dimethyl-2,2-diphenylacetamide (diphenamid) was greatly enhanced by exposing the plants to high relative humidity for 6 hr immediately after chemical application. Growing plants under low light intensity further increased the activity of diphenamid under these conditions. This response occurred with a number of plant species, including tomato (Lycopersicon esculentum Mill.), Japanese millet (Echinochloa crusgalli(L.) Beauv., var.frumentacea), lettuce (Lactuca sativaL.), and radish (Raphanus sativusL.). Low light, but not high relative humidity, increased the activity of diphenamid as a soil application. Unaltered diphenamid and not its known metabolites seemed to be responsible for the increased activity of foliage sprays under conditions of low light and high relative humidity.