SPRAY DEPOSITION OF FENOXAPROP AND IMAZAMETHABENZ ON WILD OAT (AVENA-FATUA) AS INFLUENCED BY ENVIRONMENTAL-FACTORS

The effect of soil moisture, temperature, and light intensity on the s pray deposition of fenoxaprop and imazamethabenz applied to wild oat p lants was examined by using fluorescent tracer dye, Based on either bi omass or total leaf area, the apparent deposition of the two herbicide s diminished in the following order: shading > low temperature greater than or equal to drought greater than or equal to ''optimum'' > high temperature, The enhanced phytotoxicity of both herbicides under shadi ng could be associated with increased spray deposition; and reduced fe noxaprop phytotoxicity under high temperature stress could be related to reduced deposition, Changes in spray deposition were attributed mai nly to differences in herbicide interception due to altered plant morp hology. Reduced retention for both herbicides was exhibited only in th e plants grown at high temperature, Under ''optimum'' conditions, feno xaprop phytotoxicity was directly associated with leaf orientation and thus with the proportion of projected leaf area at the time of herbic ide spraying, Given similar application conditions, spray deposition o f fenoxaprop and imazamethabenz on wild oat could be estimated by dete rmining the ratio of the projected leaf area, as measured by an image analyzer to the total leaf area.