Soil moisture, relative humidity, and bentazon affect imazethapyr absorption and translocation in common ragweed (Ambrosia artemisiifolia)

Soil moisture, relative humidity (RH), and the addition of bentazon were ex amined for effects on absorption and translocation of C-14-imazethapyr in c ommon ragweed, When common ragweed was growing under conditions of low soil moisture (-300 kPa), absorption of C-14-imazethapyr was reduced from 51 to 42%. Translocation of 14C-imazethapyr was not affected by soil moisture. I n the absence of bentazon, absorption and translocation of C-14-imazethapyr was similar at 65 and 85% RH 48 and 168 h after treatment. Bentazon decrea sed absorption of C-14-imazethapyr from 61 to 26% at 65% RH and from 65 to 57% at 85% RH 168 h after treatment. Bentazon decreased translocation of C- 14-imazethapyr from 35 to 9% at 65% RH and from 30 to 21% at 85% RH when av eraged over time. This reduction in the absorption and translocation of C-1 4-imazethapyr when bentazon was added may result in a reduction in common r agweed control compared to imazethapyr alone when RH is 65% or lower.