Evaluation of herbicide combinations for livid amaranth (Amaranthus blitum) control in tuberous begonia (Begonia x tuberhybrida)

In the past years livid amaranth (Amaranthus blitum) is observed increasingly in begonia production fields. Control of weeds in begonia is generally done by a combined application of the soil herbicides isoxaben + simazin followed 10 days later by application of the contact herbicide bentazone. This treatment usually controls the weed population sufficiently with exception of amaranth. In 2003 a field trial was conducted to evaluate control of livid amaranth in tuberous begonia with isoxaben, simazin. S-metolachloor, phenmedipham + desmedipham and bentazone. These herbicides were used as combinations of soil treatment and contact herbicides. The results suggest that a soil treatment of isoxaben + S-metolachloor significantly reduces livid amaranth compared to isoxaben + simazin, without a pronounced negative effect on tuber yield. Application of phenmedipham + desmedipham however did not improve control of livid amaranth compared to bentazone.