Field tests showed that the lawn spray-gun with a 4 gpm lawn tip reduced the percentage of application volume deposited 90 cm to 210 cm downwind from the spray swath edge when compared with XR8004 flat-fan or RA-6 wide angle hollow cone applications at wind speeds between 4.7 and 14.4 km/h. The percentage of applied volume collected at 210 cm downwind from the XR8004 flat-fan applications was 5 and 16 times greater than the percentage from the RA-6 Raindrop nozzle and lawn spray-gun applications, respectively. Visible injury alone with height increases and fresh weights from tomato plants located downwind from the applications concur with spray-drift data for all nozzle types. Triclopyr injury decreased as the distance from the swath edge increased. All tomato plants located downwind up to 210 cm from the XR8004 flat-fan applications were visibly injured (15 to 40%); whereas, only plants less than 150 cm downwind from the RA-6 Raindrop applications and less than 90 cm downwind from the lawn spray-gun applications were injured (2 to 8%).

Water use by weeds is one type of loss that contributes to the cost of weeds to agriculture. Water use efficiency provides a mechanism by which water use by weeds can be estimated. Uncontrolled weed growth could result in estimated irrigation costs exceeding $50.00/ha. Weeds like barnyardgrass at threshold densities in irrigated crops like sugarbeet or tomato are estimated to increase production costs by about $20.00/ha depending on water cost.

Experiments were conducted to determine the interaction between cupric hydroxide and paraquat on the control of American black nightshade. Three cupric hydroxide applications lowered paraquat toxicity with no further decrease in toxicity with six or nine cupric hydroxide applications when paraquat was applied 3 days after the last cupric hydroxide application. The interval between the last cupric hydroxide application and paraquat application was more important in decreasing paraquat toxicity than the number of cupric hydroxide applications. Three cupric hydroxide applications with a 10-day interval before paraquat application decreased paraquat toxicity less than three cupric hydroxide applications with a 3-day interval before paraquat application. Plants collected from three American black nightshade populations (Naples, Bradenton, and Gainesville) differed in their sensitivity to paraquat. I50 values, based on dry weight, showed Naples plants to be 12 times more tolerant to paraquat than Gainesville plants without cupric hydroxide, and 14 times more tolerant when cupric hydroxide was applied. More plants of the Naples biotype regrew from apical buds after paraquat treatment following cupric hydroxide application, and from axillary buds with paraquat but not cupric hydroxide treatment, than did the Bradenton biotype. Plants of the Gainesville biotype did not regrow after paraquat application, regardless of cupric hydroxide treatment.