Optimisation of hot-water application technology for the control of broad-leaved dock (Rumex obtusifolius)

In organic farming, the control of broad-leaved dock (Rumex obtusifolius) via hot-water treatment of the upper root region (hypocotyl) is a new alternative to the current standard control method involving manual digging-out of the roots. This comparative study looks at five different hot-water application techniques. The aim is to optimise the control method in terms of water and energy requirement to obtain a mortality rate of the treated plants of at least 80%. The studied parameters were the application, the amount of water, the water temperature, the soil moisture content and the soil type. In total, 813 plants of varying size were treated (120-225 plants per treatment). The success of each treatment was rated 12 weeks after it was applied. Based on the results, the preferred treatment in terms of water and energy requirement was a commercially available rotary nozzle. With this nozzle, for example, at 40 vol.-% soil moisture, 1.6 L of water at a temperature of 90°C was necessary for successful Rumex control. The rotary nozzle could be used as a non-contact system, and was therefore the most user-friendly of the application techniques examined.