In small plot trials, performed by several institutes in the past years, potassium bicarbonate
proved to be a promising alternative to the use of copper for the control of apple scab in
organic orchards. Feasibility, effectiveness, consequences, and side effects of the
replacement of copper by bicarbonate under practical conditions are largely unknown. In
2007 Five Dutch organic apple growers compared a bicarbonate based scab management
strategy with their standard spray program. The use of 5 kg potassium bicarbonate + 2 kg.
wettable sulphur shortly before rain or during infection development, was the core of the
strategy. It was concluded that the control of apple scab with the potassium bicarbonate
strategy was as effective as the standard spray plan, provided lime sulphur was available
tot cover extreme situations. The applications did not lead to any phytotoxic damage on
leafs or fruits. Potassium bicarbonate tank mixed with a Mn leaf fertilizer however resulted
in severe leaf drop, and necrotic spots on the remaining leafs.
The use of potassium bicarbonate did not increase the potassium content of the fruits
