An electrical energy processing unit of apparatus to kill a plant or at least attenuate plant growth, the electrical energy processing unit comprising: a converter configured to receive unprocessed electrical energy from an electrical energy source, to convert the unprocessed electrical energy to processed electrical energy and to output said processed electrical energy to an applicator unit； a control circuit operable to control the converter to convert the unprocessed electrical energy to the processed electrical energy, wherein the processed electrical energy comprises a waveform with a frequency of at least 18 k Hz and with a peak voltage of at least 1 k V.
