Apparatus and method for electrically killing plants

1 . An electrical apparatus to kill a plant or at least attenuate plant growth, the apparatus comprising:

an electrical energy supply unit;

an applicator unit comprising an applicator electrode;

a return unit comprising a return electrode;

electrical circuitry;

the electrical energy supply unit comprising one or more capacitors which are arranged distal from the applicator electrode and the return electrode, the electrical energy supply unit arranged to apply electrical energy through a transmission circuit comprising the applicator electrode, and the return electrode,

wherein the electrical circuitry is arranged to control a frequency of the electrical energy through the electrical energy supply unit by dynamically varying the frequency during treatment of the plant in response to a determined change in an electrical property related to an electrical impedance value of the plant to control a property of the electrical energy to the electrodes, wherein the property is one or more of voltage, current, or power.

2 . The apparatus of claim 1 , wherein said electrical circuitry implements a plant monitoring system to determine the electrical property related to the electrical impedance value of the plant, the electrical circuitry arranged to control said electrical impedance value of the electrical energy supply unit based on said determined electrical property to control said property of the electrical energy to the electrodes.

3 . The apparatus of claim 2 , wherein the plant monitoring system is arranged to determine the electrical property related to the electrical impedance value of the plant by measuring one or more properties of the electrical energy through the transmission circuit.

4 . The apparatus of claim 1 , wherein the electrical energy supply unit and the transmission circuit are arranged with the electrical impedance value of the electrical energy supply unit to control the power and/or the voltage of the electrical energy applied through the transmission circuit between said electrodes.

5 . The apparatus of claim 2 , wherein the electrical circuitry to control the electrical energy supply unit to maintain the electrical impedance value thereof to be within a predetermined amount of the electrical impedance value between the electrodes.

6 . The apparatus of claim 1 , wherein the electrical energy supply unit and the transmission circuit are arranged with a reduction of the electrical impedance value of the electrical energy supply unit to increase the power of the electrical energy applied through the transmission circuit between said electrodes.

7 . The apparatus of claim 1 , wherein the electrical energy supply unit includes an inductive element and the one or more capacitors arranged as a resonant circuit, wherein the electrical circuitry is arranged to change the electrical impedance value of the electrical energy supply unit to control the power by changing one or more of: the frequency of the electrical energy; an inductance of the inductive element; a capacitance of the one or more capacitors.

8 . The apparatus of claim 7 , wherein the electrical circuitry arranged to operate the resonant circuit offset from resonance by at least ±5%.

9 . The apparatus of claim 2 , wherein the electrical circuitry arranged to transition the electrical impedance value of the electrical energy supply unit to a lower value, when the determined electrical property indicates the electrical impedance value of the plant is below a transition threshold.

10 . The apparatus of claim 9 , wherein the electrical circuitry arranged to control the electrical energy to be applied as a first stage and a second stage,

wherein during the first stage an electrical potential over the electrodes is controlled to be above a first threshold,

wherein during the second stage an electrical potential over the electrodes is controlled to be below the first threshold; and

wherein the electrical circuitry arranged to transition to the second stage when the determined electrical property indicates the electrical impedance value of the plant is below the transition threshold.

11 . The apparatus of claim 10 , wherein the electrical circuitry arranged to control the power of the electrical energy during the second stage to be greater than in an alternative second stage wherein the electrical impedance value of the electrical energy supply unit was not changed from that of the first stage.

12 . The apparatus of claim 10 , wherein the electrical circuitry arranged to, prior to the first stage, increase said electrical potential to the first threshold over a predetermined period of time.

13 . The apparatus of claim 11 , wherein the electrical circuitry arranged to determine, based on the determined electrical property, that the electrical impedance value is above a treatment completion threshold and to re-execute the first stage.

14 . The apparatus of claim 11 , wherein the electrical circuitry arranged to determine, based on the determined electrical property, the electrical impedance value is below a short circuit threshold and to prevent supply of the electrical energy to the electrodes.

15 . The apparatus of claim 9 , wherein the electrical circuitry arranged to transition the electrical impedance value of the power supply unit sequentially to a plurality of lower values each corresponding to when one of a plurality of sequentially lower transition thresholds is met.

16 . A method of treating a plant with electrical energy, the method comprising:

applying the electrical energy, with an electrical energy supply unit comprising one or more capacitors, which are arranged distal from an applicator electrode and a return electrode, the electrical energy applied to the plant from the applicator electrode and the return electrode;

in response to a determined change in an electrical property related to an electrical impedance value of the plant; and

controlling a frequency of the electrical energy through the electrical energy supply unit by dynamically varying the frequency during treatment of the plant based on a monitored said electrical property to control a property of the electrical energy to the electrodes, wherein the property is one or more of voltage, current, or power.

17 . The method of claim 16 comprising:

determining the electrical property related to the electrical impedance value of the plant between said electrodes;

controlling the electrical impedance value of the electrical energy supply unit based on the determined said electrical property.

18 . An electrical apparatus comprising, electrical circuitry to implement the method of claim 16 .

19 . An electrical apparatus comprising, a computer program to implement the method of claim 16 .