Use of electricity to control bolters in sugar beet (Beta vulgaris L.): a comparison of the electrothermal with chemical and mechanical cutting methods

A machine was built to kill reproductive plants (‘bolters’) in sugar beet by high-voltage electricity. A generating system producing 10, 13 or 17 kV each at 54 kW was connected to a set of guarded electrodes spanning twelve rows, suspended 5–15 cm above the top of a sugar-beet crop. With 13 kV the system travelling at 5 km h^?1 could clear a light-to-moderate infestation of bolters at a rate of 2·4 ha h^?1 with the tractor's diesel-fuel consumption at 3·51 ha^?1. In 1979, the electrothermal machine, used twice, reduced viable seed returns by 83%; the flail mower used once or twice by 44 and 76–84%; the wire reel mower used once or twice by 45 and 80–87%; and the roller chemical applicator used once by only 13%. Further trials were made in 1981 with an improved electrothermal machine, a rope wick applicator and a flail mower when all gave over 90% control of viable seeds. The electrothermal machine killed between 38 and 41% of bolters compared with 65% for the chemical applicator. The flail mower did not kill any plants. Although possessing many advantages, the electrothermal machines are heavy and more expensive than alternative methods. Development has ceased in the U.K. on electrical weed control but one company in the U.S.A. is selling such equipment.