Ultrahigh-frequency electromagnetic fields for weed control: phytotoxicity and selectivity.

An ultrahigh-frequency electromagnetic field (2450+/-20 megahertz) is lethal to plants and seeds of several species after relatively short exposure times. Some species are highly susceptible; others are relatively resistant to a given field intensity. Phytotoxicity is increased in imbibed seeds and young plants. It is decreased in dry seeds and sometimes decreased in mature plants. Soil partially attenuates the field but is not opaque to it.