6 A Brief History of Microwave Weed Control Research

Abstract

Interest in the effects of high frequency electromagnetic waves on biological materials dates back to the late 19th century (Ark & Parry, 1940), while interest in the effect of high frequency waves on plant material began in the 1920s (Ark & Parry, 1940). Many of the earlier experiments on plant material focused on the effect of radio frequencies (RFs) on seeds (Ark & Parry, 1940). In many cases, short exposure resulted in increased germination and vigour of the emerging seedlings (Nelson, Ballard, Stetson, & Buchwald, 1976; Nelson & Stetson, 1985; Tran, 1979); however, long exposure usually resulted in seed death (Ark & Parry, 1940; Bebawi et al., 2007; Brodie et al., 2009). Davis et al. (1971; 1973) were among the first to study the lethal effect of microwave heating on seeds. They developed a set of prototypes, called “Zappers”, which they tested in the field for their Company and federal and state researchers. Their final prototype, designated Zapper III, underwent tests underwent tests to provide the data necessary for the construction of the first semi-commercial prototype. In October 1971, the Company purchased all proprietary rights to a discovery made at Texas A&M University concerning the toxic effects of microwaves on plants Davis et al. (1971; 1973).