Estimated annual losses of US$40 billion have been attributed to the effects of biotic stress on crop losses and reduced yields (Rahman et al., 2018). The principal control measure in many agricultural systems has been to spray crops with synthetic pesticides. However, it is estimated that only 0.1% of sprayed chemicals end up contributing to crop protection (Fukamachi, 2019). The remainder is lost to the wider environment, where it poses potential risks to non-target species, human health, and broader agroecosystem function. This has resulted in increasing restrictions on pesticide use. In addition, because of continued exposure to chemical pesticides, predating insects and pathogens have developed resistance to many synthetic pesticides, further limiting use and efficacy (Watson, 2018). Measures such as the development of geneticallymodified (GM) crops have helped control some plant diseases (Bawa and Anilakumar, 2013). However, restrictions on GM crop production in many countries limit its role. This has led to the search for alternative, more sustainable solutions.