ABSTRACT
Plant diseases caused by insect pests and pathogens account for an estimated 23.1% of maize production loss annually, which translate to between 14.2 and 21 million metric tonnes (Oreke et al., 1995; Oreke, 2006). Emerging plant diseases (EPDs) are a significant constraint to agricultural productivity and profitability. They act as barriers to economic development, threaten ecosystems due to their impact on native biodiversity and control measures incur additional costs leading to indirect loses (Anderson et al., 2004; Fisher et al., 2012; Vurro et al., 2010). Disease outbreaks can spread rapidly and often result in enormous crop losses that can lead to considerable human suffering. For instance, this has been observed following the outbreak of maize lethal necrosis (MLN) in Kenya in 2011 (Fig. 1) (Wangai et al., 2012; Mahuku et al., 2015a). The best strategy to avoid losses is to stop disease from spreading at an early stage, or to prevent outbreaks altogether. This
relies on rapid and accurate identification of the causal agent(s) and the deployment of appropriate control measures. This is particularly critical in outbreaks of new diseases or of those hitherto unknown in a region or on a crop. Such a situation often demands that new control measures must be found as quickly as possible to prevent the disease from spreading.
