Using Panel Community Surveys to Track the Impact of Crop Pests Over Time and Space – The Case of Maize Lethal Necrosis (MLN) Disease in Kenya from 2013 to 2018

Abstract

Maize lethal necrosis (MLN) disease appeared in Kenya in 2011, causing major damage. In a first survey of 121 communities in 2013, participants estimated the proportion of households affected and the yield loss in affected areas; from this survey, the overall loss was estimated at 22% (0.5 million tonnes per year), concentrated in western Kenya (94%). Efforts to combat the disease included planting resistant varieties, creating awareness of MLN management, and producing pathogen-free seed. In 2018, the same communities were revisited and asked the same questions, establishing a panel community survey. The results showed that incidents of MLN had greatly decreased, and the number of communities that had observed it had reduced from 76% in 2013 to 26% by the long rains of 2018; while still common in western Kenya (60%), MLN had greatly reduced elsewhere (to 10%). In 2013, 40% of farmers were affected, yield loss among affected farmers was estimated at 44%, and total yield loss was estimated at 22% (a production loss of 0.5 million tonnes/year), valued at US$ 187 million. By the long rains of 2018, 23% of farmers were affected, with a loss among affected farmers of 36%; overall annual loss was estimated at 7.5% or 0.37 million tonnes, valued at US$ 109 million, concentrated in western Kenya (82%). Of the recommended control measures, only the removal of diseased plants was commonly used (by 62% of affected communities), but not the use of agronomic practices (11%) or resistant varieties (9.5%). The reasons for the reduction in MLN are not well understood; external factors such as spraying insecticide against fall armyworm and unfavorable weather likely played a role, as did using disease-free seed, but not the use of resistant varieties or appropriate management practices. Still, as the pathogen is still in the fields, it is important to keep disseminating these control methods, in particular resistant varieties.

Translating virome analyses to support biosecurity, on-farm management, and crop breeding

“…MCMV and SCMV can be seed transmitted, at low rates depending on the variety, and both are vectored by insects – Chrysomelid beetles in the case of MCMV and aphid species in the case of SCMV ( Hilker et al., 2017 ; Redinbaugh and Stewart, 2018 ; Regassa et al., 2021 ). Diagnostics can indicate needed management strategies, however, smallholder farmers may not be able to afford inputs such as pesticides, certified clean seed and other management strategies ( De Groote et al., 2020 ). A survey of farmers in Kenya from 2013 to 2018 reported a reduction in MLN by removing infected plants, implementation of resistant varieties and other control measurements ( De Groote et al., 2020 ).…”

“…Diagnostics can indicate needed management strategies, however, smallholder farmers may not be able to afford inputs such as pesticides, certified clean seed and other management strategies ( De Groote et al., 2020 ). A survey of farmers in Kenya from 2013 to 2018 reported a reduction in MLN by removing infected plants, implementation of resistant varieties and other control measurements ( De Groote et al., 2020 ). The International Maize and Wheat Improvement Centre (CIMMYT) implemented rapid development of tolerant and resistant maize in Kenya, which likely helped to control MLN incidence ( De Groote et al., 2020 ).…”

“…A survey of farmers in Kenya from 2013 to 2018 reported a reduction in MLN by removing infected plants, implementation of resistant varieties and other control measurements ( De Groote et al., 2020 ). The International Maize and Wheat Improvement Centre (CIMMYT) implemented rapid development of tolerant and resistant maize in Kenya, which likely helped to control MLN incidence ( De Groote et al., 2020 ). However, despite efforts to train farmers and individuals on managing disease epidemics, there are still challenges to be addressed so that all farmers have access to needed information ( Parsa et al., 2014 ; Buddenhagen et al, 2022 ; Streulens et al., 2022 ).…”

What Can Be Learnt by a Synoptic Review of Plant Disease Epidemics and Outbreaks Published in 2021

“…The avoidance of crop loss due to disease is a major motivation for making improvements in disease management and prediction and for securing global food supplies (Savary et al 2012, Savary et al 2019, Savary and Willoquet, 2020, especially for pathogens of the major staple food crops such as wheat and rice (Ficke et al 2018, Savary et al 2022. Household surveys in Kenya have shown very high losses in maize due to maize lethal necrosis (MLN), approaching 80% in the western highland tropical and moist transitional zones (de Groote et al 2021;Electronic Supporting Information, S5). Fewer quantitative data are available for pathogens of minor or speciality food crops, including pome fruit and grapevine (Trad andTaoueb 2021, Frem et al 2021; Electronic Supporting Information, S5) although, because of higher per unit horticultural value, estimates of economic loss have been made.…”

Discovery and Validation of a Recessively Inherited Major-Effect QTL Conferring Resistance to Maize Lethal Necrosis (MLN) Disease

“…Increasing trade and travel coupled with weak phytosanitary systems are accelerating the global spread of devastating crop pests and diseases (McDonald and Stukenbrock, 2016;De Groote et al, 2021). The maize lethal necrosis (MLN) is one such transboundary maize disease that emerged in eastern Africa in 2011 (Mahuku et al, 2015;Prasanna et al, 2020).…”