Smallholder Cassava Planting Material Movement and Grower Behavior in Zambia: Implications for the Management of Cassava Virus Diseases

Abstract

Cassava is an important food crop across sub-Saharan Africa, where production is severely inhibited by two viral diseases; cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), both propagated by a whitefly vector and via human-mediated movement of infected cassava stems. There is limited information on growers’ behaviour related to movement of planting material, as well as growers’ perception and awareness of cassava diseases, despite the importance of these factors for disease control. This study surveyed a total of 96 cassava subsistence growers and their fields across five provinces in Zambia between 2015 and 2017, to address these knowledge gaps. CMD symptoms were observed in 81.6% of the fields, with an average incidence of 52% across the infected fields. No CBSD symptoms were observed. Most growers used planting materials from their own (94%) or nearby (<10 km) fields of family and friends, although several large transactions over longer distances (10-350 km) occurred with friends (15 transactions), markets (1), middlemen (5), and NGOs (6). Information related to cassava diseases and certified clean (disease-free) seed reached only 48% of growers. The most frequent sources of information related to cassava diseases included nearby friends, family and neighbours, whilst extension workers were the most highly preferred source of information. These data provide a benchmark on which to plan management approaches to controlling CMD and CBSD, which should include clean propagation material, increasing growers' awareness of the diseases and increasing information provided to farmers (specifically disease symptom recognition and disease management options).

How the epidemiology of disease-resistant and disease-tolerant varieties affects grower behaviour

“…Although tolerance and resistance to disease have been widely researched in plant biology, little thought has been given to the distinct epidemiological consequences of deploying tolerant or resistant varieties upon a community of growers, and none to how this affects the decisions of growers to partake in control. Growers’ behaviour more broadly, and its effects on epidemic outcomes remains largely overlooked in plant disease epidemiology (with some exceptions including [30–33,59–61]). Here, we investigated the effect of a fixed proportion of ‘improved’ crop (with either tolerant or resistant characteristics) on growers’ profits and subsequently how this affected growers’ use of improved crop when given the choice.…”

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

“…Such involvement is necessary to improve cooperation and coordination amongst participants (Sherman et al 2019) and should form part of any risk-based approach to disease management (Hyatt-Twynam et al 2017). These concerns were mirrored in studies on Clas in California (Garcia-Figuera et al, 2021), cassava mosaic virus disease in Zambia (Szyniszewska et al 2021) (Electronic Supporting Information, S5). Other studies on disease management of Clas have given detailed accounts of control techniques such as precision trunk inoculation but have not considered the implications for all participants (Li and Nangong, 2021: Electronic Supporting Information, S5).…”

Expansion and impact of cassava brown streak and cassava mosaic diseases in Africa: A review

“…Prior to first report of CMD outbreak in Cambodia, a study conducted in 2016-2017 on the movement and exchange of cassava planting materials in Cambodia and Vietnam within communes found 82 and 78% of seed provided to others being exchanged between family and acquaintances, respectively (Delaquis et al, 2018). Similarly, in some African countries including Zambia were cassava is mostly grown by small scale farmers, frequent seed exchange occurs between farmers (94%) in the same or nearby communities (Szyniszewska et al, 2021). A similar study in Rwanda indicated that majority (76.9%) of the farmers obtain cuttings for free from either their own fields or from neighbors (Nyirakanani et al, 2021).…”

“…Cassava seed systems in Africa are largely farmer driven with low seed quality controls. Re-use of the farmer's own seed supply remains the most common source of seed (Kidasi et al, 2021;Szyniszewska et al, 2021).…”