Environmental and economic impacts of pesticide treatment in the Yam Minisett Technique

Abstract

White yam (Dioscorea rotundata) is an important tuber crop in a number of countries, but especially in West Africa where it serves as a food staple as well as a cash crop as excess production is sold in local markets. But the availability of quality planting material, most notably seed yams, for yam production remains an important constraint for farmers. Techniques have been developed to help address this limitation by cutting yam tubers into pieces (minisetts), treating them with the pesticide either via a seed dressing dust or pesticide ‘dips’ and planting to grow seed yams of the required size and quality. But while there have been many studies on the agronomy and adoption by farmers of these techniques, there have been fewer studies on their economic performance. Indeed, to date there have been no studies that compare the economic performance of treating setts compared to leaving them untreated, and neither has there been any analysis of the environmental impact of treating setts. This paper reports the results of a study designed to address these two gaps in knowledge and is based upon results from a series of farmer-managed seed yam plots established in the middle belt of Nigeria over 4 years (2013–2016). Results suggest that revenue and gross margin were higher for treated versus untreated setts although the latter still performed relatively well. Using the Field Use Environmental Impact Quotient (EIQ), the commonly recommended pesticide sett treatments were estimated to have a low-to-moderate environmental impact, and further research is needed to see how far pesticide use can be reduced to still be effective and minimise any environmental impact.

The role of plant health in the sustainable production of seed yams in Nigeria: A challenging nexus between plant health, human food security, and culture

“…Flooding in riverine areas, places where growing yam is especially beneficial given the soil fertility and water availability, can result in complete losses of the crop as indeed can damage by the cattle of migratory pastoralists (the Fulani). The large size and relative fragility of tubers makes them vulnerable to physical damage during harvesting and transportation to storage, and the crop also suffers from a range of foliar and tuber pests and diseases (Morse, 2018(Morse, , 2020.…”

“…lindane, aldrin) and fungicide (e.g. thiram), often mixed with wood ash (Morse, 2020), although the effectiveness of woodash in the mixture has been questioned (Onwueme and Charles, 1994). <Figure 2 near here>…”

“…There have also been studies on the agronomic impact of using seed yams produced from AYMT on subsequent ware yam production (Morse & McNamara, 2017) as well as the technical efficiency of both ware and seed yam production under farmer-managed conditions in Nigeria (Morse, 2021). An example of one of the studies of clean seed yam production designed to explore the agronomic impact of pesticide dip applied to minisetts in AYMT is provided by Morse (2020). The work reported in this study was based on a series of demonstrations of AYMT in the middle-belt region (Benue and Kogi States) of Nigeria and was part of the YIIFSWA Phase I project listed in Table 2.…”

“…Pesticide costs are in themselves a relatively minor aspect of seed yam production, as illustrated in Figure 4, which has also been based on the data employed in Morse (2020). The major costs in seed yam production are labour and planting material, which together account for some 95% of the total costs.…”

“…The graph is based on data presented in Morse (2020) one other cultivated plant that arguably comes close to this is the oil palm (Elaeis guineensis). But from the perspective of the farmer, yam is a challenging crop to produce, transport, and store, and there are significant risks involved, especially given the potential for losses to pests and diseases.…”