Effectiveness of Maize Cob Powder in Controlling Weevils in Stored Maize Grain

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Abstract: The broad objective of this study is to assess the effectiveness of maize cob powder in controlling maize weevils in stored maize grain. A completely randomized block design, in which twelve small bags of maize containing 0.5 kg of maize grain (SC5313 dent variety), were used. Three concentration levels of maize cob powder 5g, 45g and 75g per 0.5 kg were compared with the control experiment containing conventional chemical Actellic super at 5g. Findings showed that conventional chemical control was more effective than traditional method at 5g and 45g levels of maize cob powder. However, greater effectiveness of cob powder was observed at 75g level. In the absence of conventional methods of control, which are unavailable due to local supply bottlenecks, the study recommends use of maize cob powder to control weevils.



The importance of the maize sub sector within the Southern African Development Community (SADC) region is well researched and documented. Maize is an integral component of the staple diet of the citizenry of this region and is also considered to be an essential source of cash for farmers. (1) It is also used in the manufacture of a wide spectrum of industrial products ranging from animal feeds to food products. Thus, the maize sub sector has important backward and forward linkages with industry.

In recent years, the region has witnessed dramatic changes in rainfall patterns ushered in by global warming that culminated in more frequent droughts. (2) The effect of intermittent droughts has manifested itself in declining maize output, further exacerbating the livelihoods of farmers and the general populace. The effects of poverty largely stem from the failure of agriculture to sustain the lives of the rural poor. It is therefore not a surprise that the majority of the families in SADC live on less than $1 per day. (3)

Declining food production exposes farmers to chronic and transitory food shocks. This creates the need for farmers to come up with mechanisms for conserving their scarce food resource base. Maize, which is normally stored in granaries, is usually treated with a different array of chemicals for preservation against pests such as weevils. Indeed, weevils (stophilus zeamais) are often identified as one of the major problems causing loss of stored grain in Africa. (4) It is estimated that weevil attack accounts for approximately 5-10% of maize grain loss in Southern Africa. (5)

In Zimbabwe, two main chemicals--Shumba and Actellic Chirindamatura Dust--are used to conventionally treat stored maize grain. (6) However, the inimical macro-economy has resulted in high prices for these products and the need for identifying other methods of preserving maize grain. One port of call for rural farmers is using localized methods of preservation found within indigenous knowledge systems.

Indigenous knowledge is unique to a given culture or society. (7) It creates the basis for local level decision-making in agriculture, health care, food preparation and preservation, education, and natural resource management. Indigenous knowledge is an important ingredient for development but is grossly under-utilized. (8)

A cocktail of methods, extracted from local knowledge, have been used to preserve maize grain for generations in Zimbabwe. However, one of the most eminent "indigenous approaches" of maize preservation is using maize cob powder. After shelling maize, the remnants are burnt and the resultant powder is sprinkled on maize grain and this confers longevity to maize grain.

This method can be questioned from two angles. Firstly, to what extent does this method improve the shelf life of stored grain? Secondly, does the resultant soot from burnt cob powder discolor the maize grain or render it unfit for human consumption? Thus, the crux of the matter in this study is to broadly look at the value of local knowledge in preserving stored maize grain. …


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