The groundbreaking work of Pantenius (1988) and the other results presented in Section 5.1 above provided concrete figures on losses that underscored the necessity of stored product protection measures. However, there were only few indications for quantifying the socio-economic impacts of stored product protection upon small-scale farming systems and thus upon the standard of living of farming families.
Henckes (1992), Albert (1992) and Mutlu (1998) undertook further steps towards studying the importance of storage pests in small-scale farmer households. Henckes (1992) studied the damage and loss situation in maize stores in northern Tanzania with particular regard to the LGB, with the goal of developing an integrated control approach. He made the link for the first time between maize damage and losses and economic losses, by surveying data on the acceptance of consumers and on the connection between maize quality and price on local markets (cf. Box 4).
In all of the studies on post-harvest losses reported here, only slight economic losses were caused by storage pests, including the LGB, in the first three to four months of storage. Henckes (1992) introduced the concept of a damage threshold for his integrated stored product protection approach. He proposed dividing the harvest as follows:
· one part for consumption during the first months, which can remain untreated, and
· one part for long-term storage that is treated with a binary insecticide.
Henckes (1994) defined the current damage threshold over the respective quantities stored (untreated/treated) using the losses and market prices that are to be expected. However, in practice this approach proved to be too complicated, as the determination of these variables generally involves considerable effort. Nonetheless, this approach has been incorporated in a simplified form in the concept for integrated control of the LGB and associated storage pests.
Schneider (unpublished) is developing a method that will allow a prediction of pest infestation and losses for defined regions.
Box 4: Economic losses caused by the LGB in Tanzania In a study carried out from 1988 to 1991, Henckes (1992) identified the following damage to and losses of traditionally stored cob maize caused by the LGB in northern Tanzania: · In the 9th month of storage (without treatment) dry matter losses figured: - 31.8% for husked cob maize
· During this period of storage, the following economic losses arose: - 28% of the total value for cob maize
Interviewing revealed that farmers accept the consumption of maize with 6-20% dry matter losses (corresponding to 62-95% of the cobs being infested). · For cob maize, this means after a 9 month period of storage an actual loss of consumable maize amounting to 66.6%, i.e. double the loss in dry matter stated above. The maize offered for sale on the market only had 2% dry matter loss (with an infestation rate of 10%). This indicates stricter quality criteria for marketable maize and suggests that the economic losses are correspondingly higher again if maize is intended for sale. |
Albert (1992) undertook a comprehensive study of the farm economics of farm maize storage and stored product protection in southern Togo, in which he performed extensive model calculations. This study identified the benefits of 13 different combinations of storage techniques and stored product protection methods for three different types of farm.
The model calculations examined both storage of husked cob maize and of shelled maize. Storage in the dwelling, in traditional storage structures, in special storage rooms and in dry stores ("narrow crib") were compared. The protection techniques examined included the use of traditional methods such as ash, neem leaves and others, binary insecticides and an untreated variant. Box 5 states the main results and conclusions of this study.
Box 5: Farm management aspects of stored product protection measures in Togo* Albert (1992) examined the profitability of 13 different storage and stored product protection techniques for maize during three storage periods (1986-88) in farms in southern Togo. In a series of three tests of the loss situation he arrived at the following results for cob maize without treatment: · 1987 long season after 5 months of storage: 5-6%
In the 2nd and 3rd season, tests were also carried out on the impact of binary insecticides. The measured losses in these tests figured 0.5, 2 and 6%. Albert carried out model calculations on the cost-effectiveness of stored product protection measures involving the following factors: · Storage structure (dwelling, storage room, traditional store, dry store)
He assumed average losses in the 8th month of storage amounting to 14.4%. With continuous withdrawal of stored product, this corresponds to a total loss of 6% of the quantity put into storage. The main conclusions derived from the model calculations are as follows: · In general, storage costs (construction costs, storage materials and the labour involved in storage activities) are far higher than the costs of stored product protection measures.
* It needs to be kept in mind when considering these data that at the time of these calculations the LGB did not yet play a major role. |
In the context of a BMZ evaluation of the GTZ project on biological-integrated control of the LGB carried out in spring 1993, Schleich et al. undertook further calculations of the farm-level benefits of stored product protection measures in Togo. These examined four variants: traditional maize storage without protectants, traditional storage with application of a binary insecticide, grain storage in bags with insecticide application and biological control with Tn.
The authors arrived at the result that all four techniques are worthwhile for the farmer if the total quantity of maize consigned to storage (1.3 t) remains for 8 months in the store (which is not entirely realistic in practice). Due to the high efficacy of insecticides assumed in this calculation, their application yielded the best cost-effectiveness. This assumption did not however take into consideration that difficulties frequently arise in practice when applying insecticides. These difficulties lead to a lack of effectivity of treatment, which severely restricts the theoretically high level of efficacy of synthetic stored product protectants.
With the more realistic assumption of a continuous withdrawal of stored product, the cost-effectiveness of all four techniques was considerably reduced, biological control then being economically equivalent to insecticide application.
The most recent examination of the farm-level cost-effectiveness of controlling the LGB with Tn is contained in the project progress review report of Krause & Mück (1996). This calculation is based on data from the relatively well studied southern parts of Benin, Ghana and Togo. The report arrives at a positive result for the farms, as the biological control technique using the beneficial insect Tn does not burden the farmers with any costs, while yielding them a gain due to the reduced storage losses of maize and cassava chips. This calculation did not consider any regional or seasonal deviations. Box 6 contains the details of the calculation.
Mutlu (1998) places the small-scale farming system and thus the rural families at the centre of her analysis. The goal of her study was to check the efficiency of the beneficial insect under field conditions (cf. Box 3) and to analyse the socio-economic impacts of biological pest control upon small-scale farming systems in southern Togo (cf. Box 7).
Box 6: Farm-level cost-effectiveness of biological control of the LGB in the coastal region of West Africa Krause & Mück (1996) presented a calculation of the farm-level cost-effectiveness of the control of the LGB with Tn in the south of Benin, Ghana and Togo. They proceeded from the following assumptions: · Average quantity of maize stored per farm unit: 1 t
Under these conditions each third farmer runs the risk of suffering storage losses worth approximately 50 DM per year.
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Comparison of the approaches taken by Henckes (1992, 1994), Albert (1992), Schleich et al. (1993), Krause & Mück (1996) and Mutlu (1998) still leaves a number of questions unresolved. It can be derived from the interviews carried out by Henckes on the consumer acceptance threshold that the economic losses caused by the LGB are in fact higher than a simple conversion of dry matter losses to monetary units might suggest. The statements derived by Albert from the examination of the small-scale farming system show that in individual cases losses can be so unimportant that post-harvest protection measures for maize are not profitable. The calculation carried out by Krause & Mück (1996) underscores the economic benefit at the individual farm level of biological control of the LGB, but does not consider details of the two storage periods, consumer preferences, seasonal price fluctuations and other framework conditions (cf. Box 6). The systems approach of Mutlu (1998) suggests a relatively small impact of protecting stored maize upon the profit realized by rural households, but highlights at the same time the major importance of stored product protection for the economic security and the provisioning of families, and for environmental protection and resource conservation in general.
Box 7: Socio-economic impacts of biological control of the LGB upon small-scale farming systems in southern Togo In the period from 1991 to 1993, Mutlu (1998) carried out five on-farm tests with maize stores and standardized household interviews in 162 farms in the coastal region of Togo. The results can be summarized as follows:
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Despite the differing approaches, the following tendencies can be derived from the cited studies:
· The threat posed by the LGB to stored produce varies from region to region and from year to year.
· Monetary losses cannot always be calculated simply on the basis of dry matter losses, as the detrimental impact of infestation on the state of the product can also influence market prices (such as e.g. in Tanzania and Ghana).
· The profitability of stored product protection measures depends above all upon socio-economic conditions. This means that differentiated examinations are necessary for specific regions and farming systems, and across-theboard statements cannot always be made. Most farms must take individual decisions.
· The biological control of the LGB is worthwhile for farmers, and is economically and ecologically beneficial over the long term as it restricts the use of synthetic protectants to exceptional cases.
Seasonal price fluctuations and the associated (right or wrong) selling decision can have a stronger influence on the cost-effectiveness of maize storage than stored product pest infestation. It is therefore necessary within the systems approach (cf. Section 9 below) to collect further information on socio-cultural and economic factors from farmers, traders and consumers in order to properly answer the question of the profitability of stored product protection measures and in order to be able to give the correct extension recommendations.