From the economic point of view and in terms of protection of the natural resources, it is much more reasonable to protect harvested produce against loss than to invest in further increases of the agricultural production. According to investigations made by GTZ 5 to 30 % of the African maize and cassava harvest is destroyed after six to eight months of storage by stored product pests. The losses depend on the storage system and the presence of the Larger Grain Borer (LGB), which is particularly devastating. According to FAO statistics the overall production of maize in Africa is 36 million t per year. Taking into account that three quarters of the total harvest are stored at farm level, the minimum losses amount to 1.35 million t every year. Much of these losses can be prevented using integrated post-harvest protection measures.
Integrated post-harvest protection on the farm level means the selection of appropriate measures according to the specific situation on every single farm. Integrated post-harvest loss prevention combines profitability with the protection of the natural resources. There are various possibilities to reduce or completely avoid the use of chemical stored product protectants. It is the task of the farmers and the extensionists to analyse the needs carefully before choosing the measures that suit them best. Criteria like simplicity, availability, cost, labour expense must always be taken into account. In this context, the extension brochure is intended to contribute to post-harvest loss reduction and to the improvement of food security.
However, there is a high demand for ready-made Integrated post-harvest packages which can be transmitted to the farmers in a Top-down approach. Such approaches will invariably fail, because they do not take into account the socio-cultural and economic conditions which vary from case to case. The present leaflet cannot cover all these conditions. Instead, it gives an overview of commonly practiced methods and measures to control the LOB and other stored product pests including the prevention of mould development. Methods which do not include the use of synthetic insecticides are particularly recommended in this leaflet.
Improved post-harvest protection allows the farmers to profit from the annual fluctuations of the market prizes by selling quality products at the time when the prizes are high. By this the farmers can considerably increase their incomes, because the price fluctuations are often much more important than the monetary value of post-harvest losses.
The contents of the leaflet are presented in a matrix which provides a quick access to the relevant information. The single elements included must be combined by the users of the leaflet in order to form integrated stored product protection schemes that meet the above mentioned requirements.
The leaflet is primarily directed to extension workers and subject matter specialists who are the main transmitters of agricultural innovations. The methods and measures listed below may concern different target groups. Therefore, the target groups are indicated in the matrix using the following abbreviations:
DM Decision makers
FA Farmers
SM Store managers
AP Applicators of insecticides to protect stored products (commercial and
private)
WO Women in rural households
The numbers indicated in the column "Info" refer to the publications listed under "Further information at the end of this leaflet.
| Nr. | Methods and measures | a) Potential for application | b) Instructions and recommendations for the application | c) Effects on the target organisms | d) Observations and combination with other measures | Info | Target groups | Environmental considerations | ||||
| DM | FA | SM | AP | WO | ||||||||
| 1 | Selection of tolerant varieties | Maize stored on the cob are with husks in traditional storage systems. No information available on cassava | Grow varieties with cobs which completely covered by the husks. Traditional varieties generally fulfil this requirement, but new varieties may be preferred by the farmer because of their high yields Select only undamaged cobs for storage (see measure 5). | Husks which cover the whole cob prevent most stored product insects from attacking the maize cob | Fully covered cobs show generally less damage by the LGB than others How ever, this pest is not sufficiently controlled, if this method is not accompanied by additional measures like 2, 4, 5, 6, 7, 8, 9, 11, 13 and 14 | X | X | This measure does not have any negative impact on the environment or human health | ||||
| 2 | Timing of the harvest | Maize and cassava to be stored under all kinds of conditions | Do not harvest before the time of physiological maturity, but avoid as well late harvest. Maize is ready for harvest when the grains are hard and vitreous with a black spot at the base. For cassava the maturity is more difficult to determine. Maturity is always a function of the variety. | Maize harvested at the right time has an optimum storability and resists better against insect and mould attack. Cassava gives best yields at maturity. | Maize which is harvested before maturation will rot quickly, while late harvest often leads to field attack by certain stored product pests including the LGB which will be brought to the store together with the harvested produce. This measure is one of the prerequisites for a good storage and goes together with all other methods. | X | X | This measure does not have any negative impact on the environment or human health | ||||
| 3 | Dehusking and shelling | Maize stored In bags or hermetically sealed containers | Dehusk and carefully shell maize immediately after harvest. Store it in hermetically sealed containers (see method 10) or add a recommended stored product insecticide (see methods 12 and 13) and store the maize in bags. | By shelling and using additional protective measures the development of pests hidden inside the cobs (especially the LGB) can be prevented. | Avoid breaking of grains during shelling in order to prevent attack by moulds and secondary insect pests. Loose grains are easily attacked by insects. Therefore further measures of protection are required (see 2, 4, 5, 6, 7, 8, 9, 10, 12, 13 and 14). | X | X | If synthetic stored product protectants are used additionally, refer to the remarks under 12. | ||||
| 4 | Correct drying | Maize and cassava chips be stored under all kinds of conditions | Different methods like drying in the open air or solar dryers can be used for maize and cassava chips. Dry until the safe moisture content for storage is reached (maize 13 %, cassava chips: 12 %). Stir the drying produce in regular intervals | Well dried maize or cassava chips will not be easily attacked by moulds which can produce dangerous mycotoxins sprouting will not occur in, sufficiently dried maize grains. | Avoid overheating of maize. The maximum drying temperature for seeds is 43°C. Maize for consumption can be exposed to temperatures of up to 60°C. Higher temperatures result in loss of germination, cracking of grains and loss of nutrients. Good drying is a further prerequisite for all other storage practices. | X | X | X | Sun drying and drying cribs do not have any negative impact on the environment. Good drying practices limit health hazards due to mycotoxins | |||
| 5 | Sorting and cleaning of the produce | Maize and cassava chips stored under all kinds of conditions | Select only maize cobs and grains or cassava chips without any visible damage for storage Separate any impurities including insects from loose grain by winnowing. | Sorting and cleaning eliminates a large part of the pest insects coming from the field. | While sorting watch out for all kinds of damage: insect infestation, mould and mechanical damage. Use damaged produce as soon as possible. Sorting and cleaning goes with all other methods | X | X | X | These measures do not have any negative impact on the environment or human health. | |||
| 6 | Cleaning and repair of storage facilities | Storage facilities and containers for all kinds of produce | Remove any remnants of produce from containers before storing the new harvest Clean containers and rooms thoroughly with a broom Repair cracks and holes in the walls. Clean the surroundings from dirt, rubbish and tall plants. Burn the rubbish. | Cleaning and repair of storage facilities eliminate pests and destroy their hiding places. Cleaning of the surroundings keeps rodents off the store. | Insects often hide in remnants of old stocks or small cracks and holes and can infest the new harvest if no storage hygiene is practiced The rubbish must be burnt to make sure that tiny pests hidden in-between are destroyed. Rodents avoid unsheltered open areas. Such hygiene measures should always accompany all other methods. | X | X | X | These measures do not have any negative impact on the environment or human health. | |||
| 7 | Rodent guards | Traditional granaries based on wooden poles | Wrap sufficiently wide metal sheets tightly around each pole of the granary in order to obtain a kind of sleeve with a minimum length of 30 cm. These sleeves must be nailed to the poles at a height of 1 m above the around. | These simple devices prevent rodents from climbing up the poles and entering the granary. | The indicated measurements must be observed carefully, as many rodents can jump very high and overcome guards that are fixed too low. Rodent guards can complement the measures 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 13 and 14. | X | This measure does not have any negative impact on the environment or human health. | |||||
| 8 | Improved granaries | Traditional granaries of the ,,kihenge" type | Plaster the inside and outside surfaces with mud, provide a lid and an outlet at the base and fix rodent guards to the supporting structure of the kihenge. | In an improved kihenge the produce is better protected from all kinds of damage and handling is facilitated. | Take care that the kihenge is solidly constructed so that it will last long. Inspect it regularly in order to detect and repair any damage immediately. Combine with methods 1, 2, 3, 4, 5, 6, 7, 9, 11, 12, 13 and 14. | X | X | This measure does not have any negative impact on the environment or human health. | ||||
| 9 | Traditional grain protectants | Maize in traditional granaries. For cassava chips no methods are known. | i) Add mineral dusts in locally
used proportions ii) Add material of plant origin (leaves, powders, oils, ashes and others) according to local customs iii) Smoke the produce (e.g with hot pepper) |
Many traditional methods of stored product protection deter insect pests or restrict their development | Most traditional methods are not as effective as a treatment with synthetic products, but they contribute to a certain degree to the control of storage pests. They are easily available and cheap and can be used in combination with methods 1, 2, 3, 4, 5, 6, 7, 8, 11, 13 and 14. | 1 2 3 |
X | X | Natural substances are generally environmentally safe However, some of the plant materials can be toxic to human beings. | |||
| 10 | Hermetic storage | Storage of well dried maize in semiarid and arid areas | Fill maize grains in well cleaned oil drums or similar containers and close them tightly. Keep these containers in a shady place, preferably indoors | Pest insects in the container die soon because of lack of oxygen and intoxication with carbon dioxide. | This method is particularly recommended in dry areas if the maize is too humid condensation occurs due to temperature fluctuations and there is a high risk of rotting. Use together with 2, 3, 4, 5, 13 and 14 | X | X | This measure does not have any negative impact on the environment or human health | ||||
| 11 | Biological control with Teretriosoma nigrescens (T.n.) | Control of the LGB in maize and cassava chip storage | The predatory beetle Tn., a beneficial insect which has been introduced from Central America, is released in the field by qualified plant protection agents in areas infested by the LGB. It multiplies and spreads on its own and searches actively the LGB on which it feeds exclusively The release campaigns involve surveying of the LGB populations, importation and mass rearing of T.n., repeated releases in areas with high LGB populations and follow-up studies in order to evaluate the impact. In Tanzania the preparations for the biological control of the LGB started in 1996. | The larvae and the adults of T.n prey on the LGB and lead to a considerable decrease in population. This beneficial insect actively finds granaries infested by the LGB. T.n. finds most of its prey the wilderness, where the LGB often is present the wooden parts of shrubs and trees. | The biological control of the LGB is a task of the national plant protection authorities. The farmers have the profit, but no additional cost or work. The effectiveness of T.n and safety aspects have been studied before the introduction of T n to Africa in order to ensure the success. After the first releases in 1991, the active distribution of T.n., its effect on the LGB populations and a significant in loss reduction in stored maize have been monitored and confirmed. Biological control works together with methods 1, 2, 4, in 5, 6, 7, 8, 9, 13 and 14. | 4 5 6 7 |
X | X | The biological control of the LGB contributes to re duce the amount of insecticides used in stored product protection and has thus positive effects on the environment and human health. Tests showed that T.n. does not damage the stored product and does not menace beneficial insects (e.g honey bees) or the indigenous insect fauna. | |||
| 12 | Application of synthetic stored product protectants | i) Maize for storage over longer periods (more than 3 to 4 months) ii) Granaries, storage containers and bags Suitable for the protection of shelled maize and, to a lesser extent, cobs with husks in traditional granaries Excellent for seed protection | i) Shell the maize and treat
it with a recommended insecticide according to the manufacturer's instructions.
In Tanzania Actellic Super Dust is the only available product for stored
maize protection. Add the officially recommended dose of the insecticide
dust to the maize and mix it thoroughly. Observe the safety instructions
carefully Do not experiment with higher or lower dosages or products like
seed protectants for treatments of maize for consumption: ii) Treat the inside walls of the granaries and storage containers or the bags with a thin layer of the stored product insecticide |
Synthetic products provide a good protection against insect pests in stored maize due to their strong and lasting insecticidal effect. . | Synthetic insecticides can be recommended when their application is of economic advantage for the farmer. This is only the case for storage longer than 3 to 4 months. Buy only the amount of insecticide required for one season from an authorised dealer and use it soon because of the limited shelf life of these products. Reject old, dirty or torn packages and lumpy products. The success of the treatment depends on the right dosage and even distribution of the product. The effect is best in shelled maize. Treatment of maize on the cob has inferior results. The combination of insecticide treatment with the measures 2, 3, 4, 5, 6, 7, 8, 13 and 14 is recommended For cassava chips no satisfactory application techniques have been developped so far | 8 9 10 11 |
X | X | X | If synthetic stored product protectants are applied by inexperienced farmers, there are considerable risks for the health of the farmers and the consumers, which can be intoxicated with elevated dosages or inappropriate products During application, pollution of the soil or ground water may occur If the application is done according to the prescriptions, the risks are very low. | ||
| 13 | Dividing the harvest | Maize for home consumption and for selling | This method is based on dividing the harvest in a part for home consumption within 3 to 4 months and another one for longer storage. The first part is not treated with a synthetic insecticide, because the stored product insects do not term cause significant damage during this period. Only the second part is shelled and treated following the instructions given above (12 b). Observe also the remarks in 5d | Dividing the harvest before insecticide application provides maximum protection of stored maize on a long following the same principles as described in 12 c). | Dividing the harvest is especially attractive for farmers who to sell the surplus of their maize harvest at a later time, when the prices are high. They can treat only the part of the maize harvest which they want to sell and achieve a considerable reduction of the cost of treatment, as the portion for home consumption is stored under traditional conditions. Combinations with 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 14 are possible. Method 12 is al ways Part of dividing the harvest. | 8 | X | X | X | Dividing the harvest contributes considerably to the reduction of the use of insecticides. As far as the risks are concerned, see method 12. | ||
| 14 | Surveillance of the store and the produce | All storage structures and stored products | Inspect the storage rooms, granaries or containers including the surroundings and the stored produce regularly, at least once a week. Watch out especially for signs of damage to the structure like a leaking roof, that might expose the produce to moisture or pests. Watch out for traces of the presence of rodents, for living insect pests and for the development of mould. ` | Surveillance does not have any direct impact on pest organisms. however, timely detection of any damage to the storage marks, structure and of the presence of pest organisms increases the impact of any measure of loss prevention. | Whenever a damage to the storage structure is detected, repair it immediately in order to avoid further damage to the store and the produce. The presence of rodents can be detected through traces like droppings, gnaw spilled grain, etc. Insects can often be watched directly, especially at dusk In case of infestation take immediate measures to prevent further losses (e.g. drying, cleaning, quick selling). Surveillance goes together with all other measures. | 11 | X | X | X | This measure does not have any negative impact on the environment or human health | ||
Flow chart of integrated stored product protection measures
Special extension leaflets and brochures on some of the measures listed in this matrix have been published by this and other post-harvest projects of GTZ. They are listed below under the numbers appearing in the column "Info" of the matrix. These publications can be ordered free of charge from the adresses given in the preface of this leaflet. The languages in which they are available are indicated in brackets.
Elaborated by
GTZ/Tanzania Project. for Integrated Control of Storage Pests
Ministry of Agriculture/Plant Protection
Mr. Y. B. Nyakunga/Mr. W. Riwa
P. O. Box 9071
Dar es Salaam
and
Deutsche Gesellschaft für Technische Zusammenarbeit
(GTZ) GmbH
Project "Integrated control of the Larger grain borer in farmers' post-harvest
systems"
Mr. Albert Bell, OE 4232
Postfach 5180
D-65726 Eschborn
Germany
E-Mail: albert.bell@gtz.de
with input from
Otto Mück, Post-harvest consultant, Hamburg, FRG
Financed by
Bundesministerium für wirtschaftliche Zusammenarbeit und Entwicklung
German Federal Ministry for Economic Co-operation and Development (BMZ)
