|CERES No. 104 - March - April 1985 (FAO Ceres, 1985, 50 p.)|
Nearly four years after the alarm was first sounded by a group of farmers in the Tanzanian village of Itunda, a solution to the problem of how to deal with the invasion of the larger grain borer- a predator of the family Bostrychidae whose main tar gets are maize and cassava stocks an her-vests (see Ceres, Nov. Dec. 1982) is still far off. But while the dumunzi, as the Tanzanians call it, cannot yet be eradicated, measures are being taken to curb the havoc it causes an to stop it from spreading to other regions of the country and across the borders.
It is the vastness of the problem that poses the greatest challenge: the latest research findings indicate that this insect, which was unknown in Africa until a few years ago, has now become firmly established in the northern half of Tanzania. By August 1984, it had been reported in the border zones of Burundi and the extreme south of Kenya, and in earl 1985, it was found in West Africa, in the LomTogo) region. Although i is a winged insect, the data collected on it so far suggests that it is mainly propagated by being transported in maize and dried cassava, and probably in contaminated sacks.
No one is certain where the dumuzi originally came from, even though it is known in Central America, Mexico and the southern United States. But from the findings of the first surveys conducted in Tanzania by a team from the British Tropical Development Research Institute, we now know that it can cause grain losses of over 10 per cent, which means 10 per cent less grain available for consumption and sowing. Tanzania's aggregate annual potential maize loss in 1982 has bee put at 543 000 tons, worth several million dollars, working in conjunction with the programme officials, has shown that the most effective weapon against the dumuzi so far discovered is 0.5 per cent permethrin powder, of which 50 grams is enough to protect 90 kilos of matzo for about 10 months. But it is only effective if the farmers are prepared to break with tradition and husk them maize before storing it. This method not only requires them to adopt new storage techniques, but it also takes time, having to husk manually the 500 kilos that the average household farm produces imposes a heavy burden on all the members of the family, at precisely the time when they have to harvest tobacco and cotton, whose cropping cycle follows on the heels of maize. To overcome this problem, the far-mere have to use manual huskers so that the operation can be completed in a matter of days Research is being conducted to produce a husking machine that will meet their needs, and which can be manufactured locally.
After the 1984 harvest in the Tabora region, in the north of the country, it was found that dumuzi infestation was about half that in previous years. The experts felt that this decline was due to the fact that the 1983 stocks, which might have been a potential source of infestation, had been almost entirely disposed of. Many farmers have therefore decided to wait and see whether the insect reappears before husking their maize and buying permethrin. Yet in some of the villages, about half the small farmers who still vividly recall the disastrous situation they experienced in previous years have agreed to test out the new methods being proposed.
One of the main reasons for the success of this first campaign, apart from the fact that it has made inputs (sacks, insecticides) readily available, is the hard work put in by the extension workers, rural development officials, and agricultural produce inspectors at local and regional level. Just before the campaign started, about 900 of them went on crash courses lasting several days, run by regional supervisors and district storage officials, who had previously been given appropriate training. This programme is scheduled to be repeated over the next few months, and teaching aids (folders, posters, films, and videos on husking and storage techniques) are now being produced, and will be made available to the extension workers.
However, despite these encouraging results, there arc still a great many hurdles to overcome if the dumuzi is to be beaten. The sheer size of the region creates serious logistical problems (roads and vehicles), particularly the transport of materials and extension workers and stock supervision officials both on the farms and at the market. There is no immediate problem with supplying 0.5 per cent permethrin. In 1984, the Tanzanian Government bought 160 tons of insecticide that was re-packed in 30- and 50-gram packets The new maize storage techniques involve the use of sacks or woven baskets which can be produced locally, but if the new techniques are to catch on quickly, over a million more sacks will have to be made immediately available. A further problem is the fact that the dumuzi also attacks cassava when it has been dried and stored on the farm, and the researchers have not yet come up with a fully satisfactory method of protecting it.
While work is moving ahead in Tanzania, the bordering countries have to set about tackling the problem, now that they are aware of it. Just after the larger grain borer had been discovered in the border areas, a cooperation project was prepared in Burundi to initiate a campaign to control and combat this parasite. In Kenya and Togo, similar programmes have been set up with technical assistance supplied by the Government of the Federal Republic of Germany under its bilateral aid programmes.