INNOVATIVE APPROACHES IN THE CONTROL OF QUELEA, Ouelea auelea lathimii. IN ZIMBABWE

Ever since crops have been grown, quelea have been a threat to summer subsistence crops and winter commercial wheat/barley cropping in Zimbabwe. Control techniques spraying toxicant Queletox through ground spray units and aircraft, developed in Zimbabwe, have produced 90% kills keeping the level of depredation down to acceptable levels. Zimbabwe, like most developing countries, faces protein shortages, and utilization of dead quelea by the rural population has always occurred even from sprayed colonies despite repeated warnings of possible side effects. Traditionally quelea have been sold on the black market for 10-20 Zimbabwe cents/bird and recently a far wider potential, even export, has been realized with a potential value increased to 40 cents/bird. Several applications for permits to harvest large numbers have been processed by the Department for export and local consumption provided a suitable method of capturing large numbers could be perfected. The recognition of quelea as a potentially economic renewable resource has intensified research in this area and several mechanical systems have been tried over the years finally culminating in the promising development of the "Impact" trap. The method potentially provides large numbers of uncontaminated quelea for the market. With careful monitoring and the parallel development of the trap roost concept, it is possible this approach could also sufficiently reduce toxic control beneficial to the environment as a whole while providing a source of food and revenue to Zimbabwe. Proc. Vertebr. Pest Conf. (A.C. Crabb and R.E. Marsh, Eds.), Printed at Univ. of Calif., Davis. 13:310-314, 1988 INTRODUCTION AND BACKGROUND The southern race of quelea, Ouelea quelea lathimii. breeds largely outside Zimbabwe, to the south, west, and in the north where conditions are arid, ideally suited for breeding (Ward 1971). Most of the border areas in Zimbabwe form part of Parks and Wild Life Estates; however there are some communal lands adjacent to the border which experience quelea damage to summer subsistence small grain crops. Greater concentrations of quelea occur during the winter months when the birds congregate in large roosts often numbering several million adjacent to commercial irrigated wheat/barley crops. Unlike most other African countries, which do not have sophisticated irrigation facilities, damage is more noticeable at this time and tremendous effort and expenditure over the last 20 years has led to the development of effective aerial and ground methods resulting in greater than 90% kills regularly being achieved using the toxicant Fenthion (La Grange 1978). Studies in Zimbabwe, based on work originally carried out in Botswana (Jones 1975,1976), has shown strong correlations between the level of depredation, presumably indicative of the birds' status, and the previous season' s rainfall. Where good rains are experienced over a long period quelea appear capable of breeding several times with greater numbers threatening crops the following season. Observations in Zimbabwe indicated that this correlation occurs irrespective of control measures implying that in the long term they have no effect upon seasonal numbers (La Grange unpublished government reports). Consequently, since 1980 Zimbabwe has adopted an approach to control only those quelea which are a direct threat to the standing crop. At the Quelea Symposium in Nairobi in 1986 this approach was similarly adopted as a general resolution by most African States. Seasonal rainfall has become reasonably reliable as a source to predict the following season's quelea problems, although there are further factors which need to be clarified: for example, the degree of grass cover, particularly annual species, still standing at the commencement of winter which the birds seem to prefer (Jarvis and Mundy, in press). Research findings indicate that grass seed is preferred except possibly sorghum, particularly the white varieties. The percentage of the birds observed in lands actually feeding upon wheat and barley appears relatively small. All the samples taken from the wheat lands where the birds were apparently feeding upon them indicate only one-third of the population feeding on the crop, the remainder preferring Panicum spp. grass growing within the crop. Studies of wheat damage have indicated low levels of depredation, less than 5%, even where no control is effected, leading to the conviction that damage claims in respect to wheat are probably overrated; and should effective protection methods be devised, lethal control would no longer be necessary. It is admitted, though, that damage is more serious to barley and can be devastating to sorghum and millet during the summer months. Unfortunately pilot studies in Zimbabwe using both repellents Trimethiocarb and Methicarb did not indicate repellency for more than 3 days; however, it is possible that the mode of application could be improved (Bruggers pers. comm.). ARGUMENT FOR HARVEST POTENTIAL Africa experiences an acute shortage of protein food and any source of protein must therefore be exploited. Traditionally in Zimbabwe quelea have always been harvested by various means using sticks to beat roosts after sunset or elastic strips from inner car tubes to smash through birds