8 th European Vertebrate Pest Management Conference 130 Julius-Kühn-Archiv, 432, 2011 Environmental impacts of the control with organophosphate pesticides and explosions of the red-billed quelea bird Quelea quelea in Africa Cheke, R.A. 1 , Van der Walt, E. 2 , Mbereki, C. 3 , Mtobesya, B.N. 4 , Magoma, R.N. 5 , Farman, D.I. 1 , Adranyi, E. 1 , McWilliam, A. 6 1 Natural Resources Institute, University of Greenwich at Medway, Central Avenue, Chatham Maritime, Kent, ME4 4TB,UK, r.a.cheke@greenwich.ac.uk 2 Agricultural Research Council, Plant Protection Research Institute, P. Bag X134, Queenswood, 0121, Pretoria, Republic of South Africa 3 Plant Protection Division, Ministry of Agriculture, P/Box 0091, Gaborone, Botswana 4 Plant Health Services, Ministry of Agriculture Food Security and Cooperatives, P.O. Box 9071, Arusha, Tanzania 5 Plant Health Services, Ministry of Agriculture Food Security and Cooperatives, P.O. Box 9071, Dar es Salaam, Tanzania 6 The Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, U DOI: 10.5073/jka.2011.432.072 Abstract Both spraying with pesticides and using explosions to kill red-billed quelea (Quelea quelea) may affect non-target organisms and leave hazardous contaminants in the environment. Results of monitoring such effects in Botswana and Tanzania showed that although few non-target mortalities were noted, indirect effects in terms of depressed cholinesterases in birds and small mammals were marked and pesticides and contaminants from products used for the explosions persisted at controlled sites at unacceptable levels and for long periods (at least 188 days for sprays and at least 11 months for petroleum products and plastics). Keywords: cholinesterases, explosions, non-target organisms, organophosphate sprays, Quelea quelea L., red-billed quelea, residues Introduction The red-billed quelea Quelea quelea is a major pest of small grain cereals in sub-Saharan Africa (Bruggers and Elliott, 1989). The birds nest colonially and also roost in dense concentrations, providing targets that can be controlled by spraying with organophosphate avicides, such as fenthion and cyanophos, or by explosives. Some environmental impacts of these lethal methods used against Q. q. lathamii in Botswana and Q. q. aethiopica in Tanzania were investigated. Mortalities of non-target organisms were recorded after control operations. The blood cholinesterase levels of non-target birds and small mammals were monitored and soil residue analyses were conducted on samples after sprays with fenthion or cyanophos and after explosions. Pesticide droplet sizes and deposition were also studied. Materials and methods (a) Sprayed sites. Soil samples of approximately 200 g (maximum depth 10 cm) were collected at 7 sprayed sites in Botswana and 4 in Tanzania and residues of fenthion or cyanophos detected by GCMS. As blood cholinesterases are depressed by the action of organophosphates, we used custom-made field kits using the Ellman reaction (Ellman et al., 1961, Test-mate kits, EQM Research Inc., Cincinnati, USA) to analyse erythrocyte cholinesterase (acetylcholinesterase, AChE) and plasma cholinesterase (butyrylcholinesterase, PChE) levels in the blood of birds and small mammals caught before and after spraying. Droplet samples were collected on magnesium oxide (MgO) coated glass slides placed on metal sampling masts 1 m above ground level. (b) Sites of explosions. Soil samples were collected at 10 sites in Botswana before and after explosions of diesel and petroleum mixtures in plastic containers and levels of total petroleum hydrocarbons and plastics were detected by GCMS. Any dead non-targets were recorded and effects on the vegetation assessed visually. Results Spraying operations’ effects on non-target birds were confirmed by direct associations between non- target morbidity and the depression of blood cholinesterase levels by as much as 90%. Small mammal populations examined 6 weeks after aerial sprays in northern Botswana had significantly reduced blood cholinesterases. Fenthion had a half life of 47 days in soil, sometimes remaining at unacceptably high