Effects of insecticides on non-target organisms in African agroecosystems:a case for establishing regional testing programmes

Field trials were simultaneously conducted in Algeria, Nigeria, Tanzania, U ganda and Zambia between 1992 and 1995 in order to determine the effects of organochlorine pesticides lindane tall countries) and endosulfan (two coun tries) on cion-target arthropods in African maize agroecosystems. In additi on, a laboratory screening test was conducted to determine the initial toxi city's of several organochlorines and a synthetic pyrethroid to three speci es of non-target arthropods. Lindane significantly reduced the numbers of C ollembola in over 80% of the field trials for an average of six weeks. Simi larly, spiders were reduced in 53 % of the trials for an average of 2,8 wee k, and ants were reduced in 64% of the trials for an average of 2.5 week. T he lindane treatment significantly reduced organic matter breakdown in over 45% of the trials, whereas endosulfan had no effect. The latter had little or no effect on non-target arthropods. The lindane treatment significantly reduced plant damage in all countries. However, corresponding significant increases in yield were observed in less than 50%. There was an apparent co nsistent effect of lindane on different non-target groups as indicated by t he positive correlation's between these variables. Endosulfan was found to be harmless to all the non-target arthropod species included in the laborat ory screening tests. The order of toxicity was lindane = deltamethrin much greater than chlorpyrifos much greater than endosulfan. It is concluded tha t African countries need to develop procedures for testing pesticides in Af rica in order to arrive at the correct conclusions concerning adverse side effects from pesticide use. (C) 1999 Elsevier Science B,V. All rights reser ved.