a1 IRAD, PRASAC-ARDESAC, Cotton Program, Garoua, Cameroon
a2 CIRAD, UPR Annual Cropping Systems, Montpellier, F-34398 France
In sub-Saharan Africa, the bollworm complex, including Helicoverpa armigera, Diparopsis watersi and Earias spp., threatens the continued success of cotton production. Pyrethroid resistance in H. armigera led to serious crop losses while endosulfan, a suitable alternative to pyrethroids, was banned for cotton pest management. Five candidates with no cross-resistance to pyrethroids were evaluated in both on-station and on-farm trials from 2002 to 2006. Two applications were made at the early peak of H. armigera infestation in September, the period when pyrethroid use should be restricted for resistance management purposes. Results showed that, as expected, bollworm infestation consistently peaked from mid-September to mid-October. Spinosad, thiodicarb and emamectin-benzoate were the most suitable alternatives to reduce damage, regardless of the cotton bollworm species. Indoxacarb and lufenuron were less effective in controlling D. watersi. On-farm experiments confirmed the suitability of spinosad for control of pyrethroid-resistant H. armigera, particularly on late sown fields. These new chemistries offer control of bollworms which justify their relevance for pyrethroid resistance management in Cameroon and sub-Saharan Africa.
(Accepted September 22 2008)