Control of the African Armyworm Spodoptera exempta Walker (Lepidoptera: Noctuidae) in Kenyan Fields with Highly Effective Strains of Bacillus thuringiensis Berliner

Good control ofsecond and third instar larvae ofSpodoptera exempta was obtained in cereal fields using spray application ofpowder preparations ofdifferent Bacillus thuringiensis (Bt) strains: Bt24 (var. entomocidus), IH-A (var. aizawai) andK26-21 (new isolate). These Bt preparations also protected cereal cropsfrom damage caused byfourth to sixth instar larvae, but lower rates of larval mortality were obtained (50% 80%). Spray applications of Bt preparations combined with a ‘sweeping out’ operation using a Californian sweep net in grass fields surrounding susceptible crops, were shown to be effective in preventing massive migration of large larvae to the crops, especially in smallfarms. copyright