Three bio insecticides Biolarve and Triamph derivate from emamectin benzoate  and W-Bus which derivate from Bacillus thuringiensis (Bt), in addition to one organophosphorus insecticides Linker tested for their effects on  2^nd and 4^thlarval instars and egg masses (24, 48 and 72 h old) of the Egyptian cotton Leafworm Spodoptera littoralis  (Boised) infested tomato crop under field and semi field conditions. The doses used were the recommended dose by Egyptian agricultural ministry. The obtained results showed that all insecticides were potent and effective in controlling S. littoralis caused highly mortality and reduced the number of all tested larval instars and egg masses. The bio pesticides caused lower mortalities percentage than the chemical one in case of initial kill calculations, but after one day till ten days caused higher mortalities percentage than the organophosphorus insecticides. The second larval instar recorded sensitive reaction than the fourth larval instar of S. littoralis, which shown more resistant to all examined insecticides.