ABSTRACT Laboratory and field experiments was conducted to evaluate the toxicity of two biocides i.e. onion oil and byrovect (mixture of Bacillus thuingiensis var kurestaki and Spodotera littorales NPV) against Pectinophora gossypiella (PBW) and Earias insulana (SBW). The LC 50 & confidence limits (95%) for values of onion oil and byrovect after 2 hours, 2 days and 7 days of treatment were determined. Moreover, the biological effects of LC 50 of the onion oil against pre-adult and adult stages of PBW were studied. Also, the two biocides and Chlorofet EC (48%) (As a chemical insecticide) were evaluated in Qalyoubia Governorate cotton field, individually (each one alone in sequence of 4 applications) as well as the three compounds in 2 different sequences program against cotton bollworm complexes, SBWand/or PBW. Present results cleared that the sequencing spray of onion oil (1 spray), chlorofet EC (48%) (2 nd spray) and byrovect (3 rd spray) was the most effective program against the PBW cotton boll infestation and larval content. In this respect chlorofet EC (48%) individually revealed high potential efficacy against SBW and boll complexes. st