Laboratory studies were carried out on the relative effectiveness of the extracts of nccin fruits and datura leaves under modified atmospheres on the mortality and percent: reduction in emergence of F, -progeny of the rust flour beetle adults. (Triholiunt caxttincuw), the rice weevil adults (Silnphilus oiyzac) and the adults and larvae of the khapra beetle (Tmgotierma grundHum) Two modified atmospheres. 21% CO:, (61 .6% N: + 15.4% CM and 47% CO:. (42 4% N; -t 10.6% O:) were used in combination with the aforementioned two plant extracts against of the three above mentioned adults in addition to another two atmospheres, 73% CO., (216% N- + 5.4% O:) and (100% CO2) against (he larvae of khapra beetle Results revealed that treatment of adults or larvae under test \ilh the two extracts in the presence of a modified atmosphere at various exposure periods increased mortality particularly, with the increase of exposure periods and/or extract concentrations where, the co-ioxicily factor increased gradually to change the antagonismic action at the lowei exposure periods and extract concentrations into potentiating or syncrgesmic action at the higher exposure periods and concentrations Total mortalities of adults and larvae were obtained at 4. X and 12 days exposure periods combined with increased CO concentration and decreased O, concentration Reduction ol emergence of F| progeny after 60 days of treatment reached to 100% in certain treatments