Combination of modified atmospheres with high CO2 contentand volatile bioactives for the control of the rice weevil

Abstract: Current control of Sitophilus oryzae in grain cereals mainly rely on chemicaltreatments. Among alternatives, modified atmospheres (MA) are a safe and environmentallyfriendly pest control method, but sometimes are too slow for the requirements of the industry.Volatile bioactives (VB) based on aromatic plants are known to have insecticidal effect andfavourable eco-toxicological properties. Also, the use of Natural Enemies (NE) is recentlyreceiving attention as a pest control alternative during the storage of cereals. Advantages includethat NE are innocuous to end users and harmless to the environment, but the presence of any typeof ’insects’ at the end of the storage period should be avoided.In the present study, the combined use of a 50% CO2 MA and some VB have been assessedfor the control S. oryzae adults. Two essential oils (S-(+)-carvone and linalool) and one fatty acid(propionic acid) were tested. The results obtained showed that the mortality of S. oryzae causedby MA was enhanced with the addition of the three VB tested: the highest mortalities (> 99%)were obtained when insects were exposed during 72h to the MA in combination with 11.4mg/l ofS-(+)-carvone or 34.2mg/l of linalool or 34.2mg/l of propionic acid. Doses of linalool causing95% mortality in S. oryzae were also adequate to control two of its parasitoids, Lariophagusdistinguendus and Anisopteromalus calandrae. On the contrary, doses of S-(+)-carvone causing95% mortality in S. oryzae were not effective for the control of any of these two species.