The use of modified atmospheres to control Sitophilus zeamais and Sitophilus oryzae on stored rice in Portugal Maria Otília Carvalho a, * , Inês Pires b , António Barbosa a , Graça Barros a , Jordi Riudavets c , Alfonso Camara Garcia d , Carla Brites e , Shlomo Navarro f a IPM on Stored Products - Pólo Mendes Ferrão, Instituto de Investigação Cientifica Tropical, Apartado 3014,1301-901 Lisbon, Portugal b Novarroz-Produtos Alimentares SA, Adães, Ul, Oliveira de Azeméis, Portugal c IRTA, Entomology, Ctra. Cabrils km 2, 08348, Cabrils, Barcelona, Spain d Carburos Metálicos S.A. C/Aragó n  300, E-08009 Barcelona, Spain e Unidade de Investigação em Tecnologia Alimentar e INRB, Quinta do Marques, Oeiras, Portugal f Food Technology International Consultancy Ltd., P.O. Box 3300, Bet-Yehoshua 40591, Israel article info Article history: Accepted 7 May 2012 Keywords: Stored rice Modified atmospheres Controlled atmospheres Sitophilus zeamais Sitophilus oryzae abstract This study reports the efficacy of using CO 2 against Sitophilus zeamais and Sitophilus oryzae as an alter- native treatment to fumigation for rice stored in a rice mill in Portugal. The trials were conducted in a silo containing 40 tonnes of polished rice and in four hermetic big bags of 1 tonne capacity; two with paddy and two with polished rice. The composition of the atmosphere ranged from 90 to 95% CO 2 and 0.7e2.1% O 2 . Three trials were carried out at different temperatures and treatment times; stored rice in the silo at 29.6  0.1  C for 26 days (first trial), at 34.1  0.2  C for 10 days (second trial), and in big bags at 22  C for 26 days (third trial). To evaluate the efficacy of each treatment, metal cages with 16 g of infested rice where placed at bottom, middle, top and surface of the polished rice in the silo. Four replications of each type of infested rice containing one-week-old S. zeamais adults, or eggs of S. zeamais or S. oryzae, were incubated in the laboratory, at the same temperature as in the silo, to serve as a control. In all modified atmosphere treatments adults of S. zeamais, and eggs of both S. oryzae and S. zeamais, showed mortality close to 100% and no F1 emergence was recorded in any treatment sample. This was the first time that a Portuguese rice mill used modified atmospheres. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Rice production is a seasonal crop in Europe. Portugal is the largest consumer of rice in Europe, and consequently around 2000 farmers and eight industries are associated with rice production, transportation and processing. Rice is stored as paddy in on-farm structures or in co-operatives in horizontal warehouses or vertical silos, until the end of winter when the remaining paddy is transported to processing facilities (Carvalho et al., 2004, 2010; Passarinho et al., 2008a,b). Among the pest species of stored paddy are Sitophilus oryzae (L.), Sitophilus zeamais Motschulsky and Rhy- zopertha dominica (F.) as the main weevils present in rice (Trematerra et al., 1999; Lucas and Riudavets, 2000; Pascual- Villalobos et al., 2006) in Portugal. The maize weevil S. zeamais, is the key-pest of stored rice, followed by S. oryzae (Carvalho et al., 2011). A common practice to control hidden infestation in stored paddy is the use of chemical fumigants to prevent insect develop- ment. The development of insect resistance to insecticides and consumer concern over the use of pesticides in food has resulted in the search for alternative methods of insect control. Consumers today expect a food product that is pesticide free or with much reduced residue levels. Modified atmospheres (MA) and controlled (CA) atmospheres have an important role in integrated pest management (IPM) systems that emphasise treatments without leaving pesticide resi- dues (Banks et al.,1991). Applications of MA technologies to preserve the quality and flavour of rice during storage are promising devel- opments (Navarro, 2006). They are safe and environmentally friendly tools for controlling insects and mites that affect a large number of raw and manufactured products and have been proposed as feasible alternative treatments since the Montreal Protocol phase- out of methyl bromide in 2005. Studies on high carbon dioxide (CO 2 ) MA have focused on the control of pests affecting raw or semi- processed food products in silos and warehouses as an alternative * Corresponding author. Tel.: þ351 21 361 72 47; fax: þ351 21 361 72 48. E-mail addresses: motiliac@netcabo.pt, motiliac@iict.pt (M.O. Carvalho). Contents lists available at SciVerse ScienceDirect Journal of Stored Products Research journal homepage: www.elsevier.com/locate/jspr 0022-474X/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.jspr.2012.05.001 Journal of Stored Products Research 50 (2012) 49e56