Susceptibility of Tribolium castaneum to Laurus nobilis essential oil and assessment on semolina quality

Abstract

Cereal production has always been an important component of Tunisian agriculture. However, insect pests are considered as a serious biosecurity threat to Tunisian cereals’ production and industry. Several methods such as fumigation have been used in storage. However, their use is controverted due to human and environmental worries. The main objective of this study was to introduce an ecologically safe method for managing the rust–red flour beetle, Tribolium castaneum. The insecticidal activities of Laurus nobilis have been extensively investigated. Therefore, the L. nobilis leaf essential oil chemical composition, and its insecticidal activity against T. castaneum adults were evaluated. Thus, a preliminary screening tests were designed to assess fumigant toxicity of Laurus nobilis essential oil against T. castaneum adults and to determine median effective concentrations (LC50 value). A second experiment was aimed to test the impact of spaces occupation with semolina and the storage period on essential oil effectiveness. T. castaneum adults were treated with the LC50 concentration and mortalities were assessed after 30, and 60 days of storage under 50% and 100% spaces occupied with semolina. Furthermore, the qualitative contamination of semolina by T. castaneum and the effect of essential oil on semolina characteristics and rheological dough properties were elucidated. Results indicated that the oil exhibited strong fumigant potentialities that depend on the exposure period and percentage of space occupation. The LT50 values for T. castaneum ranged from 70.48 h for 50% space occupation with semolina to 43.44 h for 100% space occupation with semolina. Moreover, we investigated the essential oil impact on semolina characteristics (protein, ash, gluten, and moisture) and rheological dough. Results indicated that the oil exhibited strong fumigant potentialities that depend on the exposure period and percentage of space occupation. It was also revealed that essential oil treatment slightly modified semolina characteristics but did not affect rheological properties that still conformed with ISO standards. The results of this study can be interested in further phytochemical and insecticidal activities of L. nobilis essential oil as alternative fumigants for control of stored semolina without negative effect on the quality of semolina.