The relationship between the amount of insect-repelling phenolic compounds in pennywort tea and the number of infesting cigarette beetles in the tea bag during one-year storage

Cigarette beetle, Lasioderma serricorne (F.), is a common food-product pest widely found in homes. This paper investigated the relationship between the number of infesting cigarette beetles and the phenolic content of pennywort tea made from young and mature leaves during one-year storage. It was found that cigarette beetles started to appear in tea bags after six months of storage. More adults were found than larvae and pupae. In addition, the number of cigarette beetles infesting pennywort tea made from mature leaves was higher than when it was made from young leaves. The amount of phenolic compounds in pennywort tea was analyzed by Folin–Ciocalteau assay. The results of a regression analysis indicated that the number of adult cigarette beetles correlated negatively with the amount of phenolic compounds in pennywort tea made from young leaves – when the total phenolic content decreased, the number of infesting cigarette beetles increased (r² = 0.80). The number of larvae and pupae showed a weak negative correlation with the amount of phenolic compounds (r² = 0.40 and r² = 0.56, respectively). Similar correlations were found in pennywort tea made from mature leaves, but the number of infesting beetles was higher due to the lower phenolic content of the mature leaves.