Individual and combined effects of Juniperus phoenicea and J. oxycedrus powders on insecticidal activity against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae)

Abstract

Tribolium castaneum (Herbst) and Rhyzopertha dominica (Fabricius) are two major beetle pests that affect the quality and commercial value of stored products. The aim of this study is to evaluate the insecticidal effect of Juniperus phoenicea and Juniperus oxycedrus, as well as their binary combinations, against adults of T. castaneum and R. dominica. Masses of 1, 1.5, 2, 2.5, and 3 g were used for each plant powder as well as for their binary combination (75% of J. phoenicea powder and 25% of J. oxycedrus). The results obtained revealed that the two powders tested separately revealed a notable effectiveness against T. castaneum and R. dominica. In particular, J. phoenicea is the most toxic against T. castaneum (LD₅₀ = 0.52 g) after 240 h of exposure, and R. dominica (LD₅₀ = 0.60 g) after 192 h of exposure. In combination, the powders showed increased toxicity against T. castaneum (LD₅₀ = 0.55 g) and R. dominica (LD₅₀ = 0.42 g) after 144 h of exposure. The potential of these powders may prove to be an effective and environmentally friendly method of preventing infestations of T. castaneum and R. dominica adults.