The effectiveness of clove oil, its fractions, and clove oil-based fumigant tablet formulations, against Tribolium castaneum (Herbst)

Indonesia has seen an increase and widespread reports of resistance among stored-product insect pests to phosphine. The use of Syzigium aromaticum (clove oil) as an alternative fumigant may be a useful strategy to control infestation by phosphine-resistant varieties of stored-product insects. The objective of this study was to examine the effectiveness of whole (unfractionated) clove oil as well as its component fractions as a fumigant and repellent against the red flour beetle (Tribolium castaneum (Herbst)), and to develop a simple fumigant formulation for this purpose. The experimental design used to test the effectiveness of clove oil and its fractionation was a completely randomized design (CRD). Meanwhile, testing the effectiveness of tablet formulations was carried out by factorial CRD. Fumigation test results gave LD50 and LD95 values of 0.234 and 1.142 ml/l respectively, for crude clove oil used in a fumigation chamber against T. castaneum. An n-hexane fraction of clove oil tested under the same conditions was more lethal, causing 95% mortality of T. castaneum at the dose of 0.801 ml/l during fumigation. Finally, tablets containing a set proportion of clove oil and naphthalene (1:1) reached LD91 against T. castaneum after 7 days’ fumigation.

Repellent and Toxicant Effects of Eight Essential Oils against the Red Flour Beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

This study was conducted to compare the repellent effect and contact toxicity of eight essential oils (EOs), including Syzygium aromaticum, Allium sativum, Eucalyptus camaldulensis, Lavandula officinalis, Simmondsia chinensis, Matricaria chamomilla, Citrus limon, and Prunus dulcis, against adults of Tribolium castaneum Herbst. Four concentrations (1, 5, 10, and 15% in acetone solvent) of each EO were tested. The 5, 10, and 15% concentrations of S. aromaticum EO had a high repellency effect against T. castaneum compared with A. sativum, E. camaldulensis, L. officinalis, S. chinensis, M. chamomilla, C. limon, and P. dulcis after 30 min of exposure. The repellency test of the S. aromaticum, E. camaldulensis, L. officinalis, M. chamomilla, C. limon, and P. dulcis EOs on T. castaneum has shown that the mortality percentages enhanced with the increase in the EOs concentration and also with the exposure time. The 15% concentration of P. dulcis and M. chamomilla EOs have a significant impact on the mortality rate of T. castaneum compared with S. aromaticum, A. sativum, E. camaldulensis, L. officinalis, and S. chinensis after the 24 h of contact test. Moreover, the 15% concentration of the C. limon EO caused a greater mortality percentage compared with S. aromaticum, A. sativum, E. camaldulensis, and L. officinalis. It could be concluded that using the S. aromaticum EO as a repellent oil and using P. dulcis, M. chamomilla, and C. limon for contact toxicity to treat the flour infested by T. castaneum can play an important role in protecting stored grains and their products.

cDNA Cloning and Partial Characterization of the DJ-1 Gene from Tribolium castaneum

The DJ-1 gene is highly conserved across a wide variety of organisms and it plays a role in anti-oxidative stress mechanisms in cells. The red flour beetle, Tribolium castaneum, is widely used as a model insect species because it is easy to evaluate gene function in this species using RNA interference (RNAi). The T. castaneum DJ-1 (TcDJ-1) sequence is annotated in the T. castaneum genome database; however, the function and characteristics of the TcDJ-1 gene have not been elucidated. Here, we investigated the cDNA sequence of TcDJ-1 and partially characterized its function. First, we examined the TcDJ-1 amino acid sequence and found that it was highly conserved with sequences from other species. TcDJ-1 mRNA expression was higher in the early pupal and adult developmental stages. We evaluated oxidant tolerance in TcDJ-1 knockdown adults using paraquat and found that adults with TcDJ-1 knockdown exhibited increased sensitivity to paraquat. Our findings show that TcDJ-1 has an antioxidant function, as observed for DJ-1 from other insects. Therefore, these results suggest that TcDJ-1 protects against oxidative stress during metamorphosis.