Botanical oils as eco-friendly alternatives for controlling the rice weevil Sitophilus oryzae

Abstract

The rice weevil Sitophilus oryzae is a major stored grain pest infesting many grains in storage mainly wheat, rice and maize. Toxic effects of certain extracted botanical essential oils (EOs) were evaluated against the adults of Sitophilus oryzae (Linnaeus) (Coleoptera: Curculionidae). Bioassays were carried out by fumigation and guide tables were presented to show the effective range of concentrations of each of the evaluated essential oils and their corresponding mean number of responded insects. The essential oil of fennel (seeds) (Foeniculum vulgare) did not show any toxic effect up to the concentration of 300 µl/370 ml air and Common Sage (Marmaria leaves) (Salvia officinalis) up to 250 µl/370 ml air during the first 48 hrs then they showed a very weak effect. The essential oil of spearmint leaves (Mentha spicata L.) was the utmost toxic and had a lowest LC 50s calculated by 4.43, 3.88 and 3.27 µl/370 ml air after different exposure periods of 24, 48 and 72 hrs, respectively, followed by the essential oil of clove (Syzygium aromaticum) (382.62, 79.95 and 9.23 µl/370 ml air, in respect). In this concern, clove showed its higher toxicity after 72 hrs. The mortality of the exposed adults to EOs increased with the increase of concentrations and time of exposure to each one. The calculated values of toxicity index showed that the essential oil of mint was the most toxic EO (100%) followed by clove (35.43%). Moreover, log (dose)/N.E.D. (response) (Ld-p) regression lines for certain bio assayed botanical essential oils against S. oryzae were also illustrated. Therefore, it could be recommended that the essential oils of spearmint leaves and clove buds could be used to control the rice weevil, S. oryzae.

Toxicity evaluation of essential oil of clove (Syzygium aromaticum) bud against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

“…When exposure period is extended, mortality was increased which also lower the LC50 value. It is reported that clove oil showed its higher toxicity to S. oryzae only after 72 h (Saad et al 2017). Mishra et al (2012) evaluated the fumigation effect of clove oil against S. oryzae where LC50 of 17.32 and 15.34 μl were achieved at 24 and 48 h, respectively.…”

Chemistry and Insecticidal Activity of Essential Oils against Trogoderma granarium Larvae

“…These problems have stressed on the necessity for new alternatives with selective effects for the control of stored product insects. Among the available alternatives, plants-based products, such as essential oils, may offer a reliable tool for the management of stored product insects (Saad et al, 2017).…”