Sublethal Exposure to Clove and Cinnamon Essential Oils Induces Hormetic-Like Responses and Disturbs Behavioral and Respiratory Responses inSitophilus zeamais(Coleoptera: Curculionidae)

Abstract

Essential oils have been suggested as suitable alternatives for controlling insect pests. However, the potential adaptive responses elicited in insects for mitigating the actions of these compounds have not received adequate attention. Furthermore, as is widely reported with traditional insecticides, sublethal exposure to essential oils might induce stimulatory responses or contribute to the development of resistance strategies that can compromise the management of insect pests. The current study evaluated the locomotory and respiratory responses as well as the number of larvae per grain produced by the maize weevil, Sitophilus zeamais Motschulsky, after being sublethally exposed to the essential oils of clove, Syzygium aromaticum L., and cinnamon, Cinnamomum zeylanicum L. The essential oils showed similar insecticidal toxicity (exposure route: contact with dried residues; Clove LC95 = 3.96 [2.78-6.75] µl/cm(2); Cinnamon LC95 = 3.47 [2.75-4.73] µl/cm(2)). A stimulatory effect on the median survival time (TL50) was observed when insects were exposed to low concentrations of each oil. Moreover, a higher number of larvae per grain was produced under sublethal exposure to clove essential oil. S. zeamais avoided the treated areas (in free-choice experiments) and altered their mobility when sublethally exposed to both essential oils. The respiratory rates of S. zeamais (i.e., CO2 production) were significantly reduced under low concentrations of the essential oils. We recommend the consideration of the potential sublethal effects elicited by botanical pesticides during the development of integrated pest management programs aiming to control S. zeamais.

In Vitro-In Vivo Dose Response of Ursolic Acid, Sulforaphane, PEITC, and Curcumin in Cancer Prevention

“…It was suggested the biphasic dose-response is through a homeostasis mechanism, in which a low dose of agents stimulates signaling pathways to protect the organism, whereas a high dose displays an inhibitory effect (145) (146). A similar phenomenon has been observed for many natural compounds, such as resveratrol (147) (22), berberine (148), clove and cinnamon essential oils (149). …”

Toxic and hormetic-like effects of three components of citrus essential oils on adult Mediterranean fruit flies (Ceratitis capitata)

“…Low amount of sweet orange EO had a stimulatory effect by increasing fecundity and decreasing preoviposition periods while the opposite was observed with high doses of sweet orange EO. Hormetic-like effects of phytochemicals and insecticides have been recorded as increased fecundity in other insect species, as well [5, 30, 34]. Azadirachtin sub-lethal doses increase the fecundity of Zabrotes subfasciatus (Boheman) (Chrysomelidae: Bruchinae) and decrease the survival [34], possibly indicating a trade-off between longevity and reproduction in stressful environments that is induced by either an increase of juvenile hormone levels [35] or a shift in resource allocation [36].…”

“…These may include stimulatory, deterrent, toxic and even hormetic effects [2–5]. Essential oils (EOs) and other secondary metabolites constitute components of the plant defensive mechanisms and strong drivers of evolutionary events inducing selection pressures to herbivores [6].…”

The Sublethal Effects of Insecticides in Insects

“…Sublethal doses of methomyl promoted behavioral disruption of S. littoralis for food odors [27]. Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) exposed to Cinnamomum zeylanicum L. (Lauraceae) had their locomotor behavior affected, such as time, speed and distance of walk [28].…”