α-Terpineol: An Aggregation Pheromone in Optatus palmaris (Coleoptera: Curculionidae) (Pascoe, 1889) Enhanced by Its Host-Plant Volatiles

Abstract

The Annonaceae fruits weevil (Optatus palmaris) causes high losses to the soursop production in Mexico. Damage occurs when larvae and adults feed on the fruits; however, there is limited research about control strategies against this pest. However, pheromones provide a high potential management scheme for this curculio. Thus, this research characterized the behavior and volatile production of O. palmaris in response to their feeding habits. Olfactometry assays established preference by weevils to volatiles produced by feeding males and soursop. The behavior observed suggests the presence of an aggregation pheromone and a kairomone. Subsequently, insect volatiles sampled by solid-phase microextraction and dynamic headspace detected a unique compound on feeding males increased especially when feeding. Feeding-starvation experiments showed an averaged fifteen-fold increase in the concentration of a monoterpenoid on males feeding on soursop, and a decrease of the release of this compound males stop feeding. GC-MS analysis of volatiles identified this compound as α-terpineol. Further olfactometry assays using α-terpineol and soursop, demonstrated that this combination is double attractive to Annonaceae weevils than only soursop volatiles. The results showed a complementation effect between α-terpineol and soursop volatiles. Thus, α-terpineol is the aggregation pheromone of O. palmaris, and its concentration is enhanced by host-plant volatiles.

Volatilome Analysis of Soursop Fruits for the Determination of Kairomone Components That Attract the Annonaceae Fruit Weevil (Optatus palmaris Pascoe)

“…Moreover, the comparison of the attraction values of the binary and tertiary mixtures showed that the tertiary mixture was significantly more attractive to male and female weevils than the binary mixture (t < 0.05). Also, the preference percentages obtained from the tertiary mixture were comparable to those obtained from soursop slices supplemented with α-terpineol and males feeding on soursop fruits [15]. Nevertheless, it is important to conduct more laboratory and field experiments, with larger insect groups, to determine a final attractant product for Annonaceae fruit weevils.…”

“…For instance, in a previous study, the role of α-terpineol as an aggregation pheromone was proven in the management of this Annonaceae fruit weevil. Moreover, in the same study, the whole bouquet of soursop volatiles was demonstrated to enhance the attraction effects of α-terpineol to this curculio [15]. Nevertheless, specific volatile compounds in the aroma of soursop were not identified or correlated with the attraction effects over these weevils.…”

“…The peak areas obtained from the calibration curves were normalized to the area of the internal standard. The matrix extraction effect experiments for volatile content estimations were performed as previously described [15]. The recovering correction for benzothiazole and (E)-β-caryophyllene was 63 and 64%, respectively.…”

“…The olfactometry assays consisted of two-choice experiments that were individually performed for male and female specimens. The setting up of the olfactometer and the use of insects in the bioassays were performed as previously reported for this pest [15]. Briefly, the experimental room was black-matte colored to avoid light reflections.…”

A Theme Issue to Celebrate Professor Robert Verpoorte’s 75th Birthday: “The Past, Current, and Future of Natural Products”

“…Alongside these main streams of natural products research, two multidisciplinary investigations were reported: a study on natural products formulation with ionic liquids that are known as promising green media, Kiyonga et al [ 15 ] and a chemical ecology study related to pheromones by Pineda-Rios [ 16 ].…”