Ecologia química, dimorfismo sexual e observação de danos de Ozopherus muricatus Pascoe, 1872 ( Coleoptera: Curculionidae)

Abstract

The coleopteran Ozopherus muricatus Pascoe, 1872 (Coleoptera: Curculionidae) is an insect coming from the Amazon region, little known, and which now has economic importance as it has become a pest of açai palm, Euterpe oleracea Mart. (Family: Arecaceae) mainly in the state of Rondônia. Female burrow holes on the basis of the cluster in order to oviposit, the larvae then blocks the inside of the cluster preventing the fruits from developing. The main objective of this study is to investigate the chemical ecology, field behavior of this insect and to characterize the sexual dimorphism in order to explore new aspects in which to control the pest. Field observations were conducted in acai plantations located in Rondonia. Sexual dimorphism studies were conducted with a sample size of 50 females and males, and 20 pupes, using a stereoscopic microscope. Volatiles were collected from separately from female and males throughout 48 hours using air entrainment. Air entrainment was also used to collect volatiles from different parts of the host plant (cluster with flower, cluster with immature fruits, cluster with mature fruits, and pieces of clusters), air entrainment was conducted for 48 hours for all the different parts except for the pieces of cluster which was conducted for 8 hours. Sample analysis was conducted using gas-chromatography (GC), and coupled gas-chromatography with mass-spectrometry (GC-MS). Each volatile sample was tested in behavioral assays using a Y-tube olfactometer. Electrophysiological tests were conducted using coupled gas-chromatography with electroantennogram, using all the volatile samples that elicited a significant difference in the behavioral assays. It was determined that the larvae block the path inside the cluster thus inhibiting the passage of SAP resulting in lack of fruit production. Dimorphism in O.muricatus pupes showed that females present two protuberances in the terminal and ventral region of the abdomen, which is absent in males. In adults the difference was observed in the final abdominal tergites; the seventh and eighth tergite of the males are visible, whilst in females the eighth tergite covers the seventh one completely. In the behavioral assays, females showed a significant attraction to the four host plant samples, whilst males only presented a significant attraction to the cluster with flower, and pieces of cluster samples. When testing the attraction of females to males and vice-versa, a significant attraction was confirmed suggesting the possible release of aggregation pheromone. A total of fourteen electrophysiological responses were observed when testing the extracts of cluster with flower, cluster pieces, males and females. Twelve of these responses were identified using GC-MS: Benzyl alcohol, cis-Linalool oxide, 2,2,6-trimethyl-3-keto-6-vinyltetrahydropyran, cis-Linalool oxide (furanoidic form), Linalool oxide cis (furanoidic form), α-neo-iso-menthol, Undecane, 2,9-dimethyl, Cuparene, p-Ethylanisole, Decane, 2,3,5-trimethyl, Decane, 2,3,5-trimethyl (Farnesane), 1-Hexadecanol, 3,7,11,15-tetramethyl.