Influência de compostos voláteis herbívoro-induzidos de cana-de-açúcar, no comportamento de busca do parasitoide cotasia flavipes camaron (hymenoptera:braconidae)

Abstract

Diatraea flavipennella (Lepidoptera: Crambidae), known as the sugarcane borer, represents one of the main entomological problems of this culture. Currently, its control is achieved by means of the massal releasing of females of the parasitoid Cotesia flavipes (Hymenoptera: Braconidae), which, using olfactive clues, locates D. flavipennella larvae and parasitize them. Upon emergence of the parasitoid, the larvae of the sugarcane borer die. The olfactive clues used by C. flavipes females are related to odours released by the complex plant-host. However, information related to this species regarding the parasitoid searching behavior involving susceptible and resistant varieties of cane sugar plants and the nature of the Volatile Organic Compounds (VOCs) released by them is not available. Therefore, this project aims to investigate the influence of different varieties of sugarcane plants in the searching behavior of C. flavipes for larvae of D. flavipennella, considering the Volatile Organic Compounds (VOCs) released by: healthy sugarcane plants, sugarcane plants damaged by herbivory and induced resistant sugarcane plants. For that, larvae of D. flavipennella were reared using artificial diet and as soon as they reached the third instar, they were used in the experiments carried out in the Laboratório de Ecologia Química, Universidade Federal de Alagoas. Cocoons of C. flavipes and the varieties of sugarcane plants SP791011, RB92579 and RB867515 were provided by two sugarcane factories: Triunfo and Cachoeira do Meirim, state of Alagoas, Brazil. The Volatile Organic Compounds (VOCs) were collected by means of dynamic headspace from healthy plants, plants damaged by D. flavipenella larvae and induced resistant sugarcane plants treated with cis-jasmona under laboratory conditions. The obtained extracts were submitted to bioassays using a Y-shape olfactometer and C. flavipes females. For each treatment were used 10 replicates and on each bioassay 10 females of C. flavipes were used. Data from bioassays were submitted to the following non-parametric statistic tests: Kruskal-Wallis, Nemenyi e Mann-Whitney (p<0,05). The results demonstrated that C. flavipes females do not show any preference among the sugarcane varieties tested. However, they revealed that C. flavipes females are more attracted to plants damaged by D. flavipenella larvae and induced resistant sugarcane plants treated with cis-jasmona than healthy sugarcane plants. Chemical analyses of the sugar cane plant demonstrated quantitative and qualitative differences of the chemical composition and future identification will there concluded.