Avaliação do efeito sinérgico dos compostos voláteis de frutos de Annona squamosa com o feromônio sexual na atração de machos de Cerconota anonella (Lepidoptera: Depressaridae) e da atividade inseticida da casca de Genipa americana sobre machos e fêmeas desta espécie

Abstract

Cerconota anonella is one of the most serious pests in commercial plantations of anonaceae, such as custard apple and soursop. Studies on the chemical communication of this species are scarce, and there is no record of products officially registered with the Ministry of Agriculture, Livestock and Supply (MAPA) for the control of pests and diseases in custard apple and soursop. Thus, techniques that aim to capture the insect, through specific attractants based on volatile compounds that trigger behavioral changes in the receiving organism (semiochemicals), are important objects of scientific investigation. With the search for natural products, free from toxicity and effective in the control of pest insects, extracts, isolated from plants which present insecticidal activity, can also be used in pest control, and arouse great scientific interest. The present study aim to identify the volatile compounds released by custard apple, in the ripe stage, which trigger the attraction of virgin males of C. anonella and also to obtain formulations of synthetic compounds and their respective mixtures for laboratory bioassays. Subsequently, the mixtures of volatiles from the pinecone fruits were tested in combination with the pheromonal extract of C. anonela females. The volatile compounds that mediate the interaction between the males of C. anonella and custard apple were extracted using the aeration technique and analyzed by Gas Chromatography coupled to Electroantenography (GC-EAG) and Gas Chromatography coupled to Mass Spectrometry (GC-MS). Three compounds elicited antennal activity in males of this species: myrcene, β-ocimene and linalool. Four mixtures of these synthetic compounds, in two concentrations, M1 (myrcene/β-ocymene/linalool), M2 (myrcene/β-ocymene), M3 (myrcene/linalool) and M4 (β-ocimene/linalool), were formulated in a biopolymer and used in behavioral bioassays in laboratory in a glass arena with virgin males of C. anonella. All mixtures tested elicited attraction in males, however, only two treatments, M3 (1μL/mL) and M4 (10μL/mL), showed greater attractiveness, differing statistically from the control treatment. Subsequently, the mixtures of fruit volatiles were added separately to the pheromone dose (in a 1:1 proportion) to evaluate the synergistic effect of the pheromone with the fruit volatiles. It was found that there was a potentiation of the attractive response when the M1 and M4 mixtures were added to the pheromonal extract, showing a significant difference when compared to the attractiveness of the pheromonal extract alone. Finally, the insecticidal activity of the trunk bark extract of Genipa americana on males and females of C. anonella was evaluated. For this, the crude extract was prepared in Tris-HCl 50 mM, pH 8.0, from the plant stem bark and inserted into the diets of caterpillars and adult insects, and they were kept in contact with the diet for a period of time 7 days. Thus, the survival of insects was analyzed. For caterpillars, the G. americana extract did not show a satisfactory mortality rate. However, in the evaluation of adults, it was found that the extract, in the three concentrations tested, resulted in insect mortality, however, the extract at 25% generated a mortality rate of 70% in 3 days of observation. The results of this research are promising for the use of alternative methods for the control of C. anonella, known as the annonaceae fruit borer.