Monitoramento da resistência de populações de traça-do-tomateiro, Tuta absoluta (Meyrick, 1917), a metoxifenozida

Abstract

Brazil is currently the ninth largest tomato producer with approximately 4.3 million tons of fruit produced. The tomato crop presents several phytosanitary problems, among which is the occurrence of pest insects. Due to the severity of its damages, Tuta absoluta can be considered one of the main pests that affect the tomato crop and large outbreaks can lead to total loss of production of this crop. Although academic research contributes to control alternatives in integrated pest management, the main method used is chemical control. However, the continued use of insecticides is undesirable due to several aspects and the development of resistant populations. For this reason, monitoring studies should be carried out constantly to assist in the management of populations that present this phenotype in order to minimize possible damages. The objective of this work was to monitor T. absoluta populations with insect growth inhibitors (IGRs). The bioassays were conducted using the dose recommended by the manufacturer of the product methoxyfenozide (120 mg a.i./L) and a diagnostic dose of the same product for identification of the sensitive populations (10 mg a.i./L). After obtaining the results, the populations that obtained more distinct responses were submitted to concentration-response assays using eight concentrations to obtain the LC50. Among the 19 populations tested, only eight (GML, MGM, MGMSEL, SUM, GML2SEL, IRA, IRANO, AMD + PES) presented mortality above 80%. With regard to diagnostic dose, only five populations presented mortality above 80% (GML, MGM, MGMSEL, IRA, AMD + PES). The Gameleira population was used as a reference for susceptibility to methoxyfenozide. The LC50 obtained by concentration-response bioassays were 0.51 and 282.14 mg a.i./L for the populations of Gameleira and Guaraciaba, respectively. The resistance ratio between the two tested populations was 551.90 times. The probability of cross-resistance with the insecticide tebufenozide was tested and the LC50 obtained were 35.67 and 348.19 mg a.i./L for the populations of Gameleira and Guaraciaba, respectively. The resistance ratio for these populations to tebufenozide was 681.08. Thus, we can conclude a probable cross-resistance between methoxyfenozide and tebufenozide and the use of these products should be discontinued in these regions.