Resistência de >i<Spodoptera frugiperda>/i< (Lepidoptera: Noctuidae) a inseticidas bloqueadores de canais de sódio

Abstract

Resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to sodium channel blocker insecticides Spodoptera frugiperda (Lepidoptera: Noctuidae) is the major maize pest in Brazil, and its control have been based on the use insecticides and transgenic plants expressing proteins of Bacillus thuringiensis Berliner (Bt). Several cases of S. frugiperda resistance to these control tactics have already been documented and resistance has been one of the major threats to integrated pest management (IPM) programs. Therefore, the use of insecticides with new modes of action such as sodium channel blockers (indoxacarb and metaflumizone) could help in insect resistance management programs (IRM). To develop an IRM program, the goals of this research were (i) To characterize the baseline susceptibility to indoxacarb and metaflumizone in S. frugiperda populations colletected from major maize-growing regions in Brazil; (ii) To monitor the S. frugiperda resistance to indoxacarb and metaflimizone in populations collected from 2017 to 2020 growing seasons; (iii) To evaluate the response to indoxacarb and metaflumizone in strains of S. frugiperda susceptible and resistant to some selected insecticides and Bt proteins; (iv) To select a resitant strain of S. frugiperda resistant to sodium channel blockers insecticides under laboratory coditions to characterize the genetic basis of resistance and cross-resistance between insecticides that act on sodium channels; and (v) To evaluate fitness costs associated with resistance of S. frugiperda to indoxacarb and metaflumizone. Low variation in susceptibility to indoxacarb (4.6-fold) and metaflumizone (2.6-fold) was detected in populations of S. frugiperda collected in 2017. The frequency of the resistance allele to indoxacarb was 0.0452 (0.0382 -0.0527 CI 95%), by using F2 screen method. The mean survival at diagnostic concentration, based on LC99, varied from 0.2 to 12.2% for indoxacarb and from 0.0 to 12.7% for metaflumizone in populations of S. frugiperda collected in Brazil from 2017 to 2020. The resistance ratio of S. frugiperda to indoxacarb was ≈ 30-fold and to metaflumizone was > 600-fold. No cross-resistance was detected between sodium channel blocker insecticides (indoxacarb and metaflumizone) and other insecticides (chlorpyrifos, lambda-cyhalothrin, lufenuron, teflubenzuron, spinetoram and chlorantraniliprole) and Bt proteins (Cry1A.105/Cry2Ab2/Cry1F and Vip3Aa20). On the other hand, cross-resistance between indoxacarb and metaflumizone was detected. The inheritance of resistance of S. frugiperda to indoxacarb and metaflumizone was autosomal, incompletely recessive and with polygenic effect. In addition, significant fitness costs associated with S. frugiperda resistance to indoxacarb and metaflumizone were observed in life history traits evaluated under laboratory conditions in the absence of selection pressure. Thus, based on information obtained in this study, indoxacarb and metaflumizone are important tools to be exploited in IRM programs in Brazil.