The Fall Armyworm (FAW), Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae), is one of the most important pests in the American continent and has recently become an invasive species in Africa. It’s main form of control is through the use of insecticides, however during the last 40 years, due to continuous spraying and high doses used along with FAW’s high adaptative capacity, developed resistance to different classes of chemical insecticides. One of the main mechanisms enabling resistance in the FAW is by detoxification enzymes or so-called metabolic resistance. P450s, Carboxylesterases and Glutathione-S-Transferases are the main families of enzymes believed to mediate the detoxification process. These enzymes in the FAW, although widely studied, have been difficult to generalize into patterns. This happens mainly because FAW populations can have high genetic variability within the species, as they have different biotypes meaning that they can be morphologically identical but physiologically different and consequently, enzymatic responses to toxic compounds can also differ. There are also differences due to the diversity of biomes in which S. frugiperda is found, which due to adaptations to different host plants and other abiotic factors, it’s hard to predict enzymatic responses in insecticide resistance. In this context we aimed to review the literature regarding these three main enzymes families involved in metabolic resistance in S. frugiperda, by cataloguing, analysing and summarizing these studies.

This work evaluated the biology and life table parameters of susceptible populations (Sus) of Spodoptera frugiperda to insecticides and Bt proteins, in conventional maize, Bt YieldGard VT PRO™ (Cry1A. 105/Cry2Ab) and PowerCore™ (Cry1A.105/Cry2Ab/Cry1F), millet and sorghum to better feeding behavior in this population. The following parameters were assessed: width of the cephalic capsule, duration and viability of larval, pupal and egg stages, pupal weight, sex ratio, adult longevity, pre-oviposition and oviposition period and daily fecundity The larval diet affected most of the parameters analyzed, with the exception of adult longevity and the period of embryonic development. The sus population completed its development in all hosts except in the VT PRO™ and PowerCore™ technologies. Non-Bt maize (87.50%) had higher larval viability, with larvae pupating nearly twice as fast (14,364 days) than sorghum (22,663 days) and millet (25,153 days), with the lowest viability (25.63%) and longest larval stage observed in millet. The pre-oviposition period was significantly shorter in maize (2.2 days) and longer in millet (6.5 days). Females fed on maize (1872.3) also showed higher total fertility than sorghum (671.0) and millet (405.0). Our results suggest that millet is the least suitable host for the development of this population. Although maize is considered the preferred host, S. frugiperda was able to complete its development in most of the tested hosts, indicating that sorghum and millet, plants commonly cultivated in the main producing regions of Brazil, can sustain susceptible populations in the field, although not as productively as maize and can act as a reservoir for the pest between seasons.

Spodoptera frugiperda is one of the most harmful pest threatening crops in tropical regions. It is particularly difficult to control due to its high polyphagia, mobility and the evolution of resistance. One of the main strategies enabling this insect to extend its geographic range, is the expression of a wide repertoire of detoxification enzymes, that neutralizes diverse environmental xenobiotics as well as insecticides. Hence adaptation to particular ecological niches can lead to different enzyme expression which consequently may affect its control. Even though the molecular basis of adaption is well known, there is not much applied studies regarding the effect of the geographic region in S. frugiperda physiology and management. Thus, the objective of this work was to determine the activity of detoxification enzymes, as well as the susceptibility to insecticides of S. frugiperda from distinct geographic origins in local hosts plants. Larvae from Pelotas, a region characterized by crop succession with oats and maize and larvae from Cascavel, which is characterized by highly intensive maize systems thought the year were used in the experiments. Our study showed that only larvae from Pelotas had increased enzyme activity after feeding on oat plants. In most insecticide treatments, mortality increased on population Cascavel after feeding on oats, the same was not observed on larvae from Pelotas. Our results are in accordance with previous studies that pointed distinct geographic conditions could lead to genetic variability and different responses to control. Information on S. frugiperda dynamics is essential to develop local management programs as well to better understand the complex nature of plant-insect interactions.