Important pest species of the Spodoptera complex: Biology, thermal requirements and ecological zoning

In South America, especially in Brazil, four members of the Spodoptera complex, Spodoptera albula (Walker, 1857), S. cosmioides (Walker, 1858), S. eridania (Stoll, 1782), and S. frugiperda (J.E. Smith, 1797) are important pests of many crops, in particular corn, soybean and cotton crops. Spodoptera eridania and S. frugiperda have recently invaded Africa and caused serious crop damage, and S. frugiperda has invaded Asia and Oceania. The present study tested the effect of a range of seven temperatures (18–34 °C) on these four Spodoptera species simultaneously, assessing several biological variables. Based on the thermal tolerances obtained experimentally, the ecological zoning of each species in Brazil was mapped and compared spatially, according to the crop calendar of three important crops in different regions (first and second corn harvest, soybean and cotton). Our results showed that S. eridania had the lowest temperature threshold (Tt), i.e., it is favored in regions with more moderate temperatures; and did not tolerate the warmest temperature, failing to complete its development at 34 °C. In contrast, S. albula did not complete its development at 18 °C and may be more successful in warmer regions. In general, S. frugiperda and S. cosmioides were able to develop over a wide range of temperatures, and S. frugiperda showed a higher biological potential at all temperatures evaluated. Our biological data and the computational code are available online. The extensive data produced here can help other entomologists to delimit the spatial distribution of the Spodoptera complex and forecast outbreaks of these pests.