Cutworms (Lepidoptera: Noctuidae) in central Brazil Savanna: temporal distribution and association of species abundance with climatic and meteorological factors

Abstract

AbstractPopulation dynamics studies make it possible to predict the response of species to seasonal and inter‐annual climatic phenomena in hypothetical scenarios of climatic abnormality. However, long‐term studies on the temporal distribution and abundances of species are still scarce in the literature, including for species of agricultural importance. The present study aimed to bridge this gap through monthly collection events of species of cutworms (species of Agrotis and Feltia) across eight crop seasons (from July 2012 to June 2020) in the Brazilian Savanna (Cerrado). This biome is characterised by an irregular distribution of rainfall during a normal year, including two well‐defined periods of dry and rainy seasons. Only five species of cutworms were recorded: Agrotis ipsilon, Agrotis canities, Feltia repleta, Feltia submontana and Feltia subterranea, all widely distributed across South America. Except for F. submontana, occurring only in the autumn, other species occurred nearly year‐round, with distinct peaks of abundance in the dry season (April to October), supporting the hypothesis that species of Agrotina are well adapted to dry environments. The association of cutworms with dry environments was recovered for multivoltine, abundant species, such as A. ipsilon and F. subterranea, as for univoltine species, such as F. submontana. Across eight crop seasons, the abundance of all species decreased, coinciding with a high intensity El Niño effect. However, the effect itself was not found to be significant to predict the temporal distribution and abundances of cutworms and the causes of population decrease from 2014 to 2015 crop season remain to be explained. After the temporal autocorrelation effects were removed, it was revealed that the abundance of cutworms tends to be larger in crop seasons with less precipitation. Thus, this variable can be used to predict outbreaks of cutworms in the Cerrado. Some species of cutworms deserve special concern due to their frequency, seasonality and higher abundances in the Cerrado during the dry season. Their adaptability to adverse conditions may increase their spatio‐temporal distribution in Brazil and the frequency of outbreaks in a scenario of climate change, with the continuing reduction of rainfall in central and southeastern Brazil.