Mass rearing requirements and ecological zoning of Telenomus remus estimated through life table in different temperatures and relative humidities

Abstract

Spodoptera frugiperda (J.E. Smith) is an important polyphagous pest of corn (maize) crops, reported as invasive on most continents. It is the main corn pest in South America. Control methods involve the use of agrochemicals and genetically modified cultivars. Among the possible alternatives for controlling this species, the present study evaluated the biological development of an isofemale line of Telenomus remus Nixon collected in Piracicaba, São Paulo, Brazil, on eggs of S. frugiperda at different temperatures and relative humidity (RH) levels. The development and parasitism of the parental generation of T. remus and its offspring were evaluated at different temperatures (18, 20, 22, 25, 28, 30, 33, and 35 °C) and RH levels (30, 50, 70, and 90 %). Fertility life tables were constructed based on the values obtained at different temperatures and RH. The estimated thermal constant (K) was 210.36 degree-days, the lower temperature threshold (Tt) 10.6 °C, and the upper developmental threshold (Tmax) 35.9 °C. In both generations, T. remus showed the best parasitism performance at temperatures between 25 and 30 °C and RH between 50 and 70 %. We represented the results geographically, producing two types of zoning maps, one based on R₀ (net reproductive rate) values and another based on the number of T. remus generations in municipalities according to the calendar for the first and second corn crops. Both zoning approaches indicated that the North, Northeast, Midwest, and Southeast regions of Brazil are the most suitable for the establishment and multiplication of T. remus, especially from September to February. In the colder Southern region, conditions are suitable only from November to March. Under the same climate conditions as S. frugiperda, T. remus can produce 4 to 6 times more generations in both corn crops. For the first corn crop, more regions of Brazil are favorable for the release of T. remus to control S. frugiperda.