Determinación de parámetros de desarrollo en estados inmaduros de Spodoptera cosmioides (Walker) criadas en dos sustratos diferentes: Determination of developmental parameters of immature stages of Spodoptera cosmioides (Walker) reared on two different substrates

The use of Bt soybean resulted in an important advance in the control of pests that affect this crop. However, in recent years there has been an increase in damage caused by lepidopteran species not targeted by this technology; among them Spodoptera cosmioides (Walker). This work analyzed the development of immature stages of S. cosmioides reared on two different substrates: Amaranthus spp. and Bt soybean. Newly hatched larvae of the F1 obtained from collections in commercial fields of Bt soybean in the province of Tucuman, Argentina were used. For each substrate, 100 larvae were reared individually throughout their development. The occurrence of molts was recorded daily and the cephalic capsules were kept for measurement. Once the pupal stage was completed, pupae were weighed and the sex was determined. With the number of adults obtained, the viability of the pupal stage was determined. The duration of the larval stadiums presented statistically significant differences for the L2, L6 and L7 stadiums. Overall, the length of the larval stage was slower in Bt soybean; which, in turn, featured additional stadiums. The width of the cephalic capsules showed statistically significant differences in L2 and L5. The pupae from larvae fed Bt soybean were lighter than those of Amaranthus spp. For the duration of the pupal stage the differences were not statistically significant. There were no statistically significant differences attributable to the substrate for the sex ratio and for the survival analysis (Kaplan-Meier). The results show that Bt soybean are a less appropriate substrate for the development of S. cosmioides than Amaranthus spp.