Effects of geraniol and citronellal compounds on biochemical and reproductive parameters of Spodoptera frugiperda (Lepidoptera: Noctuidae).
The essential oils of plants are composed of several volatile compounds, which may have different concentrations and may be determinant for their toxicity. Thus, in this work, sublethal and lethal effects of the compounds, geraniol and citronellal on the biochemical and reproductive parameters of Spodoptera frugiperda were investigated. For the geraniol compound the LD30 of 9.42 mg/g and LD50 of 13.65 mg/g was used, while for the citronellal LD30 of 0.06 mg/g and LD50 of 0.08 mg/g. Pure acetone was used in the control. Third instar caterpillars were treated topically in the prothoracic region by applying 1 µl of the respective compounds with a HamiltonTM 50 µl syringe. After 48 h the caterpillars were macerated in sodium phosphate buffer at a ratio of 4 caterpillars/5 ml of the buffer, the levels of total protein, total sugar, lipid and glycogen were measured. The daily posture was evaluated in order to determine the periods of preoviposition, oviposition, post-oviposition and egg quantity. The results showed a reduction in the concentration of proteins and sugars for both compounds and concentrations studied. There was no change in lipid concentration. Citronellal increased the concentration of glycogen for both concentrations. The oviposition period and the number of eggs were reduced. However, there was no difference for the pre-oviposition and post-oviposition periods. Thus, it is inferred that geraniol and citronellal compounds cause alterations in the biochemical parameters that reflect in the reproduction of S. frugiperda.