The fall armyworm, Spodoptera frugiperda (JE Smith) is a polyphagous pest of maize and horticultural crops in the Americas, but it recently was found in Africa as well. Main control strategies are based on the use of chemical insecticides or transgenic crops expressing Bacillus thuringiensis (Bt) toxins. However, in the last years, resistance of S. frugiperda field populations to Bt corn transgenic was detected in different Latin American countries. The available genomic information of S.

more »

... erda allows the development of new control technologies based on the use of RNA interference (RNAi). Three different S. frugiperda target genes were amplified and cloned to perform in vivo synthesis of specific dsRNA (ribosomal, trehalase and tubulin genes). Second to fourth larval instars were either fed, injected or soaked in dsRNA solutions and the effect on the target gene transcripts was evaluated by reverse transcriptase quantitative PCR (RT-qPCR). Only soaking second-instar larvae in dsRNA solution of ribosomal RNA gene sequence showed a statistically significant knockdown of target mRNA levels compared to control treatment. In contrast, no significant differences were registered on third and fourth larval stages. Therefore, the results showed that RNAi responses by soaking method depend of life stages, the method of inoculation and target gene sequence. Further research is needed in order to evaluate the use dsRNA as sprayable pesticide in fall armyworm strategies.