RNA control doubles mortality of Frankliniella occidentalis

Experiment revealed promising strategy for population control of Frankliniella occidentalis (thrips). Through oral delivery of double-stranded RNA (dsRNA) capable of silencing the gene for the enzyme trehalose-6-phosphate synthase (TPS), the insect suffered a drastic reduction in fecundity and an increase in mortality, with a population impact of 97% in just 100 days.

Frankliniella occidentalis attacks field and greenhouse crops, damaging plant tissue and transmitting phytopathogenic viruses. Since the 1960s, it has spread rapidly to at least 57 countries. Resistance to insecticides and the elimination of natural predators have made its control difficult.

The study evaluated the potential of RNA interference (RNAi) as an alternative. The target was the TPS gene, essential for the production of trehalose, a sugar vital for the metabolism, development and reproduction of insects. When they ingested the dsRNA synthesized in the laboratory or produced by modified bacteria (Escherichia coli), thrips showed a strong decrease in enzyme expression.

The effects were observed at different stages of the life cycle. In the first three days after dsRNA consumption, nymph mortality increased up to 5,5 times compared to the control group. Adults survived for less time and laid fewer eggs. The duration of the pre-reproductive period was extended. Life expectancy was reduced from 52,7 to 29,9 days. Fecundity fell from 209 to 54 eggs per female.

The analyses used stage-based life tables and population growth simulations. Within 100 days, the population that ingested dsTPS bacteria had reached 166 individuals—compared to 5,7 million in the control groups. That’s a decline of 1 in 34. The intrinsic growth rate and net reproduction rate also fell substantially.

This result is comparable to the efficacy of commercial insecticides. Furthermore, since the trehalose metabolic pathway does not occur in vertebrates, the method presents high specificity and low environmental risk.

The technique used two approaches: direct application of dsRNA in bean sprouts and use of E. coli modified to express the target gene. The second method proved to be more effective in the long term, even with partial degradation of the RNA by the insect's intestinal enzymes.

More information at doi.org/10.3390/insects16060614