Control of two sucking insect pests, a whitefly (Bemisia tabaci) and a thrips (Frankliniella occidentalis), infesting hot peppers by spraying LDH-formulated dsRNA.

BACKGROUND

Whiteflies and thrips are serious pests by feeding on plant tissues and transmitting plant viruses to crops. To avoid excessive uses of chemical insecticides, spraying double-stranded RNA (dsRNA) has been proposed as an alternative control measure against these sucking insect pests. However, it is not clear how best to effectively deliver dsRNA to the sucking insects.

RESULTS

A potent dsRNA was generated against a vacuolar type ATPase subunit B (vATPase-B) gene of the silverleaf whitefly, Bemisia tabaci, which shares a high sequence homology (85.7%) with that of the western flower thrips, Frankliniella occidentalis. The gene was well expressed in the intestine of the whitefly at the nymph and adult stages, in which it was highly expressed at the filter chamber and midgut areas from a fluorescence in situ hybridization analysis. Due to its sucking feeding behavior, it was considered impossible to deliver the sprayed dsRNA to the internal body of the sucking insects. This study showed the difference between the two insects, in which the thrips could uptake the sprayed dsRNA and underwent high mortality while the whiteflies could not. To explain the low mortality due to the inefficient dsRNA delivery in B. tabaci, the dsRNA was expressed in the host plant by virus-induced gene silencing (VIGS). As expected, dsRNA expressed in the VIGS-treated plant hosts was well delivered to the intestine of B. tabaci as well as F. occidentalis and killed both sucking insects. To facilitate the dsRNA delivery to the plant tissues, two dsRNA formulations were compared in the control efficacy of the sucking insects. Compared to unformulated dsRNA, either chitosan- or layered double hydroxide (LDH)-formulation was effective to enhance the control efficacy against both sucking insects. Furthermore, LDH formulation was much more effective to control B. tabaci. When LDH-formulated dsRNA was sprayed to hot peppers infested by whiteflies and thrips, it resulted in over 80% control efficacy against the whiteflies and the thrips. These control efficacies were similar to those of a chemical insecticide, Spinosad. In addition, compared to the unformulated dsRNA, the LDH-formulated dsRNA exhibited a relatively long residual control efficacy, which may reduce the spraying amount of the dsRNA insecticide.

CONCLUSION

These results suggest that LDH formulation is useful for dsRNA delivery against the two sucking insects. The LDH-dsRNA specific to vATPase-B of B. tabaci was effective to control both whitefly and thrips infesting hot peppers. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.