Nanocarrier-mediated transdermal delivery of Lmidgf4 dsRNA expedites biological control of locusts by Beauveria bassiana.

Locusts have been a major global agricultural pest that poses a serious threat to crop and livestock production. Entomopathogenic fungi (EPF) provide an eco-friendly control method; however, their efficacy usually takes slow and is unstable. To achieve an enhancement of the biocontrol efficacy of Beauveria bassiana (B. bassiana) against locusts, we developed a new strategy by which B. bassiana and nanocarrier-mediated dsRNA are co-applied across the locust cuticle. The nanocarrier star polycation (SPc) effectively delivers Lmidgf4 dsRNA (dsLmidgf4) into the locust, which targets Locusta migratoria imaginal disc growth factor 4 (Lmidgf4). SPc protects dsLmidgf4 from degradation by the hemolymph and enables efficient gene silencing. Furthermore, SPc has no adverse effects on B. bassiana spore germination and growth. Lmidgf4 interference leads to a thinner layer of endocuticle, thus facilitates infection of B. bassiana, and finally reduces the median lethal time of locusts infected with B. bassiana. In conclusion, the combination of B. bassiana and dsRNA/SPc complex overcomes the slow action of fungi, providing a novel strategy for field control of locusts.