Antisense DNA acaricide targeting pre-rRNA of two-spotted spider mite Tetranychus urticae as efficacy-enhancing agent of fungus Metarhizium robertsii

Two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most dangerous pests in the world and one of the most pesticide-resistant species ever. Complex biological preparations are of great interest for the acaricide market because they do not poison ecosystems and do not bioaccumulate in food products, simultaneously, pests more slowly develop resistance to complex preparations. In this study we applied complex bioformulation composed of 11-mer antisense oligonucleotide (oligonucleotide acaricide or DNA acaricide) Tur-3 and fungus Metarhizium robertsii for T. urticae control. We discovered that joint contact application of DNA acaricide and fungus M. robertsii significantly attenuates reproduction rate of the mite. Our results indicate that DNA acaricide Tur-3 and fungus M. robertsii act synergistically and lead to a significant 7-times elevated mortality rate and 5-times reduced fecundity of the mite. Oligonucleotide acaricide Tur-3 causes 2,5-fold re-duction of expression of the target pre-rRNA of T. urticae and suppresses the activity of key players of detoxifying enzymes of its defense system (phenoloxidase, esterase, glutathione-S-transferase), on average, by 2-3 times. Oligonucleotide acaricide Tur-3 interferes with protein biosynthesis causing decrease in production of defense system enzymes of the pest. Obviously, attenuation of defense system enhances fungal infection or/and fungus produces a variety of enzymes that degrade and destroy the integument structure of the pest, aiding the penetration of oligonucleotide acaricide Tur-3. This research article is the first evidence of successful application of oligonucleotide acaricide together with fungus M. robertsii for efficient T. urticae control. Combined application of oligonucleotide acaricides based on conservative antisense sequences of rDNA of pests and fungi is a potent and selective approach for eco-friendly plant protection.