BACKGROUND
The wettability of the target surfaces affects the wetting and deposition of pesticides on them. The properties of leaf surfaces change after infestation by Tetranychus urticae Koch. Studying the surface wettability of T. urticae and the changes in leaf wettability after infestation is important to guide the use of acaricides.
RESULTS
The body surface of T. urticae is an ellipsoidal crown covered with dense cuticle striations and hairs arranged in different directions, which makes the surface of T. urticae rough and hydrophobic. The abaxial surfaces of the leaves are rougher and more hydrophobic than the adaxial surfaces. After infestation by T. urticae, the faded spots were sunken on the adaxial surface and raised on the abaxial surface, where they had formed new wide peaks and valleys. The adaxial surface became obviously rougher and more hydrophobic, while the roughness of the abaxial surface became slightly larger, and the change in hydrophobicity was not obvious. The contact angles of the studied commercial acaricide on these surfaces were greater than 65° and were affected by the infestation. Reducing the surface tension can allow for better wetting of these surfaces and eliminate changes in leaf wettability.
CONCLUSION
The surfaces of kidney bean leaves became more hydrophobic after infestation by T. urticae with hydrophobic surface. The wettability of the acaricide solution should be adjusted according to the changes in leaf wettability. This study has important theoretical guiding significance for improving effective deposition of acaricide.
Nanopesticides have great impetus for enhancing the efficacy and safety of pesticides. Developing a simple and effective preparation method and controlling nanoparticle size growth during nanopesticides storage are still great challenges. In this paper, a new strategy was adopted to successfully construct nanodispersions. That is, pesticide was stored as soluble concentrate (SL), and the nanodispersion was formed by diluting with water when use. As an example, bifenazate-spirodiclofen (BS) complex SL was prepared and stable at 0 ± 2 and 54 °C ± 2 °C during 14-day storage. The mean particle size of the BS nanodispersion was less than 220 nm after standing for 24 h. The wettability and acaricidal activity of the BS nanodispersion were better than that of commercial SC. The universality of the strategy was also validated by bifenazate, spirodiclofen, abamectin, and difenoconazole. The strategy to construct a stable pesticide nanodispersion is simple, effective, and energy-efficient, which will promote the development of nanopesticides.
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