Fabrication of nanogels to improve the toxicity and persistence of cycloxaprid against Diaphorina citri, the vector of citrus huanglongbing.

Introduction: Diaphorina citri is the most serious pest of citrus worldwide because it is the natural insect vector of huanglongbing. Cycloxaprid (Cyc) was highly toxic to D. citri. However, the poor solubility and stability had limited its development.

Objectives: In order to improve the insecticidal effect and stability to harsh climatic conditions of Cyc.

Methods: Cyc was chosen as the representative pesticide, 4,4'-methylenebis (phenyl isocyanate), PEG-600 and n-butanol were used to prepare sustained-release nano-gelation particles (Cyc@NGs).

Results: Cyc@NGs enhance the toxicity of Cyc more than 3 folds. Furthermore, Cyc@NGs showed excellent anti-rain and anti-UV capacity. After being exposed to ultraviolet light for 12 h, Cyc decreased by 100 %, while the insecticide content of Cyc@NGs only decreased by 25 %. Additionally, Cyc@NGs possessed better wettability on citrus leaves, mainly benefitting from its lower contact angle on citrus leaves. Moreover, FITC-labeled nano-gelation particles (FITC-NGs) exhibited high capability to penetrate and enrich in citrus leaf tissue and D. citri midgut. Consequently, NGs promoted the translocation and durability of insecticides, thereby, increasing the insecticidal activity. The results suggested that nano-gelation particle is a promising platform to deliver insecticides and Cyc@NGs would be the suitable candidate for the effective management of D. citri.