Enhancing insecticide activity using a physical mixture with cyclodextrin: a witch's cauldron or an opportunity?

Cyclodextrins have many advantages when used in the agricultural field as complexes with agrochemicals. However, they interact with molecules and biological systems at different levels and an enhancement of agrochemical effectiveness even as a physical mixture cannot be ruled out. This was verified for the first time by a simple experimental system with mealworm larvae (Tenebrio molitor L.) as the pest, the inhibitor of chitin synthesis diflubenzuron as the insecticide, and beta-cyclodextrin as the adjuvant. Under laboratory conditions, mealworm mortality was recorded under the following three treatments: (i) neat diflubenzuron, (ii) diflubenzuron/beta-cyclodextrin physical mixture, and (iii) commercial formulation Dimilin WP25. The physical mixture with beta-cyclodextrin significantly increased the mortality by enhancing the effectiveness of diflubenzuron. A significant dose effect was also found. Considering the application protocol, this result may be more likely due to the bioavailability enhancement of diflubenzuron by beta-cyclodextrin. On the basis of the current knowledge and available literature, we assume that these results could be explained by the interactions between CDs and biological membranes and the associated increase in their permeability. The use of beta-cyclodextrin in physical mixtures with insecticides could be of interest in the development of more effective agrochemicals through simpler and less costly research processes.