Encapsulating nootkatone to improve control of Ixodes scapularis

Plant phytotoxicity and short residual activity are two problems that may limit the potential to use nootkatone, an essential oil derived from citrus, as a natural acaricide to control the black-legged tick, Ixodes scapularis Say. We prepared two formulations (Maillard and Lignin) that encapsulated nootkatone oil and compared these formulations with the previously reported emulsifiable oil formulation (25% ai nootkatone) for plant phytotoxicity, nootkatone volatility under laboratory conditions, and toxicity to I. scapularis nymphs. The Maillard reaction between casein (25 g) and dextrin (50 g) was prepared and used to emulsify 50% w/w oil (485 mL total volume), which was spray dried to form a powder expected to contain 25% ai nootkatone. Ingredients for the Lignin encapsulation included nootkatone oil (60 g), surfactant (12 g), lignin (60 g), and calcium chloride (8.8 g) in an aqueous mixture (1120 ml total volume) that was spray dried to form a powder expected to contain 21% ai nootkatone. Encapsulated formulations caused less damage to treated cabbage leaves for application rates below 1 g/m2 when compared with the emusifiable formulation. Under controlled laboratory conditions, Maillard and Lignin encapsulated formulations reduced volatility of nootkatone by 2× and 4×, respectively, when compared with the emusifiable formulation. Encapsulation of the nootkatone oil did not alter toxicity when comparing among the formulations using a treated vial assay against I. scapularis nymphs.