Evaluation of a Lignin-Encapsulated Nootkatone Formulation AgainstTetranychus urticae(Acari: Tetranychidae)

Abstract

Botanical-based miticides, such as neem oil, are used in organic and conventional agronomic production as part of chemical rotation plans to suppress pest mite populations. Other plant-based compounds such as nootkatone (a component of essential oils distilled from grapefruit, Citrus paradisi Macfayden (Rutaceae), and Alaskan yellow cedar, Chamaecyparis nootkatensis [D. Don] Spach [Cupressaceae]), also may serve as effective organic miticides in crop production systems. We report on a lignin-encapsulated (LE) nootkatone formulation (previously effective at repelling ticks) that was evaluated as a miticide against the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). At an application rate of 1 g/L AI, LE nootkatone caused 85% mortality of spider mites in the absence of silk webbing, but only 12% mortality when webbing was present. Another component of Alaskan yellow cedar oil, carvacrol, was added at a rate of 1 ml/L to the LE formulation. Spider mite mortality to this formulation, with webbing present, increased to 81%. Although the LE nootkatone and carvacrol combination exhibited phytotoxicity, it does have potential as a miticide. However, more work is needed to reduce the phytotoxicity of current formulations.