Acaricidal properties of essential oils from agro-industrial waste products from citric fruit against Tetranychus urticae

Tetranychus urticae is a major agricultural pest with worldwide distribution that has caused considerable damage to vegetable crops in north-eastern Brazil. The aim of the present study was to investigate the chemical and lethal/sublethal effects of essential oils from the peels of the lime (Citrus aurantiifolia), lemon (C. limon), mandarin orange (C. reticulata) and (C. reticulata x C. sinensis) as well as selected constituents (linalool, alpha-terpineol, alpha-pinene, beta-pinene, terpinolene and limonene) against T. urticae. The greatest yield was achieved with the mandarin and tangerine peel oils. The chemical analysis (gas chromatography-mass spectrometry) of the essential oils from the Citrus fruit peels enabled the identification of 127 compounds, revealing a predominance of monoterpenes. Limonene was the major constituent, and alpha-pinene, beta-pinene, linalool and alpha-terpineol were found in substantial quantities. Regarding the susceptibility of T. urticae, the Citrus oils and selected constituents were more effective by fumigation than residual contact. The C. reticulata oil was the most toxic by fumigation, and the C. limon oil was the most toxic by residual contact. The constituent alpha-terpineol exhibited the highest toxicity with both methods. At a sublethal concentration, the oils and selected constituents had significant effects on the fecundity, feeding preference and oviposition of the mite. Citrus oils and their constituents are potentially useful for the future integrated management of T. urticae due to their lethal and sublethal properties. However, further studies are needed to evaluate the action of these essential oils against non-target organisms and determine the cost-benefit ratio for the formulation of an acaricide harvested from agro-industrial waste from citric fruit processing activities for use in the integrated control of T. urticae.