Acaricidal Activity of Botanical Oils Against Tetranychus urticae and Their Non-Target Effects on Amblyseius swirskii and Photosynthesis in Papaya

Abstract

The objective of this study is to evaluate the effects of botanical oils on the mortality of the phytophagous mite Tetranychus urticae, the predatory mite Amblyseius swirskii, and on gas exchange in papaya seedlings. Two vegetable oils (soybean and corn), two essential oils (lavender and oregano), a synthetic pesticide (abamectin), and a control (water) were evaluated on papaya seedlings infested with T. urticae. In laboratory assays, within the first day after application, abamectin caused 100% mortality of T. urticae adults, followed closely by soybean (96%), corn (94.7%), and lavender (94.7%) oils. In A. swirskii, abamectin caused 100% mortality within 24 h; at 72 h, corn and lavender oils reached 96%, while oregano oil caused the least mortality (67.3%). In field trials, both abamectin and botanical oils statistically reduced eggs per leaf 24 h after application relative to the control, and a similar pattern was observed for nymphs 48 h after treatment. Botanical oils equaled abamectin in T. urticae adult suppression by 72 h, and soybean caused complete adult mortality by day 14. Regarding gas exchange, abamectin significantly affected the photosynthesis and transpiration processes. Thus, botanical oils represent viable biorational options for managing T. urticae in papaya, with lower ecological and physiological costs than abamectin.