Study finds thyme oil is an effective insecticide

Two insects compromise mango production in several regions Cryptoblabes gnidiella e Scirtothrips mangiferae. For its control, a study indicates good potential in the use of essential oils extracted from five species of thyme.

Researchers tested the oils of Thymus vulgaris, Origanum vulgare, Thymus argenteus, Thymus citriodorus e Origanum syriacum. The samples originated from Egypt and Saudi Arabia. Chromatographic analysis identified two major compounds: thymol and carvacrol. The highest concentrations of these compounds were found in T vulgaris (69,45% thymol) and O. vulgare (64,82% carvacrol).

The formulations were applied to infested mango inflorescences. The oils T vulgaris e O. vulgare presented the lowest lethal concentration values ​​(LC50) for both pests. Against Scirtothrips mangiferae, the oils killed 50% of the population with 18,93 ppm (T vulgaris) and 16,93 ppm (O. vulgare). For Cryptoblabes gnidiella, the LC50 were 183,32 and 164,68 ppm, respectively.

The isolated compounds thymol and carvacrol, applied separately, showed even greater toxicity. Thymol eliminated 50% of the thrips at 7,75 ppm; carvacrol, at 8,45 ppm. For the moth, the values ​​were 87,46 ppm and 84,39 ppm.

The study also evaluated the biochemical impact of these compounds on insect enzymes. Thymol and carvacrol significantly reduced the activity of digestive and detoxifying enzymes, such as phosphatases and glutathione-S-transferase. They also inhibited acetylcholinesterase, an enzyme essential to the insect nervous system.

Chemical analyses indicated T vulgaris as the plant with the highest levels of chlorophyll, carotenoids and antioxidants. Already O. vulgare had a higher flavonoid content. Both oils stood out as promising biological control agents.

Further information at doi.org/10.3390/insects16090922