Abstract
Simple SummaryDuring the steam distillation of aromatic plants, two main fractions are usually obtained: the hydrophobic essential oils and the hydrophilic fraction commonly known as hydrolate (HY). The essential oils are largely used in several industry fields, including the agricultural industry as biopesticides. Residual HYs, instead, are often discarded as by-products of little or no value. Our research pointed out that also HYs have biological activity, suggesting their potential use in plant-based strategy for the pest control. In more detail, we investigated the insecticidal properties of the hydrolate from Monarda didyma, scarlet beebalm, towards Drosophila suzukii. Using specific molecular and behavioural assays, we showed that M. didyma hydrolate affected the fitness and behaviour of D. suzukii, providing new insights in the D. suzukii control strategies through M. didyma hydrolate.Drosophila suzukii (Matsumara) is an herbivorous pest whose control in the field with conventional chemical is particularly difficult and has important drawbacks. Here, we investigated the insecticidal properties of hydrolate from Monarda didyma, scarlet beebalm, an aromatic herb in the Lamiaceae family. The identification of volatile organic compounds (VOCs) by CG–MS systems revealed that thymol (38%) and carvacrol (59%) were the most abundant VOCs in the hydrolate. M. didyma hydrolate did not show fumigant toxicity. Conversely, in contact assays, M. didyma hydrolate showed a LC50 of 5.03 µL mL−1, 48 h after the application on D. suzukii adults. Expression of detoxification genes increased in flies that survived the LC50 application. Furthermore, toxicity persisted for 7 days after the treatment in the survival evaluation. Artificial diet assays with 100 and 1000 µL mL−1 of M. didyma hydrolate resulted in a significant decrease in total food intake in both male and female D. suzukii adults. In addition, electropenetrography (EPG) showed that the D. suzukii females’ feeding behaviour was altered in hydrolate-treated diets. The hydrolate also caused a significant reduction in the number of eggs laid in two different oviposition assays. Overall, our findings provide a new perspective for the improvement of D. suzukii control strategies through M. didyma hydrolate.
Highlights
New and sustainable pest management strategies are needed to control the spread and damage of insect pests
Given the higher mortality in flies exposed to M. didyma, we investigated whether
Given the higher mortality in flies exposed to M. didyma, we investigated whether the treatment might trigger biomolecular responses such as the detoxifying systems of
Summary
New and sustainable pest management strategies are needed to control the spread and damage of insect pests. In this scenario, pest control requires more and more the identification of natural and environmentally friendly compounds with insecticidal activity. Plant-derived essential oils (EOs) are known to be important sources of natural insecticides to use in pest control [1–3]. Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), or spotted wing Drosophila (SWD), has successfully spread to Europe and the USA, and South America, Canada, and Africa, from its areas of origin (China, Taiwan, and Korea) [13–16]. Small red fruits (such as blackberries, raspberries, and cherries) are the most affected, but D. suzukii can attack other species, such as olives, spicebush, and mistletoe [17–19]
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