## 4 Discussion
In addition, most LEM cannot survive outside the erinea for more than 24 h [39], meaning that mites that did not make their decision within the period of observation (24 h), ended up dead in the middle of the arena. As this method allows mites to walk freely, it is uncertain how long a mite stayed on either side of the slide. Hence, we did not evaluate the activity of the mites, but the proportion of mites choosing one specific odor over another and whether the compound repelled or attracted those mites. By assessing only their final choice, this experimental set-up might have decreased the chances of having undecided mites influencing the results. One may wonder why there was a variation in LEM response when offered the choice between leaf shoot vs. leaf shoot (control group). The non-infested lychee tissue used was field-collected. Individual lychee trees may be exposed to different biotic and abiotic conditions that in turn may influence nutrition or synthesis of defensive compounds. These factors can also affect mite behavior. In our study we were not able to control for this variation. Finally, LEM is a host specific criiophyid mite known to attack several lychee tissues [32]. Consistent with what has been observed in the field, here we showed that LEM's most preferred tissue were the new leaf shoots (Figure 5). The attacked young tissue and the erinea progress simultaneously, meaning that the infested old plant tissue only dies months after exploitation by the mite ([PERSON] et al. _in preparation_). Once new growth starts to form, mite infestation in new tissue prevails and soon the whole plant is infested. This is important information for the management of LEM. It is known that lychee trees undergo two to three waves of flushing each year, usually in the summer and early in the autumn in southern China [91]. Thus, this is a critical period for prophylactic treatments with pesticides. Once the new leaf shoots are protected, LEM spread within and between plants and therefore yield losses are expected to be suppressed. Here, we showed that there is the potential to use key terpenoids and aldehydes in the attraction or repellence of LEM to lychee plants. In the future, lychee VOCs or HIPV can be used to develop volatile-based management strategies against LEM. HIPVs, especially elicitors such as the plant hormones salicylic acid and jasmonic acid, could induce the plant defense system before insect attack [91; 92; 93; 94; 95]. In addition, a \"semiochemically assisted trap cropping\", which consists of the use of trap crops supplemented with lures, such as pheromones or kaironomes, can enhance the effectiveness of pest control [96]. All these strategies have contributed to the detection, monitoring, and manipulation of populations of native and invasive insect species around the world. However, these strategies have been barely investigated for mite control [97] and there are still significant knowledge gaps in the chemical communication in the acari compared to insects. As they are wingless organisms, we envision a management system for LEM focused on the use of attractant semiochemicals to lure and target them outside the erinea. Alternatively, repellents could potentially be used to protect new shoots from LEM infestation. Overall, by addressing LEM preferences to plant volatiles and specific plant tissues, we hope that new control strategies can be developed. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/biom13060933/s1](https://www.mdpi.com/article/10.3390/biom13060933/s1)]([https://www.mdpi.com/article/10.3390/biom13060933/s1](https://www.mdpi.com/article/10.3390/biom13060933/s1)), Figure S1: Images of the four erineum stages associated with different levels of LEM infestation. Photos of the leaflets showing the erinea were taken using an Apple iPhone 11 (f/18; 1/120 s; ISO-125). Photo background has been removed using Adobe [8] Photoshop CS 5.0. Figure S2: Preference of LEM to same lychee plant tissues.