## 3 Discussion
In the laboratory, it is difficult to determine which VOCs repel thrips better, as most _F. occidentalis_ chose clean air in the olfactometer bioassays. There have been numerous studies on plant volatiles that are attractive or repellent to _F. occidentalis_. In these studies, \(p\)-anisaldehyde, benzaldehyde, ethyl nicotinate, nonanal, and other plant-produced semiochemicals have been reported to attract _F. occidentalis_ in the laboratory, open field, and greenhouse [11; 39; 40; 41; 42; 43], while 2-phenylethyl acetate, \(\beta\)-ionone, methyl salicate, salicaldehyde and other semicohemicals were found to repel _F. occidentalis_ in the laboratory [27; 38; 44; 45]. In addition, \"insect pests-host plants-predators\" systems regulated by semiochemicals can be useful in biological control strategies for the management of thrips [11; 24; 32]. For example, methyl isonictimate can attract both _F. occidentalis_ and their anthocyanin predators (e.g., _Orius laevisatus_ (Hemiptera: Anthocoridae)) [46]. Here, although \(\beta\)-myrcene was attractive to _F. occidentalis_ at various concentrations, we focused on the repellent effects of VOCs on this thrip species for the purpose of pest control. Although decanal, dodecanal, and decanoyl acetaldehyde showed no attractiveness to _O. similis_, they were all repellent to _F. occidentalis_. Therefore, in the future, better control may be achieved by incorporating these volatile compounds as thri-repellent biopesticides with biological control releases of _O. similis_ in a mulitactic integrated pest management system. For interactions between thrips and host plants, prior to locating a potential host plant, thrips use plant volatiles as olfactory cues at a distance to avoid unsuitable hosts and at close range to avoid unsuitable plant parts. Therefore, based on the olfactory bioassays reported herein, _H. cordata_ can be considered as an unsuitable host plant species for _F. occidentalis_, and decanal, dodecanal, and decanoyl acetaldehyde have the potential to be developed as repellents or deterrents for the control of _F. occidentalis_. Repellents cause insects to move away from an odor source and prevent adult insects from landing on a plant, further preventing contact between the insect and the stimulus [11, 47, 48]; further, odorants present on the plant surface or in the plant can act after alighting and may inhibit feeding or oviposition. It is difficult to discriminate repellents from deterrents, because the volatilization of compounds may give provide olfactory input even after contact with the plant [49, 50]. In this manner, decanal, dodecanal, decanoyl acetaldehyde, and the other volatile chemicals identified herein should be further evaluated for their influence on the feeding, oviposition, and other behaviors of _F. occidentalis_ during interactions with host plants. This will help in better understanding the physicochemical characteristics of these chemicals (e.g., used as repellents or deterrents) and making full use of them for the management of thrips as pest species. It has been reported that repellent volatiles may be involved in the resistance of chrysanthemum and cowpea cultivars to _F. occidentalis_[33, 51], and these plants also show promise for developing cultivars with resistance to _F. occidentalis_.