## 6 Tephritid Sexual Chemoecology: Real-World Applications and Challenges
### Push and Pull Approaches Based on Repellent Semichemicals  
HMPs have been regarded as attractive tools for tephritid pest control since the '70s. In 1976, Katsoyannos and Boller proposed to use HMPs to prevent fruit fly oviposition into the fruit. They performed the first field experiment spraying raw HMP extract obtained from the faecal matter of _R. cerasi_. In this way, they achieved over 90% reduction of _R. cerasi_ infestation in cherries orchards [501; 502]. Later, once the chemical structure and the synthesis of _R. cerasi_ HMP have been obtained [29], Aluja and Boller [31] tested the synthetic _R. cerasi_ HMP in the field and, interestingly, this was the first application of a \"push-pull strategy\" in fruit flies. A push-pull strategy exploits a combination of behaviour-modifying stimuli to manipulate the distribution and abundance of the insect targets. Pests are repelled from their resource (push) by using stimuli that mask the host or that acts as repellents. Simultaneously, they are driven away from the resource (pull), by using highly attractive stimuli such as traps, facilitating their elimination. A reduction of the infestation of about 90% in cherry plants was achieved by treating one half of tree canopies with a synthetic HMP. The repelled females were then trapped with visual traps placed on the other half of the canopy [31; 503]. The efficacy of the synthetic HMP was further supported by another field trial in which the infestation by cherry fruit flies was eliminated [504].  
Similarly, field tests were performed using raw pheromone extract from the medfly's faecal matter achieving 84% decrease in infestation in sprayed coffee plants [390]. Exploiting the cross-recognition observed in the _Anastrepha_ genus, Aluja and co-workers tested three potential oviposition deterrents for _A. obliqua_ in tropical plum and mango orchards. In their experiments, they used _A. ludens_ faecal extracts and two fully synthetic simplified analogues of the naturally occurring pheromone, namely desmethyl _A. ludens_ HMP (DM-HMP) and anastrephamide. They obtained a significant reduction in fruit damage rates with all substances tested, and interestingly, the simplified analogues displayed comparable levels of efficacy to the natural HMP [32].  
The good efficacy of the synthetic HMP analogues found in both _R. cerasi_ and _A. obliqua_ field tests is promising in view of their potential use as pest control strategy. However, there is evidence that, after prolonged exposure to the HMP, flies can lay eggs in the treated fruits. This behaviour could be associated with the sensorial adaptation by the insect [123; 503].  
Although the use of HMP in the management of fruit flies was initially suggested as a push-pull system [32; 112; 393; 400; 505], the push-pull strategy is not suitable for the species with high population growth rates [506]. A recent work used anastrephamide in combination with a protein bait to reduce grapefruit infestation by _A. ludens_[507]. The authors found that anastrephamide can push flies out of the treated tree, but the push-pull system requires a more effective attractant.  
Lastly, an alternative use of HMP has been proposed, which implies HMP application in commercial crops in which the fruit fly populations are not resident. This option allows achieving pest suppression because of the small population and lower risk for the occurrence of adaptation [114].