_applied sciences_  
_Article_  
**Relationships between Volatile Organic Compounds Released by Wheat Plants Following Artificial Stress and Their Potential Influence on Natural Pest Management**  
**[PERSON] 1,*(c)**, [PERSON] 1, [PERSON] 2(c)**, [PERSON] 3(c)**, [PERSON] 4, [PERSON] 5 and [PERSON] 6(c)  
In recent years, natural and environmentally safe practices for farming have been investigated extensively, and a key one is the use of plant-emitted volatile organic compounds (VOCs) as elicitors of natural defences against pests [2; 3; 4; 5].  
The plant VOCs, which are linked to efficient defence strategies against various pests, include hexanal, (\(Z\))-3-hexanal, (\(E\))-2-hexanal, (\(Z\))-3-hexan-1-ol, (\(E\))-2-hexan-1-ol, \(\beta\)-caryophyllene, (\(E\))-\(\beta\)-farmesene, and (\(Z\))-3-hexan-1-yl acetate [6; 7; 8; 9]. The possibility of using induced VOCs to enhance the natural defence mechanisms of plants and hence protect crops is a particularly attractive and reasonable strategy, which could help to reduce our dependence on commercial pesticides. This could be achieved, for example, by the deliberate release of plant volatiles that are associated with signalling and defence methods in order to prepare a whole crop against pest invasion.  
A number of biotic and abiotic stress factors induce plant VOC emissions. An obvious biotic stress is that resulting from insect feeding, with signalling volatiles being released by the damaged plant informing other plants to prepare for a likely attack [7]. Physical damage by deliberate (mechanical) plant tissue injury will also induce the release of VOCs, as too can the exposure of plants to exogenous volatile compounds, such as methyl jasmonate (MeJA) or (\(Z\))-11-hexadecenal, which elicit stress responses. These can be used to influence plant VOC synthesis and secretion pathways [5; 10]. Finally, the specific use of genetically modified plants to emit particular VOCs has the potential to provide indicators for other plants to increase defence VOC emissions [2].  
The introduction of natural and efficient pest control strategies into the farming practice would bring huge societal benefits, but this can only be fully realised if we have ways to monitor their effectiveness and their effects on the environment. This is particularly crucial if the natural pest control strategies are to be used on an industrial scale, for which it needs to be shown that they are reliable, safe, and easy to use.  
To further our understanding of the use of plant volatiles for use as natural pest control, we present here studies of the release of volatiles from spring wheat (_Triticum_ L.) following either mechanical wounding or exposure to MeJA (either as a vapour or directly sprayed onto the plants). We also describe the effects of exposing the identified volatiles on a shield bug, the Bishop's Mitre. The Bishop's Mitre (_Aelia acuminata_ L., Hemiptera: Pentatomidae) is a common and dominant species of shield bug that causes kernel damage in wheat across Europe [11]. The threat they present is currently limited, but with increasing global warming the impact of Bishop's Mitre shieldbugs, and sunbugs in general, on wheat cultivation is significantly increasing [12]. A key hypothesis of the study is that the common biosynthetic pathway for most VOCs released by _Triticum_ L. will result in correlated levels of their emission, which could be used to predict the health of plants and the presence of pests or diseases in cultivation. A major objective of this study is to demonstrate that MeJa can be used to activate the natural defence system of spring wheat prior to an insect attack.