Interspecific Eavesdropping on Chemical Communication in the Field between Taif Pomegranate, Aphis punicae, Enemies, and Protectors

The demand for alternative pesticides for agricultural crops is becoming a public health requirement. In nature, volatile organic compounds (VOCs) play a major role in influencing the qua-trophic relationship between plants, pests, protectors, and predators. By utilizing an ecological approach, these substances can be utilized as a powerful crop biocontrol tool for integrated pest management (IPM) against Aphis punicae , the green pomegranate aphid. This study involved collecting VOCs from aphid-infested pomegranates (AIP) in the presence of protectors and predators in the field for the first time in Taif Governorate to implement IPM. Using headspace open-loop stripping and gas chromatography-mass spectrometry analysis, 30 VOCs were identified from four ecological interactions between AIP, ants, and ladybirds. The VOC profile of AIP indicates that it is experiencing early injury due to low β-farnesene, methyl salicylate, and high caryophyllene. Principal component analysis, cluster analysis, and heatmap were used to identify the key volatile compounds in the field from the four systems studied and demonstrate the variability of the volatile compounds among different insects and host plants. Seven volatile compounds, including 1-methyl-3-tert-butylbenzene, m-ethylcumene, 3-carene, (+)-4-carene, 2,2,4-trimethyl-pentane, and caryophyllene, were detected in the ecological interaction of AIP. The primary ant pheromone compound, 4-heptanone, becomes effective in repelling aphids after 24 hours when ants and ladybirds are present. In 48 hours, a complex pattern was observed consisting of 1-ethyl-3-methylbenzene, 1,3,5-trimethylbenzene, and 1-methyl-1H-imidazole, which was identified as a key factor in repelling aphids. The same ecological system showed that methyl salicylate, sabinene, limonene, pentadecane, and heptadecane were found to attract predators. The composition and quantity of VOCs emitted can cause varying responses. This study serves as a basis for future quantitative studies that can determine the concentration of each volatile compound that is essential for the biological control of A. punicae .