Plant-based volatile compound enhances the effectiveness of insecticides against the Helicoverpa armigera caterpillar

The (Z)-3-hexenyl acetate has increased the effectiveness of plant-derived compounds and synthetic insecticides against Helicoverpa armigera, according to a study by Chinese scientists, the volatile plant compound is a possible natural synergist for managing the caterpillar. The effect occurred through interference in the detoxification system mediated by cytochrome P450.

The compound, identified by the acronym HAC, belongs to the group of green leaf volatiles. The plant releases this class of substances after herbivore attack. Researchers highlight HAC as a herbivory-induced volatile with the potential to reduce limitations associated with other synergists, such as production costs and biosecurity concerns.

The study evaluated the interaction of HAC with plant secondary metabolites and synthetic insecticides. Among the plant compounds, the tests included flavonoids, tannic acid, and coumarin. Among the insecticides, the researchers analyzed emamectin benzoate, spinetoram, tebufenozide, chlorfenapyr and chlorantraniliprole . The HAC increased the toxicity of these products to the caterpillar.

Detailed assessment

Emamectin received a more detailed evaluation. Researchers used this ingredient as a representative compound in greenhouse bioassays. In these tests, exposure to HAC and foliar application of the volatile enhanced the insecticidal action under natural protected cultivation conditions.

Transcriptomic and enzymatic data indicated a profound alteration in detoxification regulation during emamectin-induced stress. Cytochrome P450 gene expression and mixed-function oxidase activity increased after isolated exposure to HAC or emamectin. However, co-application of the two products strongly suppressed these responses.

Synergism mechanism

This result suggests a synergistic mechanism. HAC not only adds to the insecticide's effect, but it also interferes with a pathway used by the insect to metabolize toxic compounds. With impaired detoxification, the caterpillar loses some of its ability to neutralize emamectin.

Researchers link the finding to the problem of metabolic resistance. Intensive use of insecticides favors populations with a greater capacity for detoxification. This response reduces control efficiency and stimulates new application cycles. Combining with synergists can increase the efficiency of the active ingredients. It can also reduce the pressure for higher doses or additional applications.

Scientists cite limitations of synthetic synergists already used in commercial formulations. Piperonyl butoxide, for example, appears as a compound associated with ecological and toxicological concerns. Complex formulations also face regulatory barriers. In this context, plant substances with synergistic action are gaining interest for integrated pest management programs.

The study positions HAC as a candidate for sustainable management of Helicoverpa armigera. The scientists' conclusion indicates the potential use of the volatile compound as a natural synergist for biological and chemical insecticides.

More information at doi.org/10.1127/entomologia/3790