Agricultural practices to improve the production of food crops have undergone a drastic transformation in recent years. Owing to the chemical-free production process, organically grown food crops are popular among both consumers and farmers. While greener alternatives to fertilizers have been explored, there remains a critical need for sustainable pest management practices to improve food productivity. Moreover, chemical-based pesticides have the potential to negatively impact the environment, biodiversity, and ecosystems.
To address the lack of natural pest control agents, scientists across the globe have turned their attention to companion planting–a practice where two different plants are grown in close proximity to benefit each other. These plants can communicate with each other and are referred to as "talking plants." Some reports indicate that growing fragrant plants like mint or certain grass varieties can significantly increase anti-herbivore properties and boost the natural plant defense mechanisms of the neighboring plants.
In this light, a team of researchers led by Professor Gen-ichiro Arimura from the Department of Biological Science and Technology, Tokyo University of Science, Japan, has co-cultivated the common bean (Phaseolus vulgaris) plant with fragrant bush basil (BB). Their research findings have been published online in the Journal of Agricultural and Food Chemistry on July 04, 2025.
Fundamentally, fragrant herbs like BB are capable of communicating with other plants by emitting volatile organic compounds (VOCs) from their leaves. Leveraging the VOCs emitted by BB plants, the team of researchers evaluated the subsequent changes in plant defense mechanisms in the common bean plant. They found that VOCs emitted from the BB plant increased the expression levels of the pathogenesis-related 1 (PR1) gene in the leaves of nearby common bean plants.
"We undertook this research with the aim of utilizing talking plants that emit VOCs to improve agricultural practice, accumulate scientific knowledge regarding plant communication, and lay the foundation for extending this technology to be used in agricultural fields," says Prof. Arimura, explaining the motivation behind the present study.
In further experiments, the researchers strived to assess the impact of co-cultivating the common bean plant with BB on agricultural pests. They employed two plant pests—Spodoptera litura, a chewing herbivore, and Tetranychus urticae (spider mite), a small plant-sucking herbivore and monitored their egg-laying activity on plant leaves. In common bean plants cultivated with BB, decreased egg-laying activity of adult female T. urticae was observed. Additionally, the researchers found that growing common beans, alongside BB, not only triggers the beans' own defenses, but also attracts Phytoseiulus persimilis—a natural enemy of spider mites. Remarkably, the basil's VOCs alone also served as a powerful lure for attracting P. persimilis. These discoveries together point to a simple solution: planting common beans at least 100 cm apart, representing an effective range from the BB, can significantly cut pest damage in the field.
Elated with their findings, the scientists then focused their efforts on determining the biochemical composition of VOCs emitted by BB plants. They identified two chemicals, linalool and eugenol, as the key components that make up the VOCs. However, only eugenol, when placed close to the common bean plant, could increase the expression of the PR1 gene in leaves.
Elaborating on the benefits of co-cultivating with BB, Prof. Arimura states, "Aromatic plants such as candy mint and BB have the ability to activate or awaken the pest resistance of surrounding plants through their aroma. Utilizing this mechanism may enable environmentally friendly and efficient pest management. There are high hopes for talking companion plants like BB and mint as they hold the key to the sustainable agriculture of the future."
While the complete elimination of pesticides is nearly unfeasible, the researchers demonstrate that the pest damage can be reduced to less than 20% using the companion plants, thereby reducing the usage of pesticides significantly. Also, this study proves that the co-cultivation of BB near the food crops emerges as a sustainable alternative, with no limitations. This technique is quite easy to implement and has been proven effective for crops such as soybeans and tomatoes.
Taken together, this study reveals a dual mechanism involving the VOCs emitted by BB to improve plant defense mechanisms and protect against agricultural pests.
