Theseus Mauruki Shambare in VICTORIA FALLS
TOBACCO waste could find a new use in agriculture, with research showing that bio-oils extracted from the crop’s stalks, stems and leaves have the potential to control insect pests and suppress crop-damaging fungal pathogens.
The findings were presented yesterday by Dr Tânia R. Cabrito of Philip Morris International (Portugal) as the 70th CORESTA Congress, hosted by Zimbabwe under the leadership of the Tobacco Research Board (Kutsaga), drew towards its conclusion in Victoria Falls.
The study, titled “Tobacco-based pyrolytic bio-oils as biopesticides: defence against Phthorimaea operculella and fungal infections”, investigated the potential of tobacco-derived bio-oils as biological crop-protection agents.
Conducted in collaboration with researchers from Philip Morris International’s research and development teams in Switzerland and Brazil, as well as an independent researcher in Germany, the study examined bio-oils produced from tobacco stalks, stems and leaf lamina.
Laboratory experiments showed that the bio-oils could cause more than 80 percent mortality among potato moth larvae, while completely inhibiting fungal growth in tests involving four crop pathogens.
Presenting the findings, Dr Cabrito said the results demonstrated the potential of tobacco-derived compounds to offer alternative approaches to agricultural pest and disease management.
“We proved that bio-oils are actually toxic for the potato moth larvae in both ways, with both methods,” she said, referring to preventive treatment and application after infestation.
She said bio-oils extracted from stems and leaf lamina, applied at a five percent concentration, caused more than 80 percent mortality among potato moth larvae under one of the experimental treatments.
The research also tested the bio-oils against Fusarium, Rhizoctonia, Pythium and Phytophthora, pathogens associated with crop diseases.
At a concentration of 2.5 percent, all four bio-oils achieved 100 percent inhibition of fungal mycelial growth in laboratory tests.
“They actually matched or even beat the commercial biological standard,” Dr Cabrito said, highlighting their performance against Fusarium and Rhizoctonia.
The research also found that nicotine alone could not explain the observed pesticidal and antifungal effects, suggesting that other compounds, including phenolics and organic acids, could be contributing to their activity.
The findings prompted questions from Miss Debra Chamboko, an independent researcher affiliated with Kutsaga, who sought clarity on the appropriate timing of application, particularly during crop growth and after harvesting.
Responding, Dr Cabrito said application strategies would depend on the target pest and its development cycle, adding that greenhouse seedling production could be one area for further investigation.
“For potato moth, when you have production of seedlings, it could be a problem in a greenhouse,” she said.
She said soil-borne fungal pathogens might require treatment at different stages, potentially before transplanting, depending on how the bio-oils could be applied.
However, Dr Cabrito cautioned that further research was needed to establish the chemical composition of the bio-oils and validate their effectiveness under field conditions.
“We need to further assess the phytotoxicity of these compounds in relevant crops, tobacco included,” she said.
She also acknowledged that existing pyrolysis systems were not optimised for bio-oil production, resulting in low yields and potentially high production costs.
The next phase will involve semi-field experiments, including trials on potted plants, to establish suitable application methods, crop safety and practical effectiveness.
Dr Cabrito said the research offered an opportunity to add value to secondary tobacco products through circular-economy approaches, potentially turning agricultural waste into useful crop-protection products.
“We actually established this proof of concept. Tobacco bio-oils can act as these multifunctional pesticides,” she said.
