Since the turn of the century, concern over the health impacts of chemical residues on fruit has led to increased demand for organically grown produce. Farmers have struggled to protect their crops and bring healthy produce into the system while still meeting organic standards. Pesticides based on herbal essential oils, including tea tree oil, are a potential answer to this problem. Though research is ongoing, tea tree oil is one essential oil that looks promising as a botanical insecticide against certain pests.
Tea tree oil is distilled from water-soaked leaves of the tea tree (Melaleuca alternifolia), so called because a much weaker, nutmeg-flavored tea can also be made from its leaves. The tree was named by 18th century sailors who discovered it on the swampy southeastern coasts of Australia, according to an article by the National Institutes of Health,
Tea tree oil is used topically for athlete's foot, some nail fungi and acne. It also has proven effective in cleaning and agriculture; its chemical compounds may interfere with the nervous systems of insects, while having no such effect on mammals (including human beings). As a vegetable-based horticulture oil, tea tree evaporates fully and does not leave a residue behind like petroleum-based chemical insecticides do.
As an Insecticide
Tea tree oil, as a vegetable-based oil, is thought to repel insects while also fighting leaf fungi. A 2002 report to Clemson University's Integrated Pest Management Program by Feng Chen, Patricia A. Zungoli and Eric Benson found that termites and German cockroaches avoided tea tree oil and that fire ants exposed to it had higher mortality rates. Tea tree oil, along with geranium oil, had significantly greater effect than other essential oils that were tested, including orange, rosemary and ginger oils.
Tea Tree Oil as a Disease-Fighting Agent
Timorex Gold, an insecticide using tea tree oil as its active ingredient, has been encouraged as a bio-fungicide by the Canadian government for use across Canada and in the U.S. since 2008. The uses recommended by the Canadian Pest Management Regulatory Agency (PMRA) and Agriculture and Agri-food Canada (AAFC) include fighting the apple scab disease but the agencies also encourage Timorex Gold use as a "reduced-risk, broad spectrum fungicide."
Make Your Own
You can talk to your local nurseries or home improvement stores about finding a compound like Timorex that's industrially manufactured, or you can simply make your own. Combine 2 tbsp. of tea tree oil with 2 cups of water. Pour into a spray bottle and shake well before applying. Spray onto the foliage of the plants you wish to protect. Use sparingly, only when you notice pests or fungus returning to your plants, as essential oils are strong and can burn your foliage if overused.