Bioactivity and physico-chemistry of garlic essential oil nanoemulsion in tomato

Tomato has an economic relevance worldwide but its production is threatened by several biotic factors, including the invasive South American tomato pinworm Tuta absoluta. The control of this pest mainly relies on the repeated applications of synthetic insecticides that can have considerable non-target effects; therefore, new sustainable control approaches are required. The biocidal activity of garlic has been recognized and no risks for consumers and the environment are expected in its use. However, the practical implementation of garlic extracts is hampered by several drawbacks that could be overcome by nanotechnologies. We developed and characterized a new garlic essential oil-based nanoemulsion (GEO-NE) and laboratory trials were carried out to investigate its insecticidal activity against T. absoluta involving different instars and exposure routes. GEO-NE side effects on the mirid predator Nesidiocoris tenuis and tomato plants were also assessed in the laboratory. The nanoformulation had dimensions belonging to the nanometric scale and good stability over time. GEO-NE showed significant toxicity towards T. absoluta eggs and larvae and repellence for ovipositing females. No lethal effect on N. tenuis adults was recorded but its progeny was significantly reduced on GEO-NE treated plants. By contrast, GEO-NE had no phytotoxic effects on sprayed tomato plants. Our findings suggested that GEO-NE can successfully control T. absoluta and its application deserves to be considered as a potential tool for tomato Integrated Pest Management.