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WWW.POTATOGROWER.COM 29 Activity and MOA At suitable concentrations, Regev significantly inhibited spore germination or lesion development on treated leaves, and limited the expansion of lesions caused by various fungi. Diseases effectively controlled by Regev include powdery mildews (caused by fungi in the order Erysiphales), apple scab (Venturia inaequlis), black Sigatoka in banana (Mycosphaerella fijiensis), species of Alternaria, Cercospora, Botrytis, Rhizoctonia, Pyricularia, Helminthosporium, Sclerothium and more. The fungicidal and antimicrobial activities of tea tree oil against fungal pathogens are derived from its ability to inhibit respiration and disrupt the permeability barrier presented by the membrane structures of living organisms. Tea tree oil was found to disrupt the fungal cell membrane and cell wall in plant tissue infected with phytopathogenic fungi. This explains why it exhibited outstanding curative activity against fungal pathogens, making it a unique product and enabling growers to use it even when the disease is already visible on the tissue. Difenoconazole affects the fungal cell membrane by inhibiting ergosterol biosynthesis. The mode of action of sterol biosynthesis inhibitors, including difenoconazole, has been investigated extensively. The different modes of action of tea tree oil and difenoconazole makes Regev an effective and unique tool for resistance management which is suitable for integrated pest management programs. This combination results in a reduced synthetic chemical load on the environment compared to other mixtures based on two traditional chemicals. Resistance Management Because Regev has a unique multiple functional activity and presents a very low probability for development of resistance or cross-resistance in plant pathogens, it could be an important tool in preventing the development of resistance during the growing season. Its application can be rotated with products that exhibit different modes of action and to which fungal pathogen populations have shown a loss of sensitivity, so that the population of individuals that are less sensitive to chemical products can be reduced. Studies have also shown that a combination of tea tree oil and difenoconazole improved the efficacy of difenoconazole, including against fungal populations that had exhibited a lower sensitivity to difenoconazole. Summary Historically, biopesticides have been used largely on high-value crops, such as fruits and vegetables, but hybrids like Regev are not only being used on fruits and vegetables, but have proven to be a cost-effective approach for row crops like soybeans, and field and broad-acre crops like corn. Regev is expected to prove an important component in plant disease control thanks to its preventive and curative activities; the indirect activity via the host plant either by systemic resistance or enhancing plant growth and yield; and the fact that it is reliable, leaves little residue and provides significant added value to growers. Its activity has been shown on a wide range of plant diseases. Regev promises successful yields without risking profit margins while simultaneously upholding regulations and responding to growing consumer demands. It represents a new generation in the future of crop protection. Moshe Reuveni is chief scientist at STK Bio-Ag Technologies in Israel, where he has been involved for nearly two decades in developing new, plant-based biopesticides.