Potatoes rank as the fourth most important crop globally after rice, wheat, and maize, and serve as a staple food for over half a billion people worldwide (1, 2). More than a billion people consume potatoes, recognising them as a superior vegetable crop due to their high nutritional value (2).
However, this vital crop faces a formidable threat: Potato Late Blight, a highly virulent disease caused by the pathogen Phytophthora infestans. Under favourable conditions, this disease can devastate entire fields within just two weeks, often leading to complete crop loss (3). Notably, this same pathogen was responsible for the Great Irish Famine in the 1840s, a tragic event that resulted in over a million deaths and forced the emigration of two million more (4). Given the aggressive nature of P. infestans, effective management strategies are essential. These include the use of fungicides while carefully rotating chemical groups to prevent the development of resistance (2). Late blight is a polycyclic disease, meaning it can produce multiple infection cycles in one season, affecting both the above-ground parts and root systems of the plant (3). In South Africa, the regions most affected by late blight are the cooler parts of KwaZulu-Natal and the Sandveld area during the winter months (3).
Life Cycle of Phytophthora infestans
The life cycle of Phytophthora infestans begins with infected seed tubers, plant debris, or wild Solanaceae hosts, which act as the primary source of infection. Under humid conditions and temperatures between 18–24°C, the pathogen produces sporangia on infected leaves. These are spread by wind, rain, or irrigation, allowing the disease to move quickly through a field.
Sporangia can germinate directly or release zoospores, which infect plant tissue at 13–16°C in the presence of free water. The pathogen enters through stomata or wounds and colonises the leaf’s internal spaces, causing rapidly expanding, water-soaked lesions. Sporangia may also reach the soil and infect developing tubers, leading to rot in the field or during storage. In areas with both mating types, oospores can form, allowing the pathogen to survive in soil between seasons (2,3).
Why COPRWET™ is a Powerful Fungicide
COPRWET™ is a suspension concentrate, contact fungicide that contains 300 g/ℓ copper oxychloride (CuOCl) as its active ingredient. It works by slowly releasing copper ions, which are toxic to fungi and bacteria. These ions disrupt key cellular processes in pathogens, effectively inhibiting spore germination and fungal growth.
What sets COPRWET™ apart is its efficiency with reduced copper content. It delivers the same level of disease control while using 40–60% less copper than conventional copper-based fungicides, making it both effective and environmentally considerate.
The formulation is stable and flowable, and includes OROWET® Technology, eliminating the need for an additional adjuvant. This built-in technology enhances performance by:
- Forming an optimal protective film on plant surfaces
- Ensuring strong adherence and excellent coverage
- Creating a reservoir of copper ions
- Providing a controlled, sustained release of copper over time
As a contact fungicide, COPRWET™ acts on the surface of plants to prevent infection, rather than cure existing disease, making it a key tool in proactive crop protection strategies.
Using COPRWET™ to Shield Your Crops
A field trial conducted in the Sandveld region of South Africa demonstrated the effectiveness of COPRWET™ compared to the industry-standard copper fungicide. Despite using 40–60% less copper, COPRWET™ delivered equivalent levels of disease control.
The first evaluation, carried out five days after the fifth application, showed moderate disease severity, with approximately 20% of leaves infected. At this stage, all copper-based treatments, including COPRWET™, provided very effective control. A second evaluation, completed seven days after the sixth application, revealed a significant increase in disease pressure, with 81% disease severity observed in untreated plots.
Despite the intensified infection, copper-containing products continued to deliver strong disease control, and COPRWET™ maintained its efficacy. These results confirm that COPRWET™ provides robust, reliable protection, even under high disease pressure, while significantly reducing copper input.
Conclusion
COPRWET™ is a user-friendly, flowable formulation with a vibrant blue colour and a fresh citrus scent, making field application both easy and pleasant.
References
- Tadesse, Y., Amare, D. and Kesho, A. 2021. Recent Advances in Potato Late Blight Disease Management Strategies.
- Tiwari, I., Shah, K. K., Tripathi, S., Modi, B., Subedi, S., & Shrestha, J. 2021. Late blight of potato and its management through the application of different fungicides and organic amendments: a review. Journal of Agriculture and Natural Resources, 4(1), 301–320. https://doi.org/10.3126/janr.v4i1.33374
- Potatoes South Africa. (2019). Fact sheet: Late blight http://www.potatoes.co.za/document-library
- Phytophthora infestans. 2025, April 8. In Wikipedia. Retrieved from https://en.wikipedia.org/wiki/Phytophthora_infestans
- Lamichhane, J.R., Osdaghi, E., Behlau, F., Köhl, J., Jones, J.B. & Aubertot, J.N. (2018). Thirteen decades of antimicrobial copper compounds applied in agriculture. A review. Agronomy for Sustainable Development 38(28). Available from: https://doi.org/10.1007/s13593-018-0503-9[ES1]
