Adjuvant Tip of the Month - March 2024

Water quality and weather conditions have a negative impact on various crop protection products (CPPs). Water quality influences many herbicides and insecticides. Dissolved cations in water antagonise the activity of various post-emergence herbicides, and alkaline water leads to the hydrolysis of some insecticides. Weather conditions like humidity and temperature also influence all CPPs. This means that CPPs give variable results depending on the water and weather and variable control can even happen on one farm using various water sources or where humidity levels differ. Fortunately, some adjuvants reduce the influence of water and weather and stabilise CPP activity over different conditions. Apply CPPs responsibly according to label recommendations, even when using adjuvants.

Water

Dissolved cations, water pH and buffering capacity will influence sensitive CPPs. This means that the efficacy of a CPP will deteriorate as the water quality becomes poorer. Fortunately, there are effective adjuvants like buffers and salt adjuvants to address almost all water quality issues, thereby stabilising the activity of the CPP. Water conditioners should be used when recommended by the CPP label, especially when the grower is unsure about the water quality on his farm. Many salt adjuvants have additional advantages and are often used as a standard practice to optimise and stabilise efficacy. Remember that water conditioners have limitations and cannot address all spray water issues. Adjuvants normally cannot solve the negative impact of turbid water, so the correct water source must be used.

Weather

Temperature and humidity are two of the main factors that can have a devastating impact on CPP efficacy. This already begins when the nozzle has released the droplet, and it starts evaporating in the air. When the leaf retains the spray droplet, rapid evaporation plays a further negative role. After the water has evaporated from the droplet, the CPP may lie on the leaf for an extended period. This is where low humidity and high temperature could further desiccate the droplet residual, limiting the amount of active ingredient available for effective control. Adjuvants like surfactants, oils and humectants help to keep the spray droplet residual conducive for prolonged activity of the CPP. This stabilises the efficacy of CPPs over different temperature and humidity levels.

Villa’s stance

Adjuvants play a crucial role in stabilising CPP efficacy over different water quality and weather conditions and often mean the difference between unacceptable and acceptable control. Never use adjuvants as an excuse to apply CPPs irresponsibly, and always follow the labels. When an adjuvant is recommended, use the specific brand name product. If this product is unavailable, contact the CPP registration holder for advice. Contact your Villa marketing advisor for more information about adjuvants and water quality.