Silicone auxiliaries and precautions in the use of pesticides
Silicone-based surfactants are a type of silicone additive commonly used as spray aids in pesticide formulations. Compared to traditional spray adjuvants, silicone additives offer several distinct advantages. In addition to improving the wetting, spreading, and adhesion of the liquid, they can significantly reduce surface tension—often bringing it down to around 20 mN/m. This helps the spray solution penetrate plant surfaces more effectively, enhancing absorption through leaf pores. Moreover, these additives provide resistance against rain wash-off, which leads to better efficacy with less product usage. As a result, they help lower both the cost of pesticides and labor, while also reducing the physical burden on farmers. Due to these benefits, their use is becoming increasingly popular across China.
However, the application of silicone additives can sometimes lead to phytotoxicity. This occurs when the surfactant disrupts the cuticle layer of the leaf epidermis, reducing its ability to retain moisture and potentially causing cellular damage. The symptoms typically include chlorosis (yellowing) or drying of leaves, as well as brown spots or halos on fruits. These effects can seriously impact crop yield and quality. The likelihood of phytotoxicity depends on several factors, including the type of crop, the formulation of the pesticide, the concentration of the additive, the leaf surface area, and the temperature during application.
Crops with thinner wax layers—such as cucumbers, beans, and tomatoes—are more prone to damage than those with thicker waxy coatings, like rice, ginger, or onions. Additionally, different fruit varieties may react differently. For example, herbicides containing silicone additives (like chlorimuron-ethyl, nicosulfuron, or flufenazone) tend to carry a higher risk of phytotoxicity compared to insecticides or fungicides. However, even when used with insecticides or fungicides, silicone additives can still cause some level of plant injury. Higher concentrations and larger leaf coverage increase the risk, as do applications conducted at high temperatures.
To ensure safe and effective use, there are four key points to consider when adding silicone additives to pesticide mixtures:
First, always conduct a small-scale test before large-scale application, especially if you're unfamiliar with how a particular crop reacts to the additive. This helps prevent widespread damage.
Second, pay close attention to the concentration. Silicone surfactants are usually used at lower concentrations than conventional adjuvants. It’s recommended to keep the concentration below 0.1% by volume of the total spray solution.
Third, when spraying fruit trees, avoid direct contact with the fruit itself. If possible, apply the mixture after the fruit has been bagged to minimize exposure.
Fourth, avoid applying during hot weather. Pesticide manufacturers strongly advise against using silicone additives when temperatures exceed 30°C. Instead, it's best to spray early in the morning or late in the evening to avoid the intense midday sun.
By following these guidelines, farmers can maximize the benefits of silicone additives while minimizing potential risks to their crops.
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