Pesticides are widely used in agriculture to control pests, diseases, and weeds. However, the release characteristics of their active ingredients play a critical role in determining their effectiveness and environmental impact. Based on these release properties, sustained-release pesticide formulations can be broadly categorized into two types: free-release conventional and controlled-release dosage forms. Conventional pesticides typically have a low utilization rate—only 20% to 30% of the applied product is actually effective—while up to 50% to 60% is lost through runoff, volatilization, or degradation. This not only leads to economic waste but also causes significant environmental pollution. As a result, controlling the release amount, timing, and spatial distribution has become a major focus in the development of new pesticide formulations.
The core principle of controlled-release technology involves the interaction between the pesticide's active ingredient and a polymer compound. This allows for a continuous and gradual release of the pesticide into the environment over time, according to a pre-set concentration and duration that aligns with pest control needs. The sustained release mechanism helps maintain a stable concentration of the active ingredient, reducing the impact of external factors like water and air. Moreover, this approach extends the duration of the pesticide’s effect, allowing for lower application rates and reduced overall usage. This, in turn, minimizes residue accumulation and environmental risks. Additionally, slow release can reduce the toxicity of the pesticide to both target pests and non-target organisms.
Pesticide sustained-release agents are generally divided into physical and chemical types. Physical agents involve the dissolution or mixing of the active ingredient within a polymer matrix, such as in microcapsules, inclusion complexes, or adsorbents. Chemical agents, on the other hand, rely on the formation of chemical bonds between the pesticide and the polymer. While many commercial products use physical methods, especially microcapsules, the development of sustainable release technologies remains challenging due to high production costs and limited market competitiveness.
Since the introduction of microencapsulated methyl parathion by Pennwalt in 1974, sustained-release technology has gained attention in the pesticide industry. Although over 20 products have been developed, their market share remains limited. In China, similar microcapsule formulations were once produced but failed to gain widespread adoption due to various technical and economic barriers. Overall, the development of sustained-release agents has been slow, primarily due to high material and processing costs.
Research into slow-release pesticides has focused on identifying cost-effective materials. For example, the Beijing Agricultural Technology Extension Station has explored natural polymers as low-cost alternatives. Through specialized processing techniques and testing methods, they have developed a range of sustained-release materials, including those with uniform and non-uniform "S" curve release profiles. These materials allow for better control over the release dynamics of the pesticide, making them more adaptable to different crop needs.
In practical applications, slow-release formulations have shown promising results in managing vegetable pests and diseases. When combined with systemic insecticides like imidacloprid or aktai, these formulations are processed into root-pesticide pellets or granules. During planting, the active ingredient is gradually released into the soil, absorbed by the plant, and transported upward to control pests. This method ensures early protection when pest populations are low, reducing the need for multiple applications. Field trials have demonstrated improved efficacy, with sustained-release aketai granules showing significantly higher control rates compared to conventional formulations.
In cotton cultivation, slow-release pesticides have also been used to manage plant growth, helping to control plant height and promote early maturity. While foliar applications have traditionally been used for defoliation, the integration of sustained-release technology offers a more efficient and targeted approach.
This article was published by the **China Pesticide Network**. Please cite the source!
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