Dicamba, with its chemical name 3,6-dichloro-2-methoxybenzoic acid, has been an important "old soldier" in agriculture since its development by Velsicol Chemical Corporation in the early 1960s, thanks to its unique selectivity and systemic properties. It is a post-emergence auxin-type herbicide that controls weeds by mimicking plant hormones.

Dicamba's Mechanism of Action and Applications

Dicamba belongs to the benzoic acid series of herbicides and is rapidly absorbed by plant leaves and roots. Once inside the plant, it translocates through the phloem and xylem, accumulating in metabolically active sites. There, dicamba interferes with normal plant hormone activity, causing weeds to show abnormal curling within a short period, ultimately leading to their death within 15-20 days. Its high efficacy is demonstrated by its significant control of annual and perennial broadleaf weeds such as cleavers, lamb's-quarters, and cocklebur.

Notably, dicamba exhibits good safety on graminaceous crops (e.g., wheat, corn, millet, rice). This is because graminaceous plants can rapidly metabolize and break down dicamba, rendering it harmless and demonstrating strong resistance. Furthermore, dicamba has good stability in soil, with a residual effect lasting over 40 days, which is superior to other herbicides like 2,4-D. It is widely used in fields of asparagus, corn, sorghum, wheat, sugarcane, and also for controlling woody shrubs in cultivated areas.

Product Quality and Key Manufacturers

According to FAO regulations, the minimum content of dicamba technical material is 85%, while commercial products typically reach 98%. Globally, major manufacturers of dicamba technical material include Syngenta (Switzerland), BASF (Germany), Gharda Chemicals (India), and Zhejiang Huaxing Biochemical and Jiangsu Youxi Chemical (China).

Potential Side Effects and Precautions

Despite dicamba's effectiveness, its use requires caution. It is highly sensitive to dicotyledonous crops such as legumes, cotton, and potatoes, and therefore, its application on these crops is prohibited. When used on monocotyledonous crops, strict control of application time and dosage is necessary to avoid potential phytotoxicity. Mild phytotoxicity may manifest as loose plants, slanted or bent stems, or curled leaves, but usually recovers spontaneously within a week.

Dicamba is also volatile; under high temperatures, it can form mist droplets and drift to nearby sensitive crops, causing damage and yield reduction. Moreover, its migration in soil can lead to water body pollution and may affect soil microbial activity, negatively impacting soil fertility. These factors require particular attention during international registration and evaluation.

Development History and Integration with Genetic Modification Technology

The development of dicamba has evolved from single-agent formulations to multi-component pre-mixes. In its early days, Sandoz (now part of Syngenta) and PBI/Gordon were the primary sellers of dicamba products. Over time, companies like BASF, Syngenta, and DuPont successively developed various dicamba pre-mixes to broaden its application scope and enhance herbicidal efficacy.

Entering the 21st century, the use of dicamba in corn, soybean, and wheat fields globally has steadily increased. A significant turning point was the advent of genetically modified (GM) technology. Monsanto (now Bayer) collaborated with the University of Nebraska-Lincoln to successfully develop dicamba-resistant soybeans, enabling them to withstand high doses of dicamba. Subsequently, Monsanto introduced Dicamba+Glufosinate-Tolerant (DGT) cotton, a multi-trait GM crop resistant to both dicamba and glufosinate, further expanding dicamba's application in GM crops. The widespread adoption of these resistant crops has injected new vitality into this "old soldier," helping it address challenges such as weed resistance in modern agriculture.

Patent Situation

The compound patent for dicamba was filed by Velsicol Chemical Corporation in the United States in 1966 (US3345157) and published the following year. Currently, there are no patent barriers preventing domestic manufacturers from producing dicamba technical material. For formulation products, although various mixing methods may involve numerous cross-patents, reasonable circumvention strategies can usually prevent significant impacts on product launch.

With its unique herbicidal mechanism and broad application prospects, dicamba continues to play an important role in evolving agricultural technologies. Its integration with genetic modification technology offers new solutions for weed management challenges in the modern era.