Capturing Better Seed Solutions through Formulation Optimisation

The high performance requirements and complexity of seed treatments, means formulating is the focal challenge. Seed treatment formulations usually contain multiple active ingredients and/or high loading levels. In addition, treatments must not reduce the quality of the seed or be detrimental to germination. Instead they should provide “added value” to the grower, such as better emergence and/ or seedling establishment, improved crop health, quality and yield. 
 

Seed treatments have grown in popularity and have significantly advanced since their first realisation. The use of insecticides and fungicides has steadily increased since the 1940s until the early 1990s, which subsequently saw exponential growth following the introduction of new technologies in the late 1990s. The global seed treatment market was valued at $4.8 billion in 2014 and is expected to achieve CAGR of 10.8% per year to reach in excess of $8.8 billion by 2020.¹ 
 

The challenges associated with developing a seed treatment are multifaceted, requiring optimised efficacy in the field balanced with ease of use, meeting safety regulations for workers, and environmental responsibility, including stewardship of resistance management. 
 

Seed treatments are agronomically tailored to deliver combinations of fungicides, insecticides, herbicide safeners, nematicides, and biologicals to give broad contact and systemic activity with multiple modes of action. 
 

The most popular formulation type for seed treatments is flowable concentrates (FS). They are considered to be very similar to suspension concentrates (SCs), as the continuous phase is water. 
 

The active ingredients are typically mixed with a polymer or copolymer and fillers such as talc, graphite, aluminium or calcium salts, and pigments. Alternatively the polymers can be applied separately as a liquid final protective coating, often within a colorant product. 
 

To date, an array of materials designed for other industrial uses (such as adhesives and coatings) have provided film formation and/or binding properties to seed treatment formulations. 
 

Such polymers have many roles in seed treatment formulations, including: 
 

● Protection of high value seed 

● Uniform seed coverage, for optimum seed flow in bagging and precision planting 

● Adhesion/fixation of treatment to the seed surface, remaining in-tact throughout storage 

● Optimised/precision dosing of active ingredient 

● Reduced friction and abrasion of seeds during storage and planting 

● Reduced dust-off from treated seed, during drilling and residue in seed bags 

● Application of colour for identification of treated seed (in particular GM) 

● Contribution to increased germination, vigour and crop health 

● Improved cosmetic appearance 

● Durability 
 

Speciality polymer suppliers, such as Croda, are met with a real opportunity in the development of innovative, customised materials for seed treatment. In combination with this, the capability for offering formulation expertise with the knowledge and support for testing in this area will provide differentiation to a customer seeking bespoke solutions. 
 

For example, high performance polymers and specialty ingredients, such as those in Croda’s Seed Vision™ range, are able to offer benefits to the application of established active ingredients. In the case of Metalaxyl-M, registered for use by EPA in 1983 and now for use on more than 50 crops globally, optimisation of its formulation e.g. as a microemulsion for improved performance offers advantages to the market. Microemulsion (ME) seed treatment formulations are a relatively new concept. They are thermodynamically stable and have an indefinite shelf life. They have a lower viscosity than FS formulations which results in better pourability and lower container residue. High surfactant levels in a ME formulation assist spreading onto the seed surface through reduced dynamic surface tension. Simple to manufacture at room temperature, their small droplet size provides better coverage on the seed, therefore allows lower application rates. 

Formation of a microemulsion can be achieved using off-the-shelf emulsifier blends, such as Atplus™ 310, to produce a Metalaxyl-M ME (loading 350 g/L).² Comparative germination testing (Images 1 and 2) shows that formulation optimisation can outperform a leading commercial benchmark. 
 

Seeds treated with this formulation were also shown to have improved performance in wet and dry flow measurements following treatment (Figure 1). 
 

In summary, today’s growers have to encounter huge challenges in crop production to meet rising demands for food production in a sustainable manner, midst an array of mitigating factors. Seed treatment offers some key advantages in helping to deliver optimised crop yield and health through agronomic selection of active ingredients and importantly advanced formulation ingredients and expertise.