Deltamethrin Formulations: The Good, Bad and Downright Ugly – Part 3

The third of a three-part series looking at the science behind deltamethrin formulations. Written by David Priddy, CEO of Sundew Solutions.

Deltamethrin products not only vary in the way they work, but how they look, perform, and even smell. The reason for this level of variation comes down to three key factors that influence the performance of a suspension concentrate deltamethrin formulation. These factors are particle size, plant hygiene and rheology. In this third article in the series we’ll explore the role of rheology and its importance in formulation performance.

Rheology, in the context of pesticide products, refers to the study of how these products flow and deform under various conditions. It involves understanding the physical properties and behaviour of pesticide formulations, such as their viscosity, shear rate, and thixotropy (shear thinning properties).

Rheological measurements are critically important for designing, manufacturing, and applying pesticides effectively. Different rheological properties can affect how well a pesticide spreads, adheres to surfaces, and transfers to insects, which ultimately impacts its efficacy. Adjusting the rheological properties of pesticide formulations optimises their performance and application.

Getting the rheology (the flow and deformation behaviour) of a pesticide wrong can result in a range of adverse consequences. The key issues pest managers will notice are poor or variable efficacy (and an increase in callbacks!) and spray equipment issues, such as caking and nozzle blockages. The reduced efficacy of products with poor rheology results from the uneven application of insecticide on surfaces, with some areas under treated and others over treated.


What are the signs of a product with poor rheological properties?

Two visual clues indicate poor rheology in a pesticide: firstly, sedimentation in the bottle and secondly, syneresis in the bottle.


What is sedimentation?

Sedimentation, often referred to as ‘hard-pack’, in the context of rheology and pesticide products, refers to the solid particles or components within a pesticide formulation settling at the bottom of the container or tank over time (Figure 1). Keeping in mind that particles of active ingredient are not completely spherical in shape, but rather are jagged and irregularly formed, when these particles fall out of suspension in a poorly formulated product they lock together and become ‘hard-pack’ at the bottom of bottles – being very hard to dislodge and homogenously mix back into the bottle even with vigorous shaking. This separation of solids from the liquid phase is of crucial concern in the formulation and application of pesticides.


Sedimentation in a plastic bottle shown under a microscope
Figure 1: Sedimentation in a generic deltamethrin product


Sedimentation can negatively impact the efficacy of a pesticide because it leads to inconsistent concentrations of active ingredients during application. It can also clog spray equipment, leading to uneven distribution and reduced coverage, which can compromise the overall effectiveness of pest control measures. Managing and minimising sedimentation is a key consideration in developing pesticide formulations and ensuring their reliability in the field.


What is syneresis?

Syneresis refers to the phenomenon of a liquid phase separating or squeezing out from its formulation over time. Visually you will observe a clear layer of liquid form in the top of a pesticide bottle (Figure 2). Syneresis can occur when certain ingredients or additives in the formulation phase separate from the bulk liquid, leading to changes in the product’s rheological properties. This separation can affect the product’s effectiveness and stability. To prevent syneresis in pesticide formulations, careful consideration of ingredients, formulation techniques, and stability testing is necessary. A small layer of syneresis is not of significant concern, however a large layer could be an indication of poor rheology in formulated product.


Unlabelled plastic bottle containing pesticide
Figure 2: An example of ‘syneresis’ in a bottle of deltamethrin from a competitor product. The poor formulation rheology has allowed the product to fall out of suspension. Sundew Solutions’ products are formulated to avoid this


Sundew Transigel Rheology System

Sundew Solutions understands the importance of rheology within its formulations. This is why DeltaPRO 25 Suspension Concentrate Insecticide uses Sundew’s unique proprietary Transigel Rheology System. This innovative technology enhances the product’s performance by optimising its rheological properties. The Transigel system ensures that DeltaPRO maintains its consistency and stability over time, allowing for consistent and precise application. This is crucial when dealing with a wide range of insect pests, as precise coverage is vital for effective pest control.


Sundew DeltaPRO – zero sediment, guaranteed

Sundew’s DeltaPRO’s unique rheology is the secret behind its ability to prevent sediment forming in the bottle. DeltaPRO’s rheological properties are carefully engineered to maintain a stable and homogenous consistency, ensuring that its contents remain evenly distributed throughout its shelf life. Its rheology package prevents any unwanted settling of particles or substances, guaranteeing that DeltaPRO maintains its high quality performance and effectiveness. The product remains in its purest and most potent form until the last drop.

Some generic deltamethrin formulations use cheap gums and fillers in an attempt to keep active ingredients suspended in the bottle. Unfortunately these gums and fillers resist mixing with water when added to a spray tank, resulting in very uneven distribution of active throughout the mix (Figure 3). The quality of treatment using these generic products becomes a problem when larger particles of active ingredient fall out of suspension in the spray tank, resulting in very poor application from start to finish.


Two test tubes side by side
Figure 3: Comparison of a generic deltamethrin product (‘Generic A’) compared with Sundew DeltaPRO 25 SC


In contrast, the Transigel Rheology System in DeltaPRO insecticide creates its ability to spontaneously and homogeneously mix with water upon addition to the spray tank. This rapid and thorough integration ensures that pest management professionals can achieve consistent and uniform solutions, reducing the risk of clogging or uneven distribution in the application process. This feature not only simplifies the handling and application of DeltaPRO but also maximises its efficacy, ensuring that the active ingredients are evenly dispersed for comprehensive and precise coverage, ultimately leading to more effective pest control measures.

The Transigel Rheology System also helps DeltaPRO adhere to various surfaces and substrates, enhancing its efficacy. This feature is invaluable when dealing with insect pests that may hide in cracks, crevices, or on different types of surfaces. The unique rheological properties utilise formulation science from a totally unrelated industry. This makes Sundew DeltaPRO a truly ‘unique’ formulation developed to meet the needs of modern pest managers.

In summary, rheology is a key aspect of product formulation, as the physical properties of a pesticide significantly affect its overall effectiveness. Its importance in product performance drove Sundew Solutions to develop the Transigel Rheology System, which is utilised in DeltaPRO 25 SC, EnsnarePRO 50 SC (indoxacarb) and MaxumPRO 125 SC (beta cyfluthrin). As a result, pest technicians can trust that Sundew products that pour from the bottle will always be as fresh and effective as the day they bought them.


David PriddyChief Executive Officer, Sundew Solutions


Read Part 1 of this series that looks at the role of particle size or Part 2 that explores the importance of plant hygiene in a deltamethrin formulation.

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