[Research & Development] Creating New Products

Many of the insecticidal products that pest management professionals use today result from the combined efforts of numerous researchers to provide optimum products. Various current liquid insecticidal products may appear similar as concentrates — a clear to opaque material that doesn’t readily reveal how it is made. Knowing more about different formulations can help you choose and implement them more effectively. Designations by letter help distinguish various formulations.

MICROENCAPSULATION. One of the most advanced formulation processes available today is microencapsulation, which provides certain advantages over traditional formulations. Microencapsulation is the process by which liquid droplets of insecticide are surrounded with a coating. Different processes have been developed to achieve this for a variety of products including paints, dyes, vitamins, medications, food additives, food flavorings and pesticides. Microencapsulation has been attempted with a variety of coatings, such as wax, sugar, fat and polymers.

In the 1980s, Syngenta chemists conducted pioneering research into the use of polymers to encapsulate insecticides. This research resulted in a number of important discoveries and patents, including the capsule suspension (CS) formulation represented by Demand® CS. The tiny microcaps in Demand CS are made up of two monomer compounds, cross-linked to form a membrane or cell wall. The thick, spongy under layer provides for structural support, while the thin, dense outer layer acts as a microscopic mesh to control the release of the active held inside. Syngenta chemists learned to calibrate the release rate of the capsules by altering the cross-links in the capsule wall. Where more rapid release is desired, such as in agricultural insecticide products, fewer cross-links allow for fast diffusion. In pest management, where longer residual is needed, there are more cross-links to slow diffusion. The development of this formulation provides advantages in longer residual, less repellency, improved particle distribution and more effective control, due to better pick up and transfer.

PARTICLE SIZE AND DISTRIBUTION. The Demand CS formulation takes a highly active pyrethroid, lambda-cyhalothrin, and puts it inside microcapsules averaging only 10 microns in size (for comparison, a human hair is about 100 microns thick). These microcaps are suspended in a liquid base, which, once applied, evaporates and leaves the capsules behind. When applied at label rates, the resulting distribution of particles on treated surfaces is more than 10,000 per square inch. Unlike EC formulations, which may carry the active into porous materials, an encapsulated product leaves more active ingredient on the surface for contact by crawling and flying pests.

If we could see the surface of commonly treated areas, including painted and unpainted wood, masonry and concrete, and even vinyl siding under very high magnification, there would be hills and valleys like the surface of some alien planet. For this reason, very small particles of less than about five microns may fall into these grooves and cracks and be biologically unavailable for insect pick up. Many unencapsulated formulations have an abundance of very small particles, and also may have a great number of very large particles larger than about 22 microns resulting from agglomeration (the act of gathering into a mass) of ingredients. These larger "globs" also reduce the effective distribution of the insecticide. Microencapsulation allows the particle size distribution to be controlled and become more uniform, giving a better "spread" of particles from treatments.

CONTROL OF INSECTS. Once applied, the microcapsule can work in a variety of ways to control insects and other pests. The active ingredient may migrate outside the capsule over time and be available for direct contact by insects. Demand’s timed-release action means smaller capsules will release the active more quickly, while larger capsules will remain intact. Some larger arthropod pests may break the capsules when walking over them, or ingest capsules when feeding or preening. Capsules also can adhere to the cuticle (due to its liphophilic, or "fat-loving" nature), hairs and appendages of the insect. In this case, the active will diffuse into the body of the insect, causing death a few minutes later.

Microcaps are easy to mix and pose less exposure to the applicator. Research findings suggest clear advantages for microcaps.

The author is a senior technical representative for Syngenta. He can be reached at dkaukeinen@giemedia.com.