Improving the efficacy of biopesticides through novel formulation?

By Dr David Calvert, Co-founder and Director of iFormulate - 23rd April 2019

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Dr David Calvert, Co-founder and Director of iFormulate, explains how formulation techniques are being used to improve the stability, utility and efficacy of biopesticides.
Biopesticides are usually defined as belonging to four classes: microorganisms (bacteria, fungi, viruses), macroorganisms (predators, parasites, nematodes), biochemical or botanical extracts and ‘others’ (e.g. pheromones). Sometimes regarded as a separate sector, there are also biostimulants and plant growth regulators (PGRs).
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In all of these categories (perhaps with the exception of macroorganisms) formulation is often cited as a key enabler in helping improve efficacy. It has been said that a formulation can make or break a biopesticide. As the co-founder of a formulation consultancy, this should be music to my ears, although I do question the implied view that biopesticides are so very different to conventional chemical entities. In fact, there are commercial signs that the worlds of conventional and biopesticides are converging.

Headquartered in Israel, STK’s most well-known product is Timorex Gold, a biofungicide based on a plant extract (Melaleuca alternifolia, often called Tea Tree Oil [TTO]). The company’s most recent product innovation is REGEV, a dual action fungicide with two distinct Fungicide Resistance Action Codes (FRACs). The two fungicides are TTO and difenoconazole. The patent for this technology (WO2013068961) claims that the TTO is delivered in the form of an oil in water emulsion and a number of emulsifiers are claimed. The patent also makes claims for TTO with a large number of fungicides, and hence REGEV could be the first of many new mixtures.
Seed treatments are also an area where biopesticides and conventional pesticides are being formulated together to deliver improved performance. Poncho/VOTiVO – now marketed and sold by BASF – combines the insecticide clothianidin with Bacillus firmus I-1582 in a seed treatment. Clothianidin is absorbed by the roots while the Bacillus forms a barrier around the seed which, it is claimed, protects against up to two generations of pathogenic nematodes.
In these two examples, it is clear that formulation techniques are used to make the active ingredients compatible. However, to make a product suitable for sale it must be stable, both in-can and for sufficient time in the field. This has often been cited as an issue for biopesticides, in particular their UV resistance. So, can this be resolved by formulation science?
In 2016 researchers in Canada encapsulated Bacillus thuringiensis (Bt) spores using a technique called Pickering emulsions.1 The resulting formulations performed better than conventional Bt formulations and was comparable to lambda-cyhalothrin. Interestingly, the materials used were acrylic particles, sunflower oil, iron oxide nanoparticles, ethanol and water, so were relatively innocuous and did not impact the biopesticide’s benign profile.
Similarly, Behle et al in 2010 improved the UV resistance of Beauveria bassiana by the use of feruloylated soy glycerides (FSG), which were subsequently encapsulated in starch.2 The authors also used soluble lignin as a potential spray tank adjuvant to protect against UV. In both cases, the use of environmentally friendly components did not impinge on the benign profile of biopesticides.   
Formulations should also enable an active ingredient to be applied safely and effectively. This is perhaps an area in which there is most progress to be made with biopesticides.
Quite often, it is cited on product labels that biopesticides need to be re-applied frequently and that they should not be applied if rain is to be expected within a certain short timeframe. Whilst this is not uncommon for conventional pesticides, the incorporation of adjuvants such as stickers both in-can and in the spray tank is often a solution to improve rainfastness. I am sure that a number of these are being tried by biopesticide companies, but there should be more mileage and obvious success in this approach. If the existing adjuvants do not bring the desired performance improvement or do not have the required safety profile, then surely this opens opportunities for adjuvant suppliers – perhaps we will have a new category of ‘bio-adjuvants’.
In summary, formulation can be highly significant. Biopesticides are certainly on the up, supported by broad perceptions that they are much better than “nasty” chemical pesticides. Markets and Markets reported global sales of biopesticides of around US$3.0 billion in 2018, growing to US$ 6.4 billion in 2023. This is clearly good growth but, as the total global pesticide market was US$65 billion in 2017 and is growing at 7% CAGR (BCC Research), there is clearly scope for further market share.  However, for biocontrol products to continue their growth, the sector needs more than good formulators. They also need to be adopted into new smart farming practices, and to be defined not just by industry associations but also by regulators.
You can meet David and hear him expand on some of the formulation approaches highlighted in this article at the inaugural Biopesticide Summit in Swansea, UK, on 2–3 July.
Dr David Calvert, Co-founder and Director of iFormulate, UK
M: +44 7860 519582
1. Bashir O et al. PeerJ 2016;4:e2524 (DOI 10.7717/peerj.2524).
2. Behle RW et al. J ASTM Int 2010;8:1–15 (