In recent years, the increasingly stringent regulations for conventional pesticides coupled with consumers’ growing preferences to eat organically have expanded the need for “biological pesticides,” or biopesticides, derived from natural materials1. Based on the U.S. Environmental Protection Agency’s (EPA) definition, there are two main groups of biopesticides, including naturally occurring substances known as biochemical pesticides, and microorganisms known as microbial pesticides.
Formulating microorganisms into stable products is particularly challenging due to the delicate nature of these living organisms. Additionally, some microorganisms are ultraviolet (UV) sensitive, requiring extra effort to maintain viability under field conditions. For large-scale production of microorganisms, a process known as industrial fermentation is commonly used. This process generates many side products including toxins, proteins and other metabolites, further increasing the complexity of the biopesticide formulation.
To solve these challenges, pine-based chemistry provider Ingevity continues to innovate and develop high-performing agricultural co-formulants made almost exclusively from renewable resources. The newest line of next generation kraft lignosulfonate dispersants, AltaBio™, is designed specifically for challenging microorganism formulations, including wettable powder (WP), water dispersible granules (WDG) and suspension concentrates (SC).
Compared to Ingevity’s legacy Reax® and Polyfon® kraft dispersants, the company leveraged its unique processing capabilities for improved purity and performance to create the AltaBio dispersant product line. These high-performing dispersants are safe with various microorganism species and offer increased suspensibility and wettability compared to alternative sulfite lignosulfonates and various synthetic dispersants (i.e. naphthalene sulfonate formaldehyde condensate and styrene acrylic-based dispersants).
By combining performance and environmental safety, AltaBio performs efficaciously with the flexibility of minimal application restrictions and superior resistance management potential.
Physical properties for AltaBio offerings
Ingevity’s AltaBio portfolio currently consists of eight product grades, all with high purity levels and low salt content, shown in Table 1.
Table 1. Physical properties of AltaBio product portfolio
To determine the appropriate AltaBio grade for specific formulations, Ingevity recommends formulators consider both the degree of sulfonation (DOS) and molecular weight. The DOS characterizes the extent of sulfonation. For example, AltaBio 40, 50 and 55 products have a high DOS, meaning they are more hydrophilic. Alternatively, AltaBio 60, 150 and 200 products have a low DOS, so they work better with hydrophobic surfaces. Since the main stabilization mechanism for lignosulfonate is steric stabilization, the higher molecular weight results in better steric stabilization. For example, Beauveria bassiana is known to be very hydrophobic and difficult to suspend in water. AltaBio 200 would excel in that specific formulation due to its low DOS and high molecular weight, providing increased affinity to the hydrophobic surfaces and strong steric stabilization for long-term formulation stability.
Among the eight available products, AltaBio 40, 60, 4082W and 6082W are included on the U.S. EPA’s 4B list for organic pesticide formulations.
AltaBio 4082W and AltaBio 6082W have built-in wetting agents and can be used to wet hydrophobic spores without the need of an additional wetting agent (see Figure 1).
Figure 1. AltaBio 4082W provides excellent wetting to hydrophobic Beauveria bassiana spores.
Environmental safety and UV protection
Unlike synthetic naphthalene sulfonate formaldehyde condensate (NSF) based dispersants, AltaBio derived from sustainable processes making it safe to use with various microorganisms, including Burkholderia cepacian, Rhizobium leguminosarum, Bacillus megaterium, Trichoderma reesei, Bacillus thuringiensis, Bacillus subtilis, Beauveria bassiana. As shown in Figure 2, no zone of inhibition was observed on a lawn of microbes treated with AtlaBio products, while the NSF-based dispersant showed a clear zone of inhibition when incubated with Bacillus thuringiensis.
Figure 2. Inhibition tests of AltaBio products and a NSF-based dispersant on Beauveria bassiana and Bacillus thuringiensis.
Specific bacteria, fungi and viruses can provide effective pest control when sprayed onto plants. However, these microbes are rapidly degraded by sunlight, which limits their field efficacy. AltaBio combats the degradation by providing additional UV protection to various biological spores, such as Bacillus megaterium, seen in Figure 3. However, since it is a highly active dependent, the UV protection must be further evaluated for use in other biological species.
Figure 3. UV protection of AltaBio to Bacillus megaterium.
AltaBio outperforms alternative dispersants for Beauveria bassiana
To compare the performance of AltaBio to alternative dispersants, the challenging biological active Beauveria bassiana was formulated into WP using various dispersants including three Ingevity kraft lignosulfonates (AltaBio 200, PolyFon F and Reax 910), two naphthalene sulfonate formaldehyde condensates, a styrene acrylic-based dispersant, and two sulfite lignosulfonate dispersants. The detailed recipe is shown in Table 2.
Table 2. Beauveria bassiana WP (10%) formulation recipe
The WP formulations were dispersed thoroughly in water, then particle size and suspensibility of each formulation were measured.
Compared to other dispersants, two formulations that contained kraft lignosulfonates resulted in smaller particle size of D50, and less conidia aggregates, as shown by D90. The smaller particle size at D50 and less aggregation suggest improved coverage of AltaBio on the conidia surface, resulting in higher suspensibility of the formulation at 86.4%. Additionally, when compared within the kraft lignosulfonate group, higher MW dispersants perform better than the lower MW counterpart. This observation proposes steric hindrance as one of the stabilize mechanism in these formulations.
Table 3. Properties of Beauveria bassiana WP formulations with different dispersant
*Overestimated suspensibility value observed here likely resulted from higher quantity of unwetted conidia floating on the suspension surface.
AltaBio 200 performance in Beauveria bassiana WDG formulation
Based on the prescreening result detailed above, Beauveria bassiana WDG was successfully prepared using AltaBio 200 with detailed recipe shown in Table 4.
Table 4. Beauveria bassiana WDG formulation recipe
Figure 4. Beauveria bassiana WDG appearance.
The formulation above produces porous granules that disintegrate easily in water and provide suspension with small particle size ~4µm at D50 and ~17µm at D90. The small particle size at D50 and D90 indicate very minimal conidia aggregation upon water dispersion.
The WDG formulation proved to be very stable when subjected to freeze/thaw conditions, as shown by the preserved disintegration property with small particle size growth to ~4.5µm at D50 and ~20µm at D90.
Figure 5. Beauveria bassiana WDG upon wetted in water (left). Beauveria bassiana WDG dispersed in water (1%) after 30 minutes left undisturbed (right).
Achieve high performing formulations with Ingevity’s ultrapure dispersant, AltaBio
With ultrahigh purity and enhanced molecular weight, AltaBio provides excellent coverage for microbiological actives, leading to high-performing WP and WDG formulations. With more than 90% bio-derived content, AltaBio has excellent safety, suspensibility and wettability properties and prove to be extremely safe with various microorganisms.
Ingevity’s agrochemicals technical team can help customers utilize the key advantages of these co-formulants by offering confidential, complimentary co-development of difficult formulations. Through ongoing technical support and seminars, Ingevity can share new data and advice for formulating with dispersants, adjuvants, solvents and other co-formulants.
1. Transparency Market Research; Biopesticides Global Industry Analysis, Value, Share, Growth, Trends, and Forecast Report, 2019 – 2027; https://www.transparencymarketresearch.com/report-toc/116.
This article will be published in AgroPages '2021 Biologicals Special' magazine to be published this June.
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