AGROCHEMICALS
Figure 3- Data generated using glasshouse method comparing performance with & without a rainfastness adjuvant and rain event
and formulations. Figure 2 shows an example of the type of data generated from this, comparing a control( a contact herbicide, phenmedipham) with no rainfastness additive to one with a development rainfastness material.
The limitation of this method is that it trades many of the real-world variables for more easily controlled ones in order to boost speed and repeatability. This includes factors such as swapping from leaves to synthetic slides, spray nozzles for a pipette and variable rain for a more consistent pump.
This allows for excellent consistency but means the test needs partnering with a more authentic one to get a complete picture of product performance. For us, the partner method is one carried out by our glasshouse team; formulations are sprayed using commercial spray equipment onto representative target plant species and the overall formulation efficacy is evaluated directly.
Short of full-scale field trials, direct glasshouse evaluation is one of the best ways of evaluating the performance of any adjuvant, with much easier control of conditions for consistent results. Analysis techniques vary by species and active MoA, but plant weight, visual assessment and / or photosynthetic efficiency measurements are all potential options.
Figure 3 shows data obtained using a terbuthylazine( herbicide) formulation applied on Ipomoea purpurea plants
( common morning glory, the same family as bindweed) and evaluated by measuring photosynthetic efficiency. The test compared the same herbicide formulation with and without a developmental rainfastness additive to a treatment with no herbicide.
The same test protocol was carried out on samples with and without a rain event to compare efficacy. It is important to note that the measurements are indicating plant health so for this herbicide test, a lower bar indicates better performance as less active has been washed away by the rain event.
Croda focus
Using methods like those described, we have been running a programme of study assessing the enhancement of rainfastness across a wide range of actives. Most recently, the upcoming European synthetic polymer microparticle regulations( often referred to as a‘ microplastics ban’) have reduced the available sticker chemistries substantially, resulting in an upcoming unmet need for the industry.
In response to this, a wide variety of chemistries have been evaluated looking for compliant materials that will still deliver the required performance. These efforts have looked at a range of options including boosting biodegradability of existing materials, functionalising film-formers from the existing range and evaluating materials from other markets that could deliver the right properties to agricultural formulations.
For Croda, the most interesting chemistry being worked on is a class called alkyd resins, a staple in the paints and coatings industry that has so far not seen wide usage in the agricultural industry. The resins are polyesters, which can be 100 % biobased, with the typical components being readily available polyols, dicarboxylic acids and fatty acids. Varying the components and their proportions enables tuning of key polymer physical and chemical properties that affect film formation.
Alkyd chemistry can be delivered as an oil-in-water emulsion system and therefore be readily included into aqueous systems or added directly to the tank before spraying as a standalone adjuvant. This delivery system is then able to provide rain-resistant films to surfaces from aqueous dilutions in a spray tank; thereby affording a solution to the challenge of providing rainresistance( which often necessitates hydrophobic ingredients) from waterbased systems, such as suspension concentrates. This class can be tuned for optimal formulating and rainfastness properties, while being made up of all liquid components to conform to upcoming microparticle legislation.
Conclusion
Rainfastness adjuvants play a vital role in agriculture, helping protect pesticide performance even after rainfall or irrigation.‘ Sticker’ adjuvants are now under increased scrutiny, as upcoming EU microplastic regulations are likely to limit the commercial use of many existing products. In response, we are intensifying our search for alternative, sustainable technologies that meet regulatory expectations while continuing to deliver marketled innovation. ●
Ryan McDonald
APPLICATIONS TEAM LEADER
CRODA k + 44 1405 860551 J agriculture @ croda. com j www. crodaagriculture. com
22 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981