I reviewed the linked "info" with some degree of amusement. Considering that it was issued by an entity with such a broad product-line (ie. Septic Tank Maintenance, Rust Converter, Cleaning Products, Automotive, Vegetable Glycerin, Liquid Fog), the questionable logic behind their recommendation shouldn't surprise me, but it is evident that they don't quite grasp the full range of function(s) offered by the various surfactants - of which there are many (both in type and function).
Certain types of surfactants - particularly those containing d'limonene - actually improve efficacy when targeting submerged plants with certain contact-chemistries (especially mature plants), and also when targeting several algae species. Whether or not they're required, or beneficial, is somewhat subjective and debatable - but to say that a surfactant "defeats the purpose of the product" (for subsurface-treatments) is absolutely incorrect, IMO.
Does the surfactant cause the herbicide to sink better in the water? Or is it just to get the herbicide to penetrate the waxy covering on the stems/leaves of the plant?
This article seems to make it sound like surfactant should NOT be used on submerged weeds, as it will just stay at the surface of the pond?
https://www.sancoind.com/store/en/pond-surfactant
A nonionic surfactant should only be used when one is applying the product on emergent vegetation like Cattails or on submerged vegetation close to the surface of the water like Duckweed. This is due to the nature of surfactants tending to “stick” to vegetation or develop a thin film on the surface of the water. It does not sink into water well, so if one is targeting deeper submerged aquatic weeds, it would actually defeat the purpose of the product by adding the aquatic surfactant to the spray solution.
