Rainfastness.

It looks like we may see showers throughout the month of May.  How does that affect agrochemical application?  What are we talking about when we say “rainfastness”?

Rainfastness refers to a crop protection product’s ability to maintain performance after exposure to rain or irrigation which is particularly important during showery weather conditions.

Why? Simply because once applied the product needs to hit the leaf surface and then remain there long enough to perform the task for which it was applied. 

Many products are formulated with additives and require minimal time after application to perform their intended task.  Rainfastness additives are ingredients that maintain efficacy after a rainfall event.  Their modes of action varies.  Some reduce wash-off, others improves how the formulation spreads across the leaf surface whilst others improve adhesion.

Trisiloxane adjuvants can improve rainfastness by providing “super-spreader” properties within a formulation. As highly effective wetting agents, they allow the spray solution to spread quickly and evenly across the leaf surface. This accelerates the drying process, helping to reduce the risk of wash-off from rainfall.

Uptake enhancers increase the rate and amount of active ingredient absorbed into the leaf. They are highly effective for systemic actives that need to cross the leaf cuticle to be effective. Once the active ingredient has entered the leaf, it is protected from being washed off by rainfall.

Stickers are chemicals that form a protective film on the leaf surface. This film is resistant to environmental factors such as rain, irrigation, and humidity. They are also generally compatible with a wide range of active ingredients.