There are many different recommendations, and it depends on the product. Some product recommends additives, and the most common are non-ionic surfactant (NIS) or crop oils. Some products do not require any additives so it all depends. From my experiences in northern Europe, we will add additives when applying fungicides when dew is on the plant to make sure you get good contact. In general, the best recommendation is just follow the labels, and then go from there. – Palle Pedersen
A drift-retardant type additive should likely be avoided as it increases droplet size, but again, follow the label, and look for guidance there. – Mark Hanna
