Can you spray Etho on a dewy lawn in the morning?
Looking at doing a application of Etho this morning but lawn has dew on it, is that ok to apply?
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Depends which step of the two-step process you're at. If it's the pre-em application (the first one), you're watering it in straight after anyway, so a bit of dew on the leaf doesn't matter. The product's going down into the soil to form the barrier and the dew gets washed in with the rest of it.
If it's the second application (14-21 days later) as a post-em on poa, the leaf surface does need to be dry. The product needs to sit on the foliage and absorb in, and excess moisture (whether it's dew or rain) washes some of it off and slows uptake. So a heavy dew on a post-em application isn't ideal.
There's a real resistance issue with this product. Poa annua resistance to ethofumesate is well known, and the way to drive it is by using the product wrong, one-off applications without watering in the first application and following up with a post-em application is how you get resistance, particularly when dealing with mature poa.
Even when you do follow the two step process correctly, Etho is slow to work on poa. It causes growth abnormalities that eventually kill the plant, but that takes time. On mature poa with slow growth this time of year, the chemistry has even less to disrupt because the plant isn't doing much so it's essential to follow the two step process.
Randomly applying as a post-em application, particularly on mature poa is a quick road to resistance.