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.
@Jonny Hicks donyou have an article with the best time of the year for Etho applications for both pre and post emerge
@Sam It’s actually quite a difficult one to answer, but I’d always say that prevention is better than cure when it comes to Poa annua. Preventing it is much easier than trying to control it after germination, mainly because of how slowly post-emergent control works.
Personally, I focus on maintaining a pre-emergent barrier in the soil heading into peak germination periods. I’ll typically apply a pre-emergent in autumn and then continue with applications roughly monthly through autumn to keep that barrier active. By around September, I’ll put down my last monthly application and then move to a maintenance schedule of every 2–3 months through the growing season.
As a post-emergent treatment, timing becomes more complicated. Poa annua generally germinates and grows through winter when turf growth is slower, which means post-emergent herbicides also tend to work more slowly. If you’re relying on post-emergent control, September is usually when you start to see the best results as growth begins to pick up. However, by that stage, warmer temperatures are also helping the Poa naturally decline due to its relatively shallow, fibrous root system.
So while post-emergent applications can certainly help, my preference is always to stay ahead of it with a preventative programme rather than trying to chase it after it’s already established.
@Jonny Hicks great information. Thinking about the irrigation of 5ml. What affect does rain have on this? I.e we have 16ml forcast in next 3 days. Do I need a dry window and if so how long so the pre em etho stays at the right soil depth.
Awesome thanks!