Should I use NZLA Etho as a pre-emergent for Poa Annua on my ryegrass this autumn? How does Etho work?

Etho works two ways. As a pre-emergent it sits in the top layer of soil and stops new poa seedlings from establishing, similar to how Blockade works. It also has post-emergent activity on poa that’s already come up, as long as the plant is young. Mature poa becomes increasingly difficult (and slow) to control.

It’s slower on mature poa because the chemistry targets actively dividing cells, root tips, growing points, and expanding leaves. A young, fast-growing plant is producing new cells everywhere, giving the product more to work on. A mature plant with established tissues has far fewer sites of cell division, so whatever gets in has less to disrupt and so it takes much longer to work.

Pre-emergent applications every 2-3 months keep the barrier active. During late autumn when poa pressure peaks you can tighten that to every 6-8 weeks, then pull back through spring. You do need to be careful with resistance with Etho. The last thing you want is poa that is resistant to Etho and that’s pretty common from overuse or not following the correct post-emergent application process.

For established, young poa control the label rate is 40ml per 100m² in 4-5L of water. The first application is watered in with 3-5mm of irrigation straight after, which does two jobs at once. The water carries Etho down into the soil profile where it forms the pre-emergent barrier, stopping any new seedlings from establishing. At the same time, the poa plants that are already up take the product up through their roots and lower stem as it moves through the soil around them. This is the slower, systemic pathway where the product moves into the plant and starts working on those actively dividing tissues from the inside.

Then 7-14 days later you do a repeat application at the same rate, but this time you let the product dry on the foliage. By this point the pre-emergent barrier is already set, so there’s no need to water it in. This application targets the above-ground plant directly. Etho is absorbed through the leaves and growing points, hitting the meristematic tissue from the outside in. It also disrupts the waxy cuticle that the plant uses to regulate moisture and protect itself, which weakens the plant further and helps the product penetrate more effectively.

The two applications essentially attack the plant from both directions, roots and stem from below, leaves and growing points from above, while also locking in the soil barrier against the next flush of seedlings. Not following this process and just spraying every so often as a post-emergent is a fast way to build resistance, or leave people thinking the product doesn’t work.