Preemergent/Poa annua applications to Dormant Zoysia

During the month of February or very early March, we apply our preemergent(Ronstar) and non selective weed killer(Round Up Pro) to our Zoysia areas of the golf course; fairways, tees and green surrounds that are solid warm season grass.  We make the application this time of year because the Zoysia grass we are trying to protect is dormant and will not be injured from the spray.  Round Up is safe to use only when warm season turf is dormant.  We wait for temperatures to rise above freezing and sunny days.  The chemical will move more readily through the plant if the conditions are warmer and sunny.

Our first target we are trying to control is any cool season grass, mainly poa annua which has germinated in the fairway/intermediate cut/ tees and green surrounds.  This application will also kill knotweed and will restrict the growth of rye, fescue and blue grass.  If this material is not sprayed out, there will be large clumps of weed grass that seeds profusely and will leave our fairways very clumpy until we begin to mow in late April/early May.


Our second target is to prevent crabgrass and goose grass from germinating in the spring and summer.  We make this combination tank mix to to reduce wasting time and energy of a second application.  This material will lay dormant on the surface of the soil until it is needed in the spring.  This year, we are using Ronstar because it has the least negative activity on the root systems of our warm season grass.  We had great warm season turf last year and I want to continue that push into this year as well.  This material does cost more but it is wise to change chemistry's every few years to reduce the potential for resistance.  We will be using Barricade on our rough areas in late March to early April along with a broad spectrum selective weed killer.

Here's the spray rig after the tank was emptied this morning.  We utilize a soap marking system and some green dye to help outline the areas that we spray.

This picture is along the right side of #18 fairway.  You can see how excessive shade encourages poa annua.  Without the leaves on the trees,  you can still see the affects of the shade.  If the poa was not sprayed, it would begin to choke out the zoysia.  Our trees provide character for the course but also do encourage our poa annua population to explode.