What are all those yellow dots on the ground?

What are Chris and Silvio spreading all through the rough?

It isn’t a fertilizer, but a herbicide which we call a “pre-emergent”, or a “pre-em". Pre- em’s are a class of pesticide that is applied to kill weeds as they germinate, and must be applied prior to the target weed’s germination. The herbicide creates a barrier at the ground surface that newly emerging weeds must pass through on their way through the soil. As they pass through the barrier, they absorb the herbicide and die. The barrier, unless physically broken (by a divot, aeration, etc) will persist for 4 months, giving control until mid August. If a pre-em is applied after the target weed germinates and emerges, it is too late, and little control is achieved.

Pre –em’s are used for many types of weeds, but our main target is crabgrass and goose grass.

Crabgrass begins to germinate as the soil temperatures reach 55 degrees f, and continues to germinate until the soil temperature cools in the fall. Goose grass needs higher soil temperatures, and normally doesn’t begin to germinate until late May or June, continuing through September.

We determine our application timing two ways – prior to the soil temperature reaching 55 degrees f, and the “count back”. Count back refers to how long we want the barrier to remain, as it will also prevent wanted grasses from germinating. If we plan for fall reseeding, we need to apply the barrier in time that it will be gone (degraded). April through August is 4 months, so it gives us a seeding date of mid August to be safe.

Applying too early does not give control long enough into the summer, and too late doesn’t catch the weeds before germination, and then the barrier lasts past the late summer seeding window, causing yet another problem. Over and over, I will keep stressing one thing, and that is “Timing is everything for everything” … for everything we do!

We use different pre – em’s for different play areas and for different grasses. In a few weeks we will treat the tees and fairways with another product which was developed specifically for the finer turf areas. We will use yet another pre –em for our greens collars. We do not treat greens because pre –ems prune roots, and on greens, we always need every bit of root that is there. If crab grass or goose grass should emerge, we pick it out with a knife!

So that’s what we are doing, and what all those yellow dots are all about!

From the blog of Ken Thompson CGCS, at The Greate Bay Country Club
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