Golf Course Maintenance Weekly 7/21/16

Summer Weeds

Much has been written about summer being the hardest time of the year for the turf here at Granite Bay Golf Club. In addition to the heat and long days of summer being hard on the cool season turf that encompasses most of the course, these summer conditions facilitate every type of pest as well. Disease, insects and weeds all prosper when the weather gets hot. Therefore our task to maintain healthy cool season turf in the summer goes beyond managing irrigation and into prevention of disease, insects and annual weeds but reacting and pushing back on perennial weeds. 

Crabgrass near #10. Crabgrass is the easiest type of weed to control because we actually prevent it from germinating. It is an annual weed therefore applying pre-emergent products at the proper time prevents the weed from ever getting established. Above recent picture at GB is an example of an area where the pre-emergent product was missed.

Annual weeds such as crabgrass are much easier to prevent so are not as much of a problem as perennial weeds. Annual weeds emerge from the seed they produced the previous year(s). Pre emergent products that prevent the weed from germinating, establishing and producing seed interrupts the cycle and keeps that pest problem in check. 

Perennial weeds return every year from both seed and root and stem system's that have overwintered. If they are not prevented or eradicated their spread will just continue. Preventing and eradicating is easier said then done with some of the weeds we that have taken a foothold here at Granite Bay. A picture is worth a thousand words so below are some illustrations of the various weed issues and control strategies for those who are interested.

Dallas Grass (paspalum dilatatum)

Dallas grass is one of the most obnoxious weeds and difficult to control as it is a perennial weed that comes back year after year from it's roots. Isolated patches like this it is almost easier to dig it out. There are selective herbicides           ( products that hurt the weed but not the desirable turf)   that can eradicate this nasty weed but you have to remain diligent.

Dallas grass in a bunker finger on #12.
We will just dig these out and hope we get all of the roots.

Dallas grass near creek on #16.
This area has become so inundated that we will have to treat with a non-selective herbicide ( products that kill whatever they are applied to. Most common non selective herbicide is Round-Up ) or be diligent with selective products that are marginally effective.  When selective products are used in a aggressive manner, which means frequent re-application's, we have been able to push the encroachment back.

 Dallas Grass in the bank directly in front of #16 green and the fairway side of the creek where we have treated with selective products on multiple occasions  and multiple years. We are gaining a little bit of ground but mostly just pushing it back and not losing ground.

Knotgrass (paspalum distichum L)

Untreated knot grass in #18 FW.
Knot grass is another perennial weed that has the potential to be even more of a problem for us then Dallas Grass in that it has started to infiltrate the playing surfaces. The most successful strategy to date is using the same limited selective product that we use for Dallas Grass remaining diligent on reapplications while it is actively growing. we have not eradicated the problem as effective selective products just don't exist at the present time but we have been successful in mitigating and pushing the problem back

Knot Grass in the process of selective control.

Closeup

Example of slight discoloration of the desirable grass while using selective products to control knotgrass in #9 FW

A few years back we attempted the non-selective approach of controlling Knot Grass in #9FW. After the knotgrass was dead along with all surrounding desirable grass we seeded and topdressed. 

The following year we still had Knot Grass reemerging in the areas we had seeded. Needless to say the non selective approach of eradication was scrapped.

Nutsedge (cyperus rotundus L)

Nutsedge bunker finger #9
Nutsedge is another perennial weed we have to deal with here at Granite Bay. The good news for this weed is we have been able to keep it in check with a different selective product then we use for Dallas Grass and Knot Grass. This particular product is very effective for the selective control of Nutsedge therefore the infestation has never gotten  out of hand.

Yellow Nutsedge patch in the approach of #16

Conclusion

Weed control and prevention will always be something we will deal with in one way or another here at Granite Bay and most of the heavy lifting will occur in the summer months when the perennial weeds are actively growing. Until a effective selective product is available for control and eradication of Dallas Grass and Knot Grass we will have to rely on old school chemistry for control which currently does not  completely eradicate the weeds but keeps them pushed back.