D. M. Kopec, Extension Turfgrass Specialist
Come September and early October, it is overseed time again. This is the time honored ritual of semi-demolishing everything we did last summer to get rid of the ryegrass, and bring back the bermudagrass. Luckily, we had a hot spring this year, and transition should have been easier than previous years.
With the preparation for overseed, there is always the concern for Poa invasion, which is a rite of passage. There are some options you have, and all is not lost.
For overseeded areas (except greens):
Rubigan (fenarimel) is a unique product. Normally used as a fungicide, it has been also used as a pre-emergence for Poa for about 20 years now. Follow label directions for selecting either the three application program (4 ounces/product/1000 square feet) or the two application program (6 ounces/product/1000 square feet). If the overseed contains roughstalk bluegrass (otherwise known as Poa trivialis) then you may favor the three application program.
BARRICADE (active ingredient is prodiamine) is in its second full year of use as a pre-emergence for Poa control in conjunction with overseeding.
BARRICADE is in the same chemical family of pre-emergence chemicals that include surflan, treflan, benefin, and pendimethalin. These are effective grass inhibitors. The rate and timing of applications are very critical for preventing Poa germination, and yet, not affecting the ryegrass.
When applying BARRICADE, make sure you overlap with the spray boom correctly. Always use, a spray marker and indicator.
Rate and timing application options are as follows: (Note that BARRICADE is a 65 WDG formulation.)
1. 6-8 weeks before overseeing, apply 5/8 to 1.0 lb. of product/acre. (This is the same as 0.40 lbs. to 0.65 lbs. of active ingredient per acre.)
Make sure that you do not exceed the label rate, and do not cause "double rates" from improper spray overlaps. Make sure you are six weeks or longer away from overseeding.
2. A second (post-emergence to ryegrass) application is also listed on the label. This application is to be timed after the ryegrass has been mowed several times and the roots are at least two inches in the soil. This application is intended to control the remaining Poa that would theoretically germinate later. Fertilize your overseed adequately to get good root growth early!
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.