Tech Notes Issue 5

Suggestions for Winter Overseeding

If winter overseeding couchgrass with either perennial ryegrass (Lolium perenne) or rough bluegrass (Poa trivialis), the ideal time to overseed is when soil temperatures drop to 21 C. Trinexapacethyl (Primo®) applied 1 to 5 days prior to overseeding enhances establishment of the cool season turfgrass significantly. Topdressing after overseeding promotes good seed/soil contact and research has found that the establishment rate is 50% faster compared to non-topdressed areas.  

Control of Poa annua in both Overseeded and Non-Overseeded Couchgrass: Part II

Successful Poa annua control in both overseeded and nonoverseeded couchgrass is dependent on rate, timing, and application of both preemergent and postemergent herbicides.

Strategies for controlling Poa annua include applying a preemergent herbicide at the time of germination, or waiting until most of the Poa annua has germinated and visible then treat with a postemergent herbicide. In overseeded turf, preemergent herbicide applications are the primary means of controlling Poa annua. With the use of traditional postemergent herbicides applications need to be made 8 to 10 weeks (in the case of prodiamine 10 weeks) prior to overseeding with perennial ryegrass (Lolium perenne). Some of the newer herbicides - sulfonylurea - can be applied closer to overseeding (Always follow labeled instructions and use turfgrass labeled products).

Most failures with the initial pre-emergent application are due to the appropriate rate was not applied, or excessive overlap occurred. In the case of inadequate application rate, potential for Poa annua germination and survival is higher. With regard to overlap, the excessive rate applied
inhibits the overseeded cool season turfgrass species. One method of reducing the risk of overlap is to apply ½ rate in two directions.

In non-overseeded couchgrass turf the pre-emergent herbicide should be timed closer to Poa annua germination in the autumn and then a second treatment, midwinter is recommended where Poa annua infestation is heavy (Again, follow labeled instructions).

Photograph: Poa annua germination in germintaion in overseeded counchgrass turf

Click here to download the article in pdf