As a follow up to last week’s Turf Tip, Poa trivialis control in athletic fields is far more complicated than in lawns. Poa trivialis is a weed because it will go dormant in July or August (perfect timing before the football season), but will regrow from stolons with a vengeance in September. It is also shallow rooted, so it doesn’t hold up to play even if it doesn’t go dormant. Poa trivialis results from seed contamination during the original seeding or during any overseedings. Seed companies have gotten much better at minimizing Poa trivialis contamination, but it is still important to test seedlots prior to overseeding. Be sure to test at least 50 grams and contact Matt Levy at Seed Technology in Marysville OH at 937-644-0088 or Larry Nees at the Offices of the Indiana State Chemist and Seed Commissioner at 765-494-1557 for testing samples. Once Poa trivialis is in a field, it’s difficult to manage especially in late summer and fall use fields. Unfortunately, you can only learn to live with it because we have no selective controls (yet). Your best bet is to overseed aggressively with Kentucky bluegrass when you have 8 or more growing weeks before the season begins or perennial ryegrass if you have less than 8 weeks before play (yes you read that right, I actually recommend perennial ryegrass in this case). This will allow these grasses to replace the Poa trivialis as it thins and goes dormant in July and August. Also insure that N fertility is adequate because Poa trivialis is extremely sensitive to dollar spot, but fungicide applications will likely be needed anyway to extend the life of the Poa trivialis. Realize though that as you add the perennial ryegrass, you’ll have to watch for brown patch, pythium and other diseases, but I still believe perennial ryegrass is a lesser evil than Poa trivialis. If you want to control Poa trivialis, you could spray it with glyphosate after the last game in the fall, and then aggressively dormant seed with Kentucky bluegrass on fields that won’t be used until next fall. There’s no practical control options on fields used both spring and fall. Our work with Monsanto’s sulfosulfuron is extremely promising and it could be available in 2005 as an option. We’ll have more information on this at our Field Day on July 27th and there’s a brand new publication on our web page entitled AY41-W: IDand Control of Annual Bluegrass and Rough Bluegrass in Lawns.