(By Jared Hoyle, KSU Turfgrass Research and Extension)
Yellow woodsorrel (Oxalis stricta) is a perennial or annual broadleaf weed that has clover-like trifoliate heart shaped leaves. Yellow woodsorrel most commonly spreads by seeds that are contained in a capsule that when it explodes ejects the seeds. It can be confused with clover but has yellow flowers with five petals. You can find this weed in a wide range of soil conditions and can commonly be confused with black medic, birdsfoot trefoil and white clover. A similar species is creeping woodsorrel but it is most commonly found in landscape plantings while yellow woodsorrel is most commonly found in turf.
To control oxalis, herbicides that contain triclopyr and fluroxypyr are very effective.
Herbicides that contain fluroxypyr include;
- Battleship III
- Escalade 2
- Momentum FX2
- Vista XRT
Herbicides that contain triclopyr include;
- 4-Speed XT
- Battleship III
- Chaser 2 amine
- Cool Power
- Momentum FX2
- Three-Way Ester II
- Turflon Ester Ultra
- Turflon II amine
- Triclopyr 4
Always remember a healthy turfgrass stand through proper maintenance is the best weed control and can help minimize oxalis in your turfgrass.
Information from this post if from “Turfgrass Weed Control for Professionals” To get your copy today click here – https://www.bookstore.ksre.ksu.edu/Item.aspx?catId=545&pubId=20239
Always remember to READ THE LABEL for the correct rate, turfgrass tolerance, and specific instructions before application!!!
***Mention of trade names or commercial products in this article is solely for identification purposes and does not imply recommendation or endorsement, nor is criticism implied of similar products not mentioned by Kansas State University.***
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Here in Kansas we see our most severe large patch symptoms in spring, but we can see it in fall, especially if conditions are cool and wet. Here, also, we’ve had pretty good success at suppressing spring symptoms with applications the prior fall.
We at KSU and others have been busy trying to tackle this disease in recent years, especially with the increasing interest in zoysia. For a review of research across the transition zone you can check out this article in Golfdom:
Don’t get overmatched: Dispatch that large patch
Moderate days and cool, dewy nights have increased dollar spot pressure. Check out these photos in our research plots.
Here is an untreated plot:
Here is a cleaner plot:
There are many great tips about fungicides for managing dollar spot starting on page 15 of this document:
In terms of varieties, like other universities, KSU does a lot of screening of new breeding lines and existing cultivars. In our research plots we like to have big blocks of different cultivars for different reasons. In my fungicide trials, often I like to use susceptible varieties to make sure we get strong disease pressure. For other types of studies we like to use more resistant varieties when developing reduced-input integrated management strategies.
Here is an example of two varieties out on one of our research greens. They have not been sprayed, and they are not in use at the moment, but they show the striking differences in susceptibility:
I also noticed a tiny bit of lingering brown patch on our putting green. When we switch more solidly into cool fall weather that should fade into nothing. Ah, fall! Let’s have more nights in the 50’s!
If you squint hard, you’ll see the big brown patch circle among all the dollar spot: