Zoysia grass problem

Question: Good morning. After nearly 30 years of having a thick, green zoysia grass front lawn, suddenly this summer it sprouted a number of various weeds, became thin, and turned yellow-brown. I treated it with two applications of BioAdvanced Fungus Control for Lawns but don't see improvement & fear I may have waited too long to do something. Looking around the neighborhood (Catonsville), I see other lawns that seem similar but now don't know if it's the same issue or the start of seasonal browning. Thank you for any insight you may be able to provide.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied September 23, 2024, 1:32 PM EDT
response: Issues aside from a fungal outbreak are more likely, since we rarely see significant disease damage on zoysia in Maryland. Has the lawn been dethatched regularly? Zoysia forms thatch much more extensively than cool-season turf types, and needs to be dethatched every few years to maintain vigor and health. Occasionally, insect pests like sod webworm and chinch bug can also cause dieback in zoysia, though we can't tell from the photos if either is present, as you'd need to dig-down into the thatch (or dead foliage) layer to find them, and they won't be present all year.  Was the lawn irrigated periodically this summer? If not, drought stress may be a primary contributor to browning. Zoysia isn't going dormant quite yet, but the roots may still benefit from watering if the soil is dry enough.  Fungicide use isn't usually needed for zoysia lawns, and no fungicide can cure existing infections; they only help to prevent or suppress future infections by protecting healthy growth. Going forward, you shouldn't need to re-apply any fungicide, though the active ingredient in the product you already used is fairly broad-spectrum.  Is the lawn fertilized each summer? If not, it might not remain as vigorous on its own without occasional nutrient supplementation. Our Lawn Fertilizer Schedule provides guidance about timing and application rates/limits for lawn types, including zoysia.  Miri

responder: The Question Asker Replied September 26, 2024, 11:26 AM EDT
response: Thank you, Miri. I'm glad it's probably not a fungal issue. To be honest, we've never done anything to the lawn apart from mowing; it's always been lush, green and beautiful. We did rake it thoroughly before applying the fungicide so I hope that helps. I appreciate the fertilizer schedule; we'll begin that in May. Does it seem likely the lawn will recover? Sincerely,Lisa  On Mon, Sep 23, 2024 at 1:32 PM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied September 26, 2024, 12:25 PM EDT
response: Hello Lisa,  Thatch build-up in zoysia lawns does need to be addressed to support the short-term and long-term health of the grass, and renting a dethatching machine (or hiring a lawn company to use one) is generally the best option for removing it. Raking alone will probably not suffice, since the thatch layer is on top of the soil surface and interwoven with the grass blades and crowns and needs to be more aggressively pulled up/out. It can be a messy process, but is valuable for maintaining vigorous zoysia lawns. (You don't see it done much, if at all, on fescue lawns because fescue doesn't really form much thatch.)  If the roots and crowns (the main growth point that produces foliage) of the zoysia are still healthy, then recovery is likely. Since it's a warm-season grass and we're nearly at the end of the growing season, though, little or no new growth will be produced until next May/June (more or less).  Miri