Turf - Brown Turf Areas in Spring

You may still be seeing brown areas in lawns that have greened up this spring. These are places where warm season grasses were dominant last year. The following is an article on the subject.

Cool season turfgrasses have greened up across the state. However, there will often be distinct areas of turf that remain brown or straw colored. These are areas where warm season weeds died out or went dormant last fall. It is important to take note of these areas and determine what control measures will be necessary this season. Crabgrass is the most common weed that winter kills leaving large browned out areas. Goosegrass could also be the culprit, especially in compact areas. Crabgrass and goosegrass are annual species that will come back from seed. Crabgrass is germinating in turf now, goosegrass will be germinating as we go into May. If you have missed the timing for crabgrass preemergence applications, dithiopyr (Dimension) is an option now as it has both preemergence and early postemergence activity on crabgrass. However, it is not safe for areas that have been or will be seeded this spring. For new seedings, quinclorac (Drive) would be the best option as a postemergence herbicide once all the crabgrass has germinated (May). Quinclorac will not control goosegrass.

Brown areas may be patches where perennial warm season grasses grew last year. These grasses will begin to regrow again in May. Bermudagrass (or wiregrass) is the most common warm season perennial grass weed that appears brown in dormancy throughout the state. Zoysiagrass is possible but usually restricted to areas near to where it was planted. Another possibility commonly found in Delaware is nimblewill which will appear as fuzzy looking patches. Both Bermudagrass and zoysiagrass spread by underground rhizomes whereas nimblewill does not. Control of these three perennial warm season grasses is difficult. Total renovation with several applications of glyphosate herbicide is often needed. Post emergence suppression of Bermudagrass can be accomplished with multiple applications of fenoxaprop (Acclaim Extra) in tall fescue turf.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Turf - Brown Grass Areas

Brown grass areas this time of year in cool season turf are commonly because of undesirable species and weeds that have gone dormant or have been killed by frost. The following are common problem weeds in lawns that brown out this time of year.

• Bermudagrass, also called wiregrass, will be going winter dormant this time of year leaving straw colored areas in lawns. Zoysiagrass and other warm season perennial grasses will also go winter dormant.
• Nimblewill is a common perennial grass weed that will go winter dormant this time of year.
• Annual grass weeds such as crabgrass and goosegrass are killed by frosts and straw colored areas will be seen where they were heavy.

Dormant burmudagrass is turning straw colored in turf areas now.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Turf and Landscape - Nimblewill

Nimblewill is often confused with Bermudagrass in turf because it has a similar appearance but is more common in shaded areas. The following is information on this weed.

Nimblewill, Muhlenbergia schreberi, is a warm season perennial grass that is a common summer weed in older established turf. It proliferates in moist, shady areas, but also can be found in full sun, especially where there is irrigation. Nimblewill has thin stems that can root at the nodes when touching the ground and forms dense mats. It also spreads by seeds that are produced in late summer. It is similar in appearance to common bermudagrass (wiregrass) in that it has small leaves and is wiry in appearance; however, it can be distinguished by the lack of rhizomes or true stolons and by having a short, membranous ligule (bermudagrass has a hair-like ligule).

Control of nimblewill in landscape beds is accomplished by post-emergence applications of grass herbicides: sethoxidim (Vantage), fluazifop-P-butyl (Ornamec, Fusilade II), and clethodim (Envoy plus). In cool season turf there are no good selective herbicides currently available. Hand digging or use of non-selective herbicides such as glyphosate followed by reseeding or sodding is the recommended control. A new herbicide, mesotrione (Tenacity), is very effective on nimblewill in cool season turf but is only labeled for golf courses and sod farms currently. It will be the standard for control in other turf situations if and when available in the future.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.

Turf - Tenacity Herbicide (Mesotrione) for the Control of Bentgrass and Nimblewill in Cool Season Turf

Tenacity herbicide with the active ingredient mesotrione will give control of bentgrass and nimblewill in cool season turfgrass. The following are some slides on these uses. Currently Tenacity is only labeled on golf courses and sod farms.

From a presentation by Dr. Steve Hart, Rutgers University

Ornamentals Hotline Weed Pictures for Issue 19, August 3, 2007

White clover, an indicator of low mowing height and low fertility soil.

Spurge, an indicator of compacted soil.

Prostrate knotweed, an indicator of compaction.

Red Sorrel, an indicator of low pH, low fertility soil or dry soil.

Plantain, an indicator of low fertility soil.

Nutsedge and Oxalis (woodsorrel), indicators of wet soil.

Nimblewill, an indicator of excess shade.

Goosegrass, an indicator of compacted soil.

Crabgrass, an indicator of low mower height, wet soils, or high fertility.

Carpetweed, an indicator of dry soil.

Black Medic, an indicator of dry soil.

Bermudagrass (wiregrass), an indicator of low mowing height, compaction, or high fertility.

All Weed Pictures by Gordon Johnson, Extension Agent, Agriculture and Commercial Horticulture, University of Delaware, Kent County