TAM-AAMM
Texas A&M—AgriLife Agronomic Monday Memo (Jan. 20, 2025)
Zach Howard, Extension Program Specialist II, Soil & Crop Sciences, College Station
(979) 321-5928, zachary.howard@ag.tamu.edu
Bearing with Sandburs – Managing a Painful Pest
February is the time for forage and turf managers to begin waging war against this pest.
Many Cenchrus spp. go by grassburs, sandburs, stickerburs, or other names. This genus includes annual and perennial grasses that produce a pain-inflicting seed head. The burs that house the seed not only have spines but have fishhook-like barbs that grip what they have grabbed (Fig. 1).
There are three native species of sandburs in Texas that make up most infestations. These are also referred to as grassbur by many:
- field sandbur – Cenchrus spinifex
- longspine sandbur – Cenchrus longispinus
- southern sandbur – Cenchrus echinatus
Field sandbur causes most of the problems in grass forages. Surveys across East Texas found all seed samples being this species. This species is particularly problematic as it over-winters or perennializes. These perennials produce foliage earlier, more seeds, and will displace more forage than their annual counterparts.
Forages and turf sites are at risk for sandbur infestations in nearly every county in Texas. The first line of defense is ensuring no seed is introduced onto the landscape. These seeds will travel many miles on wildlife, vehicle tires, and will stick in equipment like hay rake tines, baling belts, and shredders. One to three seeds in the sandbur pod will germinate once soil temperatures reach ~52°F and moisture is available. Germination ceases at about 74°F soil temperature. Many forage and turf managers experience two periods of germination, spring and fall, when soil temperatures are in this range. In my experience, most seeds germinating in a growing season do so in the spring. In 7-13 weeks, a seed head forms (Fig. 2).
The next line of defense against this pest is healthy forage that is competitive. Whether in well-managed bermudagrass hayfields or lush grazed natives, many forage managers still encounter an ever-growing sandbur population. The first step to wage war against these is knowing their location and if perennials are present.
Perennial identification is easiest in winter when the plant is dormant. Sandbur carcasses can be found, excavated, and the root area observed for green tissue (Fig 3). Pale green tissue indicates the potential perennial. If found, your management tactics will change once the growing season is underway.
Herbicide Options
Upon late winter for your area, forage and turf managers can apply a pre-emergent herbicide with the active ingredient indaziflam. Working from South to North Texas, the beginning to the end of February is an ideal month for application. Though other products exist and can be effective, research across Texas points to this active ingredient performing the best for forage and turf settings.
Soon (February) for Best Initial Control in Forages
In a perennial warm-season grass forage where no seeded annuals are present, the preferred program is 3 oz./acre of Rezilon applied in 15 gallons per acre of water minimum. After the first hay cutting or major grazing event where the forage canopy is low and open, another application at the same rate should be made. This will ensure enough residual to last through the fall germination period.
Ongoing Control in Forages
If seedlings are found (≤2”) after baling the first hay cutting or major grazing event, Pastora herbicide at 1.25 oz. per acre included with the Rezilon application will be required for post-emerge (existing weeds) control. If perennials have been identified, Pastora will only be expected to provide suppression to these and any plants larger than 2 inches. Glyphosate at 0.4 lbs. acid equivalency per acre will eliminate larger plants and perennials. This acid-equivalent rate translates to 17 oz. per acre of a 3 lbs. acid equivalency per gallon (lb ae/gal), 12.8 oz per acre of a 4 lb. ae/gal, and 11.4 oz per acre of a 4.5 lb. ae/gal product. (If you need help determining which ‘ae’ your product is, contact your Extension agronomy specialist.) For any post-emerge application, medium droplet size should be produced. Forage injury may occur with glyphosate, but damage is likely to be transient if the application is made within 7-10 days of cutting.
Soon (February) for Best Initial Control in Turf
In a perennial warm-season turf setting where no seeded annuals are present, Specticle Flo at 6 oz. per acre (4 milliliters per 1,000 square feet) should be applied in a minimum of 20 gallons per acre of water (0.5 gallon per 1,000 square feet). A repeat application should be made 45-90 days later. Dry formulation, Specticle G, is available and can be used at 125 lbs. per acre (2.9 lbs per 1000 square feet) at each application.
On-going control in Turf
If seedlings, mature plants and/or perennials are found in turf settings, applications of Celsius WG can be effective at 3.7 oz. per acre (2.5 grams per 1,000 square feet). A repeat application 4-6 weeks later may be necessary for larger plants. This application can be made with the second Specticle Flo application.
Additional Information
All underlined titles are live links. Hit ‘Control’ then click to access.
More information for forage managers is in AgriLife Extension’s Grassbur/Sandbur Identification and Management in Pastures and Hayfields publication. Information for turf managers is in the Grassbur/Sandbur Management in Turf publication. For additional weed management information and contacts for weed related issues across Texas, visit our website.
Forage Herbicide Labels
Turf Herbicide Labels
All above links go to labels for each product at CDMS Home. This website has labels for all pesticides. To learn more about this highly valuable website, review (or request) TAM—AAMM, Ready Online Access to All Chemical Labels—www.CDMS.net, July 17, 2023.
Calvin Trostle, Ph.D.
Professor & Extension Agronomist
Texas A&M AgriLife State Hemp & Sunflower Specialist
Dept. of Soil & Crop Sciences
Texas A&M AgriLife Extension Service
Texas A&M AgriLife Research & Extension Center
1102 East Drew Street (FM 1294) / Lubbock, TX 79403-6603
Phone: 806-723-8432 / Cell: 806-777-0247 / Fax: 806-723-8499
ctrostle@ag.tamu.edu
Lubbock A&M AgriLife Center, http://lubbock.tamu.edu (most of my reports & presentations are here)
Crop Testing Program (Varieties & Hybrid Trials for Texas), http://varietytesting.tamu.edu
Texas A&M Univ. Dept. of Soil & Crop Sciences, http://soilcrop.tamu.edu