One of the more challenging weed species to control in this part of the state has historically been sandburs. Sandburs are found throughout the state and are a common weed of pastures, ditches, vacant lots, lawns with a lot of weeds, and areas of disturbed soils.
When mature the plant's inflorescence (seed head or flowering part of the grass) contains a cluster of burs (hence the name) each containing between 8 and 40 spines and 1 to 3 seeds.
The spiny nature of the bur helps the plant to distribute itself into new territory by hitching a ride on unwilling hosts. The spiny nature of the bur also keeps it from being heavily grazed by livestock and greatly diminishes its value as a forage crop.
Sandburs in East Texas typically mature and produce burs from mid-summer into fall. Mowing sandbur plants repeatedly will cause them to spread more horizontally rather than vertically in order to allow them to produce their seed crop.
Sandburs are pretty easy to identify when they are mature and full of burs; however, bermudagrass pasture managers have a new chemical tool available that will enable them to gain the upper hand in the battle against the bur, but the key is early identification and spraying of this plant pest.
Dupont chemical company has received a Section 18 emergency use exemption for the use of their new pasture herbicide called Pastora in bermudagrass pastures from the Texas Department of Agriculture. Pastora is a restricted use pesticide in Texas and can only be purchased and applied by persons with Texas Department of Agriculture pesticide licenses.
The key to good control with Pastora, according to Dr. Paul Baumann, Texas AgriLife Extension Service weed specialist, is to apply it to bermudagrass stands when sandburs are less than 1.5 inches tall. In order to ensure that the product comes in contact with the sandburs, the label also specifies that the bermudagrass should be 4 inches tall or less (so application following the first hay cutting may be a good option). Applying to sandburs taller than 1.5 inches, the label states, may result in suppression of the plants and may result in a reduction of seed heads.
This product is not labeled for use in pastures with desirable bahiagrass. An application of Pastora may temporarily yellow or delay growth in a bermudagrass field. Pursuant to the Section 18 exemption, producers must be in possession of the Pastora label when making the application.
In order to assist producers in identifying seedling sandburs, Dr. Baumann has developed an identification guide that shows sandburs at various stages of growth from seedling to mature. The plant has somewhat flattened stems which are often purplish in color at the base. It is sometimes possible to dig up suspected sandbur seedlings and find a bur still attached to the roots.
A copy of the Pastora Section 18 label as well as Dr. Baumann's identification guide can be found below.
Sandbur (Grassbur) identificaion guide sheet: Grassbur.pdf
Pastora Herbicide Section 18 Label for Texas: PastoraSection18LabelTexas.pdf