Wednesday, March 22, 2023
HomePasture HealthForageNew Brush Control Philosophy Works for Ranchers

New Brush Control Philosophy Works for Ranchers

This article first appeared in the 2015 Proceedings of the 6th National Conference on Grazing Lands held in Dallas last December.

“As land managers, if we focus on dealing with problems we will continue dealing with problems. If we focus on our desired objectives and visualize what it takes to achieve that objective, then we can get it done.”

This is a paraphrasing of John “Chip” Merrill on achieving ranch objectives.

gulf-coast-prairie-regionSeveral Ranchers in the Gulf Coast Prairie Region have come to realize that we have been focusing on the brush problem rather than focusing on their common objective which is to grow more high quality native vegetation, both forbs and grasses. The invasive brush problem has become a losing battle as huisache has replaced mesquite as the dominant brush species. Once huisache becomes established on the landscape it soon dominated the landscape unless immediate steps were taken to keep this brush species under control. The ranchers in this group communicate with others in the group concerning their efforts for brush control containment. They share information on methods that work better than others, chemicals, treatment timing and treatment costs. They also communicate options that eliminate the treatments that are least effective.

From a treatment standpoint, once a canopy density of 15 percent is passed, it becomes a very difficult struggle to keep huisache in check. When the canopy reaches 30 percent, the reduction of sunlight reaching the ground cover causes about a 30 percent reduction in forage production. Prescribed burning is one of the important tools used to maintain a lower canopy cover.
Burning is usually the most cost effective method to keeping huisache under control. Burning seems to kill most of the one and two year old seedlings but the 3 year old and older plants resprout from the root after being burned. As the huisache canopy increases it becomes very difficult to grow enough grass fuel under the huisache canopy to carry out an effective prescribed burn. Burning requires rather precise weather conditions for a successful burn. Oftentimes weather conditions will not occur at the right time and the opportunity to burn is missed.

Example of huisache overgrowth in pasture. Photo from Texas AgriLife.
Example of huisache overgrowth in pasture. Photo from Texas AgriLife.

In most of the dense canopy huisache brush pastures plant counts almost always exceed 450 plants per acre. This type of dense canopy provides little to no grazing for cattle, not enough grass to carry out a prescribed burn, little to no food for deer. Prairie birds such as quail and turkey avoid these areas and wildlife in general finds only escape cover in these areas. When a pasture gets a dense brush canopy of (450 plus plants per acre) with taller huisache and mesquite, the only effective treatment is aerial spraying with a herbicide. In the last 15 years, huisache canopy cover in this region has increased at least 60 percent.

The group of about eight Ranchers mentioned above focused on the “problem” for a number of years. In the last 3 years the group has changed their focus to the objective of increasing native grass and forb production. Rather than a goal to kill the brush, the main goal for this group has become one of meeting the overall objective using a 3-year chemical systems approach. A Chemical “system approach” is the use of a foliar chemical treatment that may kill as little as 25 to 35 percent of the brush plants the first year. After the brush is sprayed the brush plant is defoliated or top killed. When this happens, soil nutrients, soil moisture and sunlight become available to the grass and forbs under the dense brush canopy. When the dense brush is sprayed in the fall, the newly released sunlight, nutrients and soil moisture create an unusually high volume of new fall plant growth. This new grass growth continues during the spring until the plants not killed by the spray regain or resprout new leaves and the canopy closes again in the summer. Best results from this systems method occur when this method is used for 3 consecutive years in a row.

A spraying the first year only kills about 30 percent of the plants, but if this treatment is used a second time the following year, 40 percent of the living plants are killed. The third consecutive year will result in a 50 percent kill on the remaining plants. If an area has a tall dense canopy of brush that has a plant count of 450 plants per acre, the first treatment kills 30% or 135 plants leaving 315 plants per acre. The second year the spray will kill 40 percent of the living plants or 126 plants leaving 189 plants per acre. The third year with the system spray will kill about 50 percent of the remaining live plants. This kills 94 plants leaving 95 plants per acre. When the plant count gets below 100 plants per acre, the preferred and economical method to kill the remaining brush species then becomes individual plant treatment or IPT.

When this system method is used the first year aerial spraying with the system mix cost $22 per acre. Vegetative clippings were made on the area the first of May and resulted in a production of primarily grass under the sprayed area of 6,000 pounds of dry weight grass per acre. This was in a year of above average spring rainfall. The treated area was about 100 acres in size. An Animal Unit Month (AUM) of forage is 900 pounds of forage. The harvest efficiency of forage utilization by cattle is about 25 percent. Therefore 6,000 pounds of forage become 1500 pounds of forage that can be consumed by a cow. This converts to 1.7 AUMs per acre of additional forage. The 100 acre treated area then produces 170 additional AUMs of grazing. For this ranch 1 AUM has a forage value of $12. The spraying cost is $2,200 for the first year. The added value of the additional forage is ($12 X 170 AUMs) = $2040.

The second year aerial spraying with a reduced herbicide concentration will cost $17.50 per acre or $1,750 for the 100 acres that is re-treated. With normal rainfall the same reduction in canopy for the entire year will produce about 5,000 pounds per acre of forage. With a 25 percent harvest efficiency the area produces 1,250 pounds per acre of forage. This is 1.4 additional AUMs per acre or 140 additional AUMs on the area. With a value of $12 per AUM the value of this additional forage is $1,680. The third year of the system spray mix will again cost $17.50 and will result in a 50 percent kill. The cost for spraying the 100 acres a third time in three years will be $1,750. After the third spraying the 95 plants remaining will be mostly resprouts from plants with dead tops. This low sparse canopy will have almost meaningless grass shading and moisture extracting capabilities. With the rotational grazing system being used and no brush competition forage composition will be very close to the potential maximum production of 7,000 pounds per acre. Again using 25 percent harvest efficiency this produces 1,750 pounds of usable forage or 1.9 AUMs per acre. The 190 AUMs has a value of $2,280.

The three-year cost using the system aerial spraying cost for the 100 acre treated area amounts to $2200 + $1750 + $1750 for a total of $5,700. The added value of the spraying has a total 3-year value of $2,040 + $1,680 + $2,280 for a total of $6,000. The fourth year will hopefully have a prescribed burn to remove most of the dead trees and shrubs. If burning is not an option because of the weather, then IPT foliar spraying will be used where the expected kill rate will be 90 to 95 percent on the regrowth.

Huisache is pretty in moderation.
Huisache is pretty in moderation.

This new approach that tries to optimize grass or forage production also results in getting the brush canopy cover to 10 percent or less at about a break even cost / benefit ratio at the end of three years. The Ranchers involved in this on-going project are committed to making this work. This project takes time and commitment to the brush control task each year. Each of the 3 aerial sprayings reduces the carbohydrates in the root system of the plant. After the second spraying, the root system of the brush begins to die back to what the aboveground foliage can support. When we keep the foliage growth to no more than 5 percent, root damage to the brush plant is almost fatal. Failure to do the follow-up treatment the second and third years will cause an unknown amount of damage to the system by allowing some root recovery. It will add an unknown amount of additional cost to the process, and wreck the timetable for finishing the project. Completing the three year process regains the Coastal prairie ecosystem, and greatly enhances Coastal Prairie wildlife habitat. This new focus on the objective of growing a more diverse and ecologically sound community of plants achieves our “objectives” and it removes our initial “problem.”

natglc-logo-1Thanks to the National Grazing Lands Coalition for making this article possible. Click on over to see the great work they do for all of us. Thank them for supporting On Pasture by liking their facebook page.











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  1. The most important part of this received very little attention. It will be the grazing method that will keep the brush in check.
    The ranchers need to study other projects before implementing a grazing plan.
    Most likely it will require severe grazing at certain times, than full recovery of the beneficial grasses before hitting it hard again. Small paddocks with a lot of ground disturbance should be considered.

  2. I wonder if root plowing or dozing (if the huisache is to big) would be a better alternative? Treating it chemically you will still have the dead plants taking up valuable space.

    • and a lot of good, hard wood for the next range fire unless removed. I know goats will eat some. Best bet is always to hit it when in bloom, goats or spraying. The plant is already stressed making blooms, and then it has to try to come back and rebloom before summer hits it. Works with mesquite, I’m told, if livestock are trained to eat it.

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