Crop Profile for Pasture and Rangelands in Oklahoma

• In the entire United States, 491,045,004 acres or 52.7% of the land were considered pasture. Half of this pastureland is concentrated in the mountain (AZ, CO, ID, MT, NV, NM, UT, and WY) and southern plains (OK, TX) regions.

• As of 1997, 49.78% of Oklahoma’s land or 21,882,471 acres were used for range and pastureland making it the single largest use of land in the state.

• In 2000 51% of the native and improved grassland pastures were only grazed, 28% were hayed and grazed, and 15% hayed only.

• The primary animals used for grazing are beef cattle, stockers, horses, dairy cattle, sheep, and goats.

• The most common packaging used for hay in 2000 was large round bales (84.25%), followed by square bales (35.77%), and large square bales (5.58%). (Totals are over 100% because some producers use multiple packaging methods.)

• The average value of pasture in Oklahoma in 2002 was $460/acre, an increase of 6% over 2001. The average rent for pasture in 2001 was $8.50, an increase of $0.20 from 2001.

The following is a map showing the percentage of land area per county that is in pasture.

Insect pests are not usually treated for in Oklahoma Pasture and Range. Only when there is a very large outbreak of insects will producers treat pasture and range land with insecticides. Most of the time treatments for insects is not cost efficient. Sometimes treatment to pasture and rangeland may not be to save the grass but to reduce pest pressure to cattle such as fire ants.

Fire ants can be an irritant to cattle as they feed. Fire ants are mostly a problem in southern counties along the Texas border. Fire ants could become more of a problem for cattle producers in the rest of the state in the future as they migrate north.

Grasshopper control is difficult to judge whether it is economically justifiable. Control is best achieved from May through July 1. Adults are almost impossible to control. In rangeland, control is not justified unless numbers exceed 12-16 per square yard. It works by interfering with the molting process of the immature grasshopper and must be ingested by the nymph to work. It will not work on adults. Dimilin 2L can be used in rangeland, pasture and improved pasture to control grasshoppers. In rangeland, it can be applied as a Reduced Agent and Area Treatment (RAAT). This involves applying it as a strip spray, with coverage ranging from 50 to 90%. Dimilin 2L is registered for use on pasture and improved pasture at slightly higher rates, but RAAT applications are not recommended because 100% coverage levels are required for the rapid growth of the foliage.

Pasture:

Rangeland:

According to a 2000 survey producers used several different types of weed control. Producers used burning to control weeds in all types of grasses, but it was most common in lovegrass and native rangeland. Sixteen percent of lovegrass acres were burned, and nine percent of native rangeland acres were burned. Producers who did burn their native rangeland burned more per producer, at an average of 396 acres. Prescribed burns can be helpful in brush control for pastures and rangeland. Prescribed fires also help with Eastern Red Cedar control which has become a major problem in Oklahoma rangeland.

Brush hogging or mowing was used regularly in native rangeland and some improved pastures. The most common improved pastures using mowing were fescue and bermuda-fescue mixes.

Worker Exposure

Typical applications to Oklahoma pastures are custom ground applications, air applications, and ground applications by the producer himself. Producer applications utilize either a boom type sprayer or boom-less sprayer pulled behind a tractor or sprayers mounted in the bed of a pickup. Hand wand applicators on truck mounted sprayers or backpack sprayers can be used for spot treatment of brush in pastures. This is not as common due to time and labor issues for Oklahoma Pasture. No hand labor activities occur after pesticide application.

Among all pastures, 2, 4-D is the most popular herbicide being used on Oklahoma Range and Pastures. 15% of total Native range acres and 14% of improved pasture acres used 2, 4-D. 2, 4-D use is followed closely by Grazon P+D at 13% of Native range acres and 11% of improved pasture acres treated with Grazon P+D.

Musk thistle control is also of importance in Oklahoma for several reasons. Musk thistle reduces pasture yield, either through direct competition with the forage plants for light, nutrients, and water, or through displacement of edible forage, as cattle will not feed on the thistle (Rees 1991). As few as one thistle plant per 1.49 m² can reduce forage yield by 23% (Trumble and Kok, 1982). In Oklahoma, musk thistle can act as either an annual or a biennial; either way, the plants bolt and flower in the spring (usually starting in early May). Each plant can produce more than 10,000 seeds (Beck et al. 1990), and the seeds can remain viable in the soil for five years or more (Jackman 1999); consequently, management of this weed can be long-term effort.

In 1998, management of musk thistle became a priority with the passage of the Oklahoma Noxious Weed Law, which requires landowners to prevent seed production of musk, Scotch, and Canada thistle on their land, with a possible penalty of a $1,000 fine per incident per day. Since then, the Oklahoma Department of Agriculture, Food, and Forestry have investigated numerous complaints about musk thistle infestation; thus far, the landowners have not been fined, but have been informed of the law and directed to their local county Extension office for management information.

In addition to cultural (mowing, digging, increasing pastures health) and chemical (herbicide) controls, musk thistle can also be managed with biological control. In the 1960s, two weevils were imported from Italy and released in the United States (Boldt and Campobasso 1981). The musk thistle head weevil, Rhinocyllus conicus Froelich, emerges as an adult in early May, synchronous with musk thistle flowering. The female lays 200 eggs on the underside of the flower head bracts; the larvae hatch, and feed directly on the seeds within the flower head. As few as nine larvae per head can reduce viable seed by 98% (Roduner 2001). The larvae pupate, emerge as adults in mid-July, and spend the rest of the year underground, emerging again in the spring. The musk thistle rosette weevil, Trichosirocalus horridus (Panzer), also emerges as an adult in May, and feeds on the thistle leaves. In the fall, the females lay 2000 eggs on the leaves of the new thistle seedlings; the larvae feed on the meristematic tissue in the rosette stage of the plant, and over winter as eggs, larvae, pupae, or adults. Together, both of these weevils can eventually clear a pasture of musk thistle, though it can take as long as ten years.

Since 1991, educators in the Oklahoma Cooperative Extension Service have been collecting and re-releasing these weevils around the state (Medlin et al. 2003). These spring "Weevil Round-Ups" have resulted in the release of 583,500 weevils into 41 counties. Recommendations for integrated management of musk thistle are to (1) maintain optimal pasture health (e.g., not overgraze, etc.); (2) release musk thistle weevils into pasture areas that are difficult to spray (e.g., fence rows, creek beds/gullies, right-of-ways, etc.); (3) apply herbicides annually in the rest of the pasture for the next 3-4 years; (4) monitor weevil activity, and when populations have increased in the untreated areas, the weevils will move to any thistles in the rest of the pasture, thus decreasing or eliminating the need for continued herbicide use.

Western ragweed is one of the most common weeds on Oklahoma rangelands. It has long been considered an aggressive competitor with grasses and is generally unpalatable to cattle. Western ragweed is distributed across all of Oklahoma and most of the United States because it can adapt too many environments.

Seed production is of secondary importance for western ragweed since it is a perennial and produces new growth from rootstocks. When seedlings establish, they will not flower or produce additional shoots during the first growing season. The second year, additional shoots will develop from creeping rootstocks and form a clone.

Most often, western ragweed increases with increasing grazing pressure. This is likely the result of a number of factors, including western ragweed’s response to additional sunlight. Also, when grasses are grazed closely, their root growth stops or is severely set back. Even in lightly stocked pastures, western ragweed may become abundant where spot-grazing occurs.

Control

The use of mowing as a control method is inefficient and highly ineffective. Damage to the main stem in the first half of the growing season will result in a short bushy plant with many branches rising from the base. Continuous mowing through-out the summer is necessary to prevent flowering and must be done for several years to starve the extensive root system of a clone. In the process, the vigor of the grasses would be harmed, reducing their ability to compete.

Prescribed burning should not be considered as a method of controlling western ragweed. While prescribed burning has a number of benefits and should be considered a good practice of rangeland management, eastern ragweed’s response to fire is highly variable. Western ragweed tends to decrease following fire in short grass prairie. Most studies in tall grass and mixed prairies; however, have found that western ragweed either increases following spring burns or experiences no change at all.

Chemical control requires proper timing. For 2,4-D, this means application should occur when air temperature is warm, soil moisture is good, and the targeted plants are 2 to 4 inches tall and actively growing. Western ragweed reaches this point of development in early May. Eighty to 100 percent control of western ragweed can be achieved under these conditions with 2,4-D at a rate of 1 pound per acre. Dicamba plus 2,4-D and Picloram plus 2,4-D can provide higher levels of control, but they are not as cost-effective as properly applied 2,4-D. The greatest economic returns from applying 2,4-D will occur on the most productive sites, but care should be taken in treating only portions of a pasture. Cattle are sometimes attracted to herbicide-treated areas, regardless of the level of forb control. Such attraction could cause them to over-utilize the treated area the first summer after treatment. Chemical control is most cost-effective when it is followed by proper grazing management. Since an abundance of forbs is often the result of overgrazing, failure to adjust stocking rates will likely cause the problem to recur. Use of moderate stocking rates can extend the life of the herbicide treatment so that future control may only be necessary during wet years.

Because grazing management is usually the cause of western ragweed problems, it is also an excellent method of control. When ragweed problems exist, the first step should be to examine the current grazing practices. Usually, a lack of grass is not the result of dense stands of western ragweed, but an abundance of western ragweed is often the result of grasses being over-utilized. The best way to limit ragweed production is with grazing management that limits the avail-ability of light to western ragweed and maintains the vigor of grasses.

Eastern red cedar is a major brush problem in Oklahoma grasslands. Historically, fire prevented eastern redcedar movements into Oklahoma grasslands. The wide distribution of redcedar can be attributed partially to the early day practice of using redcedar plantings around homesteads, shelterbelts, and cemeteries. Over the years, seeds from mature trees have spread to adjacent road right-of-way and woodlands. A redcedar tree with a 6 foot crown diameter on a shallow prairie range site will reduce forage by about 6 pounds.

Most herbicides currently used for control of weeds and brush are not effective on redcedar. Redcedar can be tolerant of 2,4-D and other herbicides at rates normally used for weed and brush control. Foliar and soil applied herbicides can be used to control redcedar if desired. Broadcast foliar sprays are not very effective. The dense nature of the tree crown and waxy nature of the leaves make herbicide penetration difficult. Foliar sprays need to be applied as a spray to drip basis to achieve any success. Treatments of foliar sprays should be applied in late-May and early June when soil moisture and other growing factors are favorable. Soil applications are more effective than foliar treatments for the control of redcedar. Soil treatments should be used on new cedar trees as redcedars that are over 5 feet in diameter results in marginal tree kill. It is very important to make these applications from March through May as these are the months of adequate rainfall to move the herbicide into the root zone for uptake by the redcedar during active growth.

Mechanical control can be a very effective way of controlling redcedar since it is a single-stemmed tree that does not sprout from roots or underground stems. Mechanical methods include mowing, chaining, chopping, shredding, tree pulling, bulldozing, and sawing. One advantage to this type of control is that no reproducing male trees can be left for wildlife habitat without increasing the spread of redcedar. Mechanical control also becomes an option since prescribed fire may not be an option due to large of trees, insufficient fuel load, or redcedars dispersed to far apart to control by fire.

When conditions are favorable for using fire it is the most economical way of controlling redcedar in range and pastureland. Tree height and fuel load are the primary factors affecting kill. Trees less than 1 foot tall are killed by nearly any type of fire and burning conditions. Trees from 1 to 5 feet in height can be consistently controlled by burns with fuel loads above 4000 lbs/acre. Trees over 6 feet in height are less effectively controlled with fire under the normal range of fuel loading in Oklahoma. Taller trees often are partially crown scorched in a fire. Once redcedars have been scorched they can individually be reignited by hand after 2 to 3 weeks with a propane torch or similar device.

Sericea lespedeza is an introduced perennial legume, relatively free of insect and disease problems. It is very competitive and highly tolerant of a variety of conditions, which are among the reasons it has become an invasive and noxious weed in Oklahoma. Sericea was planted in the past to control soil erosion and provide forage for livestock and wildlife. From these plantings, it has been spread by animals and movement of hay contaminated with sericea seed to native prairies, shrub lands, forests, and introduced pastures. Normal management practices such as grazing, burning and applying 2,4-D herbicide do not control sericea lespedeza. Some have argued that it should be classified as a noxious weed in Oklahoma.

Sericea has been found growing in all parts of Oklahoma, except the Panhandle. Sericea uses water less efficiently than many other warm-season plants and does best when annual precipitation is 30 inches or more, which explains why it is a greater problem in eastern Oklahoma. However, sericea occurrence has been reported on Conservation Reserve Program (CRP) lands and rangelands in western Oklahoma.

The best control approach is early detection, isolation of infested areas and control of individual plants with herbicides like Remedy and Ally. Once established, an integrated approach to control will be necessary to minimize the damage. Conventional management practices of prescribed grazing and prescribed fire have not been effective in preventing the spread of sericea in rangelands, introduced pastures and forests. It is difficult to give grasses a competitive edge with season-long and rotational grazing because cattle will select grasses and leave the sericea plants because of low palatability. If grasses are over-utilized, the invasion of sericea will be hastened. Some suppression of sericea has been observed after mowing or burning followed by intensive early stocking (IES) with stocker cattle. Livestock will consume the seeds and deposit them elsewhere in manure, so it is advisable to temporarily fence these infested areas to exclude livestock until the sericea has been controlled. This is particularly important during late summer and fall when the plants are flowering and producing seed. Goats may provide control, since they have been known to eat sericea.

Spring burning removes the old dead growth of sericea, but has no negative effect on established plants. In fact, fire probably increases seed germination by scarifying the seed and thus promotes the establishment of new plants. Seeds of sericea germinate in early April through June. Seedlings establish when moisture conditions are favorable; thus, burning most likely will result in a denser stand of sericea if control measures are not implemented. However, the increased seed germination following fire should improve the effectiveness of a control program that involves spraying in July with Remedy or spraying in September with Ally.

Mowing will reduce the vigor of sericea plants if they are cut closely multiple times each year. Plants should be mowed each time they reach a height of 12-18 inches. The most damaging time to cut sericea is late in the growing season when the plants are trying to build root reserves for the next year’s growth. However, mowing will not kill sericea and may damage desirable grasses, depending on the timing and frequency of cutting. In addition, a large sericea seed bank will remain in the soil, ready to germinate when conditions are suitable.

None of the commonly used herbicides for broad-leaved weed control have provided good control of sericea lespedeza. Amber, 2,4-D, Grazon P+D, and Weedmaster have been ineffective on established stands of sericea. In studies conducted at three locations in 1988 and 1989, sericea was not controlled by 2,4-D at rates up to 2 lb/acre and minimal kill was achieved with 1 quart/acre of Grazon P+D or Weedmaster. Sericea was, however, adequately controlled with 1 pt/ac of Remedy (better than 93 percent in five of the studies and 79 percent in the sixth study). In additional studies in 1995, excellent control of sericea was obtained with 1 pt/ac of Remedy applied in June and July and Ally applied in September. Currently, the maximum labeled rate for Ally is 0.3 oz/acre. Broad-leaved plants like western ragweed also are controlled with a June application of Remedy. It is critical the sericea plants be actively growing at the time of herbicide application or the treatment will not be effective.

Since areas infested with sericea often have an enormous supply of seed in the soil, follow-up treatments will be required. Seedlings emerge after the mature plants are killed and by the third or fourth year, sericea will dominate the area again.

Preliminary results indicate mowing before application of Ally or Remedy can increase the level of control. Combining a single mowing in June or July with an herbicide treatment in July or September provided 100 percent control of sericea seedlings. Using fire to encourage seed germination before spraying may be helpful in diminishing the seed supply in the soil, reducing the amount of follow-up treatment needed.

A combination of grazing management, fire, mowing and herbicide offers the most effective control of sericea lespedeza.

An example of how these techniques may be used together is as follows:

1. Use light or moderate stocking, allowing fuel to accumulate for a prescribed burn.
2. Burn in spring to encourage germination of sericea seed and remove old growth.
3. After fire, intensively early stock (IES) areas until mid-June.
4. Apply Remedy at 1 pt/acre in mid-July.
5. Apply Ally in September to areas missed by Remedy.
6. During September and October, exclude livestock from areas with sericea stands.
7. Thereafter, spot treat sericea with Remedy or Ally as needed

Contacts

Darren Redfearn
Assistant Professor
Extension Forages
Plant & Soil Sciences
405-744-9648
rdaren@okstate.edu

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