HOW TO CONTROL NOXIOUS PLANTS

Joseph F. Pechanec, Charles E. Fisher, Kenneth W. Parker

NOXIOUS range plants rob the livestock industry in many ways. In Texas alone, the annual loss from mesquite and juniper has been estimated to be 20 million dollars.

Some, like big sagebrush, mesquite, or oak, are shrubby or treelike, produce little forage, and obstruct grazing use. Other noxious plants, such as cheat-grass and snakeweed, produce poor forage and lower grazing capacity.

Poisonous plants such as larkspur, orange sneezeweed, and bitterweed sometimes cause such serious losses among cattle and sheep that some kinds of livestock must be taken off the range.

Still other noxious plants, like dry cheatgrass where it is predominant on a range, have been estimated to increase the fire hazard 500 times.

Against all noxious plants the charge can be made that they occupy sites often to the almost complete exclusion of desirable species, use up limited moisture supplies, and produce little forage in return. Moreover, heavy stands often obstruct range reseeding or natural revegetation. Usually it is necessary to control or thin such growth before desirable forage species can be reestablished in abundance and, in many instances, accelerated erosion arrested.

The practicability and benefits of using proved methods of control have been demonstrated on a wide scale with sand sagebrush, mesquite, big sagebrush, and other noxious plants. Costs of mowing sand sagebrush in Oklahoma two successive years in June were mostly repaid in extra beef production and additional grazing capacity of the land during the first two winters.

Soil-binding qualities of the vegetation and water-holding capacity of the land also were improved, livestock movements over the entire area were facilitated, and screwworm infection was reduced. When the brush that protected them was removed, populations of kangaroo rats and other destructive rodents were reduced by coyotes and hawks.

The removal of mesquite has brought similar improvements. Trials in Arizona demonstrated that even though the potential production of range lands was low, the initial prewar cost of $1.89 an acre for killing mesquite with sodium arsenite could be repaid by increased cattle gains within 10 years. Control of the mesquite more than doubled usable forage production, improved the condition of the soil surface, reduced erosion, facilitated the handling of cattle, and probably reduced screwworm, infection.

The control and removal of big sagebrush likewise has paid dividends. Burning to remove sagebrush (at a cost of 19 cents an acre) in southern Idaho, where reseeding to perennial grasses was unnecessary afterward, doubled the grazing capacity and greatly simplified the handling of range sheep and cattle. Plowing to eradicate the sagebrush in southern Idaho and Utah (at a cost of $1.30 to $5 an acre), followed by reseeding, increased grazing capacity 9 to 12 times, increased soil protection, and made easier the movement of range sheep and cattle. On the basis of the increased grazing capacity alone, the initial cost of brush control and seeding was repaid in 7 to 10 years.

Some points to be considered in planning an effective program to control noxious plants are:

Undertake large-scale control only where practical, effective, and economical procedures can be used. Such methods are available for many sites and situations.

Control noxious plants when they first invade a range. It will cost much less then and may prevent further encroachment and deterioration of the range.

On heavily infested ranges, begin control work on parts where benefits can be most effectively utilized in the herd or range management plan. Start also on areas of greatest promise for forage production those with fertile soils and with favorable precipitation or with possibilities for water spreading.

With widely distributed stands of poisonous plants first eliminate the toxic plants from areas near permanent water, along trails and stock driveways, or wherever livestock tend to congregate. This will eliminate likelihood of livestock losses.

Avoid areas where the elimination of dense stands of noxious plants seriously increases the risk of accelerated erosion. For example, it is well to leave sand sagebrush on sand dunes, big sagebrush in places where the soils arc sandy or the slopes are steep, and juniper on rocky, shallow soils.

Choose a method suited to the site and type of stand. Hand methods of control are practical for sparse stands of juniper, but power machinery is the only practical attack on stands thicker than 150 trees to an acre.

Pick the most effective season. Mowing sand sagebrush in Oklahoma is most effective if done in June, for example. Burning sagebrush in southern Idaho is best done in the late summer and early fall. The use of 2,4 D is most effective during active plant growth.

In places where noxious plants make up most of the plant cover, reseed to desirable forage species after the noxious plants are killed. This will prevent serious loss of soil, insure a rapid increase in forage production, and retard the establishment of seedlings of noxious plants.

The choice of the method of attack is governed by its effectiveness, cost, adaptability to existing conditions, expected benefits, and possible hazards.

Hand pulling and grubbing the plants are efficient but costly methods for some species. Hand pulling water-hemlock along stream banks is a good way. For species such as larkspur, western sneezeweed, or the mesquite seedlings that have the taproot type of root system, grubbing thoroughly and for several years in succession gives good results. But on species like poison milkweed or St. Johnswort, which reproduce from underground rootstocks, grubbing and pulling are apt to give disappointing results. Because of its high cost, grubbing is practical only to clean out seedlings and sparse stands of noxious plants or to eradicate toxic plants from areas where cattle and sheep congregate.

Mechanical grubbing has been used effectively to remove dense stands of mesquite and big sagebrush, but it is relatively expensive because it takes a considerable outlay for equipment.

Mowing, an inexpensive method, is especially suited for controlling sand sagebrush. It is also good on such shrubs as burroweed and jimmyweed, which do not sprout readily from the stem base or roots. Often mowing may be used in rock-free areas to prevent seed formation by annual weeds or grasses like cocklebur and cheatgrass. But with most herbaceous perennials that die back to the ground each year ( such as larkspur, St. Johnswort, or sneezeweed) or shrubby perennials that sprout readily from the roots ( such as rubber rabbitbrush, chokecherry, or mesquite), mowing is rather ineffective unless it is carried on in conjunction with chemical control.

Railing is inexpensive and has been used widely to eradicate big sagebrush. It consists of uprooting, breaking off, or mashing down the old big sagebrush plants by dragging a heavy implement made from railroad rail over the area. Railing is adapted to nonsprouting shrubby species that are stiff and brittle. It has no value for herbaceous species or shrubby species that sprout from the roots or that have flexible tops.