Bill Johnson, Andy Kendig, Reid Smeda and Fred FishelDepartment of Agronomy

Johnsongrass (Sorghum halepense) is a difficult perennial grass weed the reduces yields in corn, serial sorghum, soybean, cotton and also leguminous forages. Initially introduced right into the United states as a forage crop, the is now an agricultural pest in most states south of the 42nd parallel. Dense johnsongrass infestations severely minimal corn manufacturing until the fairly recent introduction of Accent and Beacon herbicides. Number of states have legislation request eradication or regulate programs. Johnsongrass is noted as a noxious weed by the room of Agriculture, which requires that landowners take actions toward controlling and also eradicating the weed ~ above all building owned or under their control.

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Growers now have numerous tools to regulate this weed. As with most other weeds, the key is come implement multiple manage strategies when johnsongrass is first observed and also not wait until it is steady established.

Figure 1Mature johnsongrass was standing 6 to 8 feet tall.

Figure 2Johnsongrass seed head.

Figure 3Johnsongrass has a large, jagged-edged, membranous ligule.

Figure 4Rhizomes the johnsongrass space covered with orange scales.

Plant characteristics

Johnsongrass is well adapted to complete with chop plants and also to spread out to new areas. An upright perennial, it often grows 6 come 8 feet tall (Figure 1). The has broad leaves with thickened whitish midribs; that is panicles (seed heads) are open (Figure 2), and also the plenty of branches assistance thousands the spikelets from which seeds are easily shattered. A key identifying characteristic of the vegetative phase is its fairly large, jagged-edged, membranous ligule (Figure 3). Shattercane can conveniently be puzzled with johnsongrass. The most obvious difference is that because shattercane is an yearly grass, that does not develop rhizomes. The sheet blade the shattercane, as much as 3 inches wide, is commonly much wider than the 0.8-inch-wide leaf blade of johnsongrass. In enhancement to a usual fibrous root system, johnsongrass produces special cream-colored rhizomes, extended with orange scale (Figure 4).

During 1992 assorted biotypes of johnsongrass in Mississippi to be reported to exhibition resistance come Fusilade DX used at labeled rates. Resistance appeared in areas that had been treated v Fusilade and also Poast plus in at least eight that the vault 10 years. Due to the fact that that time, at least 5 counties in Mississippi have actually johnsongrass populations evidenced resistant come Fusilade, and there are current reports the resistant johnsongrass in Kentucky. Commonly, resistant populations of johnsongrass are not sensitive to Fusilade DX or guarantee II, no matter what price is applied. Elevated yongin to Poast/Poast plus has additionally been noted, however rates three- to fivefold higher than recommended usually are effective. Field use rates of Select, another selective grass herbicide, are efficient in regulating resistant johnsongrass.


Its capability to develop seed and also rhizomes and spread come uninfested locations contributes to making johnsongrass a menacing weed. Rhizomes are extensive and also are developed in the optimal 10 customs of soil but have been found at depth of 5 feet. Johnsongrass easily reproduces from rhizomes and also seed; seedling plants can initiate rhizomes as few as 19 days adhering to emergence.

A single plant might produce much more than 80,000 seed in a solitary growing season, and 275 feet that rhizomes. Seed shatter easily and fall come the ground beneath plants that produce them. Instead of germinating uniformly, seeds have the right to remain dormant and also produce tree over number of years. Johnsongrass seed have the right to remain viable in the soil for an ext than 10 years.

Johnsongrass typically grows in productive bottomlands follow me creek and river banks and in upland fields. Irrigation ditch financial institutions are also overgrown through johnsongrass, and seed is lugged by the water. In a new location, johnsongrass diffusion rapidly and soon i do not care a serious problem. Tillage equipment can spread out the rhizomes, and birds spread out the seed.

Agricultural seed, hay and various breed cub feeds sometimes end up being contaminated through johnsongrass seed. In the past, watermelons transport from the south were often bedded in johnsongrass hay, i m sorry was brushed up out at assorted dropoff points and contributed come its spread.

Interfertility with various other sorghum species

Plant breeders, seed dealers and also growers regularly observe off-type tree or "rogues" the hybrid grain sorghum. Typical rogues are the high outcrosses to sudangrass, johnsongrass or various other sorghum types. Sorghum outcrosses v johnsongrass together the male parent regularly have rhizomes resembling those of johnsongrass. Johnsongrass-grain sorghum hybrids can become a far-ranging weed threat.

Cultural control

Preventing johnsongrass from becoming established in new areas is the best accessible control method, because the weed diffusion in so numerous ways. Because johnsongrass is a perennial weed, single cultural control actions or herbicide applications rarely provide adequate control.

Johnsongrass control programs should

Prevent spread of rhizomes native infested come uninfested areas.Kill or weaken developed plants and also their secret rhizome system.Control seedlings originating from shattered seed.Prevent manufacturing of seed and also its spread out to new areas.Use autumn tillage to bring rhizomes to soil surface, wherein they may be eliminated by winter conditions.

These objectives are very closely related and are equally important to the success or fail of a regulate program. In minimal infestations, that is feasible and preferable to use herbicides to kill the weed and also prevent seeds production. The vital time to death johnsongrass is when the weed is coming to be established and before it has actually spread end the whole field. Because that sites with developed infestations, a autumn application that Roundup or Touchdown will certainly kill emerged tissue and also often developing rhizomes.

Growing early-maturing crops, plowing immediately after harvest, and also tilling as necessary are typical methods to break up rhizomes and weaken johnsongrass stand in cultivated areas. Johnsongrass responds come tillage prefer most hard perennial weeds. Intensive tillage will suppress rhizome johnsongrass. Middle tillage will break and spread rhizomes and allow johnsongrass to thrive. Johnsongrass will certainly spread relatively slowly in true no-till regimes; however, given sufficient time, infestations might still come to be severe. Serious infestations often an outcome in pastures converted to heat crops. Untreated johnsongrass in fence rows and ditch financial institutions is a common source of johnsongrass seed and also vegetative encroachment into fields. Clues sprays on fences and also ditch banks can eliminate these sources of seeds and rhizomes.

Alfalfa competes well v johnsongrass for a restricted time however will eventually weaken. Repetitive mowing of one alfalfa-johnsongrass mixture will prevent johnsongrass from producing seed and also will inhibit rhizome development. Extensive grazing and also mowing have the right to be provided to reduce a stand of johnsongrass. If grazed or mowed closely for at the very least two years, the plants come to be weak and stunted and the rhizomes come to be concentrated near the soil surface. Plowing in late autumn exposes the rhizomes to low winter temperatures and also reduces the was standing considerably. Because that infested areas that can not be tilled or sprayed, extensive grazing or mowing is most likely the finest control.

Johnsongrass control with herbicides

To minimize johnsongrass infestations with herbicides, it will be vital to use an integrated technique consisting that soil-applied herbicides, postemergence herbicides, crop rotation and tillage. Weedy tree such together johnsongrass adapt quickly to a cultural system the does not change from year come year. An instance of this type of device is consistent soybean production such as occurs in plenty of river and also creek bottoms. Chop rotation is important to disrupt the physical environment that johnsongrass and many other weeds live in and also will aid to minimize seed and rhizome production. Herbicide rotation is important to minimize choice pressure for herbicide-resistant biotypes.

The program mentioned listed below are draft to regulate other weeds in enhancement to johnsongrass. However, this programs room designed for areas where johnsongrass is not adequately regulated by present methods. For manage methods to be effective, growers must be diligent and also apply control techniques as regularly as necessary.

CornIn no-till corn production, any type of herbicide that has actually postemergence grass activity will carry out some control of seedling johnsongrass. In conventional-till corn production, Eradicane or an additional product containing EPTC (Eradicane) deserve to be used as a preplant incorporated treatment. Rhizomes need to be cut up into little pieces using numerous diskings prior to treatment. Incorporate Eradicane immediately after application to minimize volatility losses. However, the burndown or preplant integrated applications will not provide adequate season-long control and extr control steps will be needed.

Postemergence herbicides because that johnsongrass control in corn incorporate Accent, Beacon, Poast HC and Roundup Ultra. The initial applications of accent or Beacon have to be used to 4- to 10-inch-tall seedling johnsongrass and 8- to 14-inch-tall rhizome johnsongrass. If regrowth occurs, a second application have the right to be made as soon as johnsongrass regrowth is 8 come 14 inches tall. Accent have the right to be used as a broadcast therapy on corn till it is 24 inch tall. Interval applications can be made come 24- come 36-inch corn by using drop nozzles. Beacon have the right to be applied as a broadcast spray to corn that is between 4 and 20 customs tall. Do not use Accent or Beacon come corn that has been treated with respond to insecticide. Consult the brand for restrictions with other organophosphate insecticides and also postemergence herbicides.

In SR (sethoxydim-resistant or Poast-tolerant) corn, Poast plus or Poast HC should be applied initially to 10- to 25-inch johnsongrass. If regrowth occurs, a sequential treatment deserve to be used to 12-inch johnsongrass regrowth. There room no insecticide restrictions and also Poast HC can be applied until corn begins to burned pollen.

When Roundup-Ready corn has received full federal approval, Roundup Ultra deserve to be used to johnsongrass as much as 24 customs tall. If regrowth occurs, a sequential treatment have the right to be used to 12-inch johnsongrass regrowth. Consult the brand for phase of growth and insecticide restrictions.

Soybean and also cottonIn no-till soybean or cotton production, together in corn production, any kind of herbicide that has actually postemergence grass task will provide some regulate of seedling johnsongrass. In conventional-till soybean or cotton production, Treflan and Prowl have the right to be used preplant incorporated and also will administer some regulate of seedling johnsongrass. Once incorporating these herbicides, set the perform to run 4 customs deep and also make two passes over the cure area come ensure sufficient mixing that the herbicide v the soil. However, together in corn production, the burndown or preplant included applications will certainly not provide adequate season-long control, and added control actions will be needed.

Postemergence herbicides for johnsongrass regulate in soybean and cotton include Assure II, Bugle, Fusilade DX, Fusion, Poast Plus/Rezult G/Conclude G, and Select in regular, non-herbicide-tolerant soybean or cotton. Every one of these herbicides carry out acceptable control, although assure II, Fusilade and Select space the preferred herbicides for johnsongrass. Roundup Ultra have the right to be used in Roundup-Ready soybean and cotton. In thick infestations, single applications of any of these herbicides will provide incomplete control. Much better control is obtained with split applications. It is recommended the the lower herbicide prices be offered on seedling johnsongrass the is less than 10 inches tall. The higher rates room recommended for usage on rhizome johnsongrass taller than 10 inches. The recommended approach is come target johnsongrass that is 10 come 18 inch tall. Smaller johnsongrass has tiny leaf area and also consequently absorbs restricted amounts of herbicide for finish rhizome control. Regrowth after ~ the very first postemergence application indicates that there is a significant amount that rhizome johnsongrass present in the field, and also a 2nd postemergence application will be needed. To control regrowth, apply the greater rate the a postemergence herbicide come regrowth that is 6 to 12 inches tall. Because that regrowth applications, the is a good idea to use a various herbicide than that supplied for the initial application to avoid an option of herbicide-resistant johnsongrass biotypes.

Adjuvants and cultivation in corn, soybean and cottonConsult the manufacturer's label for the proper adjuvant because that postemergence herbicides. Permit seven days after postemergence herbicide applications before any cultivation is practiced. Growing too shortly after herbicide applications will mitigate johnsongrass control as stems and also rhizomes room broken before the herbicide deserve to be translocated. Growing seven to 10 days after herbicide applications, ~ the herbicide has actually translocated, will further weaken the herbicide-injured rhizomes and increase johnsongrass control.

Alfalfa, birdsfoot trefoil, cloversA preplant included treatment the Balan can be used for control of seedling johnsongrass and also other yearly grasses in alfalfa. Rhizome johnsongrass will certainly not it is in adequately controlled with Balan alone. Balan must be included within four hours ~ application. Change weed regulate may result if organization is delayed an ext than eight hours.

Postemergence herbicides incorporate Poast/Poast Plus and also Select. This herbicides can be provided on new or established seedings and also can additionally be used when alfalfa is one of two people dormant or nondormant. Apply Poast, Poast plus or select to 10- to 25-inch-tall johnsongrass. If regrowth occurs, sequential applications have the right to be do with similar rates to 12-inch johnsongrass regrowth. Top the label for the appropriate adjuvant for the postemergence herbicides.

Grain sorghumBecause johnsongrass is very closely related to other plants in the sorghum family, including grain sorghum (Sorghum bicolor), existing herbicides that manage johnsongrass additionally control or death grain sorghum. The best management exercise for johnsongrass control in grain sorghum will be to flourish an alternate crop that has more available registered herbicides.

Selective herbicide applications for johnsongrass control

Selective application devices can administer economical johnsongrass manage in any kind of of the above-listed crops. Usual johnsongrass infestations are spread unevenly throughout the field. Chemical expenses can be decreased by utilizing a ropewick applicator or by clues spraying the infested areas. In a ropewick applicator, mix 1 component Roundup or Touchdown through 2 components water. Operation the ropewick applicator in two directions across the field so the johnsongrass is wiped or angry on both sides. The ropewick must be for sure run over the crop canopy come avoid contact with crop foliage. Part dripping and crop injury is inevitable; therefore, that is best to use a commercially available ropewick bar designed to minimize dripping.

Spot spraying can also be an economical johnsongrass monitoring tool. In soybean and also cotton, the selective grass herbicides mentioned earlier may be combined with water in a 1 to 2 percent solution and spot sprayed through hand wand, ATV-mounted sprayers, or tractor-mounted sprayers. Roundup or Touchdown clues sprays can additionally be used but will cause injury or fatality to plants that room not tolerant that glyphosate herbicides (Roundup or Touchdown).

Preharvest johnsongrass control

Johnsongrass control before harvest will aid to reduce rhizome and also seed manufacturing for succeeding rotational crops. Roundup is labeling for application to maturation corn, cotton, grain sorghum, soybean, and wheat. Double-crop soybean may specifically benefit if johnsongrass is injected in the coming before wheat crop. Roundup may be used to stand soybean that has lost every green shade in the ford as long as the crop is no being grown because that seed. Roundup may be applied to corn in ~ 35 percent grain moisture or less, to cotton when 60 percent that the bolls room open, to serial sorghum in ~ 30 percent moisture or less, and also to wheat after the hard-dough stage.

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Soybean and also wheat need to not be harvest for 7 to 10 work after applications to enable herbicide translocation. This applications might be of restricted utility in soybean and cotton, as the applications time is frequently close to frost. Unless herbicide applications space made at least seven to 10 days prior to frost, insufficient translocation will occur and the applications will certainly not be effective.