Weed Control in Grain Sorghum

DIVISION OF AGRICULTURE RESEARCH & EXTENSION University of Arkansas System

Chapter 8 Arkansas Grain Sorghum Production Handbook

Tom Barber, Bob Scott and Jason Norsworthy

Weed competition in grain sorghum reduces Most grain sorghum is planted in early to yields, causes harvesting losses and increases mid-April throughout the state to allow flowering seed content of the soil seedbank. Even light prior to a large buildup of sorghum midge. weed infestations in the early growing season Although this early planting reduces insect will reduce yields significantly. Grain sorghum pressure, it contributes additional stress to the seedlings grow slowly and are weak competitors grain sorghum seedling. Grain sorghum was to most weeds. Research data have shown introduced from the warmer climates of Africa and grows best when soil and air temperatures rise above 70°F. Seedlings stressed from cool and wet soils are much more sensitive to weed competition and herbicide injury.

The most troublesome weeds in Arkansas grain sorghum include johnsongrass, broadleaf signalgrass, barnyardgrass, crabgrass, morningglory, pigweed, prickly sida and sicklepod. There are fewer control options for weed control in grain sorghum than in corn, cotton and soybeans. Grain sorghum lacks tolerance to many of the commonly used grass and broadleaf herbicides Figure 8-1. Weeds compete for light, moisture and and is occasionally injured even by herbicides nutrients. labeled for use in sorghum. Unfavorable weather conditions such as cool, wet soils, delayed crop that one pigweed plant per 3 feet of row left emergence, deep planting, seedling diseases, uncontrolled until sorghum reaches the 3-leaf poor soil physical conditions and poor quality stage will reduce yields by 10%. Heavy infestations seed may contribute to seedling stress and of grassy weeds may cause up to a 20% yield herbicide injury. reduction in the first 2 weeks after sorghum germination. Late-season weed infestations have Grain sorghum is almost always included less effect on produced yields but reduce harvest- in a crop rotation schedule. Herbicides such as ing efficiency and may reduce harvested yields. Pursuit, Reflex, Flexstar and other generic

UPDATED 4-2015 1 fomesafen applied to soybeans the previous year Herbicide programs for effective weed control can remain in the soil and cause stand reductions must be developed based on weed spectrum and and/or injury to sorghum. ResolveQ, RealmQ soil type. Your county Extension agent receives and AccentQ in corn and Staple applied to cotton extensive training on weed identification and the previous year can also injure sorghum. In weed control technology and is available to assist addition, Newpath or Clearpath used in rice will in developing economical and effective control carry over to grain sorghum. Often the carryover programs. MP44, Recommended Chemicals for Weed herbicide injury is not visible in very young and Brush Control, is updated annually to reflect sorghum but becomes apparent at the 3- to 6-leaf the most current information on herbicide label stage of growth. For carryover information on changes and revised recommendations based on common herbicides, refer to the Extension publi- research data. cation MP519, Row Crop Plant-Back Intervals for Common Herbicides (available at www.uaex.edu). Herbicides Used for Weed Control A combination of tillage and chemical weed control is usually most effective in grain sorghum. Effective weed control programs start with Effective chemical weed control is dependent clean fields at planting. It is critical to remove upon proper weed identification and matching existing cool-season weeds with tillage or herbicide rate and timing to the particular weeds. herbicides prior to planting. Glyphosate and Cool-season weeds should be destroyed prior to glyphosate in combination with 2,4-D are very planting to ensure that crop seedlings emerge effective preplant herbicides. competition free. Most winter weeds may be controlled with glyphosate, 2,4-D, dicamba Atrazine is the basis of most chemical weed or paraquat. (For additional information, refer to control programs in Arkansas grain sorghum. It Extension publication MP44, Recommended Chemi- is estimated that greater than 90% of the acres cals for Weed and Brush Control, available from planted receive at least one application of county Extension offices throughout the state and atrazine. In sites where weedy grasses are not a at www.uaex.edu.) problem, atrazine may be the only herbicide applied. Although atrazine has some activity on Broadleaf weeds may be controlled grassy weeds, it is considered a broadleaf herbi- postemergence, but there are few options for cide. It may be combined with the chloroac- postemergence grass control. Grassy weeds are etamide herbicides such as Dual II Magnum, most effectively controlled with preemergence Outlook and Lasso to broaden the weed control herbicide applications. Johnsongrass (Sorghum spectrum. Concep®-treated seed must be planted halepensea) and grain sorghum (Sorghum vulgare) if any of the chloroacetamides are to be used. are genetically very similar, and there are no These active ingredients are also sold in premixes approved herbicides that will selectively remove with atrazine under different names. Bicep II johnsongrass from grain sorghum. Even light Magnum and Guardsman Max are examples of infestations of johnsongrass in other crops atrazine plus chloroacetamide premixes that planted the previous year often turn into heavy require Concep-treated seed. infestations in grain sorghum due to lack of Preemergence herbicides are applied after selective control. Fields with a history of johnson - the sorghum has been planted and prior to grass or bermudagrass should not be planted to emergence. The chloroacetamides such as Dual grain sorghum.

2 UPDATED 4-2015 Magnum are taken into the weedy plants through the emerging coleoptiles and have little or no activity on emerged weeds. These herbicides must be applied before targeted weeds germinate. Atrazine is effective as a preemergence or early postemergence herbicide. Dual Magnum, Lasso and Outlook primarily control grasses such as crabgrass, barnyardgrass and broadleaf signalgrass but also suppress yellow nutsedge and offer some control of pigweeds. Combinations of these prod- ucts with atrazine as tank mixes or premixes applied preemergence will control most seedling grasses and broadleaf weeds for 3 weeks. Figure 8-2. Injury from high rates of Dual and atrazine can occur under cool/wet conditions. Rainfall or irrigation is required to incorporate the herbicides with the soil for activity. This is often referred to as “activation” of the herbicide. However, large rains immediately after application Postemergence may move some of the herbicide into contact Weed Control with the germinating sorghum seedling and may actually be taken into the germinating seed as it Control of weeds once they emerge in grain imbibes water. This usually results in delayed sorghum can be difficult, especially with grass emergence and some crop injury. Under good species. There is currently no available option growing conditions, the symptoms are usually for control of johnsongrass once it emerges in only cosmetic and the sorghum resumes normal grain sorghum fields. Other grasses such as growth 7 to 10 days after emergence. broadleaf signalgrass, crabgrass and barnyardgrass can be controlled while they are small with Applying high rates (2 pounds active ingredi- atrazine (AAtrex) and quinclorac (Facet L) applied ent) of atrazine preemergence to sorghum is postemergence. Atrazine applied at rates higher considered to be high risk. Significant stand losses than 1 pound active ingredient per acre postemer- and delayed development of seedlings are com- gence may injure and/or kill sorghum in cool mon following high rates of atrazine in cool, wet conditions, especially on sandy soils or if it is not weather. Splitting the atrazine applications and actively growing. Other herbicides such as 2,4-D, applying no more than 1 pound active ingredient dicamba (Clarity), prosulfuron (Peak), bromoxynil at planting followed by an additional pound early (Buctril) and Huskie are also effective postemer- postemergence has proven to be much safer to the sorghum. Atrazine may also cause more injury gence broadleaf herbicides for use in sorghum. on sandy soils. To reduce injury, wait until Paraquat (Gramoxone Max) is labeled for post- sorghum is up and growing well prior to atrazine directed use in larger grain sorghum to control application. In fields where grassy weeds are escaped weeds. Considerable crop leaf burn is expected to be a problem, a chloroacetamide expected, and this option should be used only in preemergence alone or in combination with a salvage situations where grassy weeds were not low rate of atrazine followed by additional controlled earlier in the season. (See label for atrazine early postemergence is a safe and very special precautions and injury warnings.) effective early-season weed control program.

UPDATED 4-2015 3 Standard Herbicide Program through just prior to grain head emergence. Application rates should not exceed 1 ounce per General weed control strategy for grain acre when nutsedge is 4 to 12 inches tall. How- sorghum is as follows: ever, if nutsedge is allowed to reach 4 to 12 inches tall, severe crop competition has already occurred. 1. Plant Concep®-treated seed. Only one application of Permit can be made in season to grain sorghum. 2. Dual Magnum 1-1.3 pt/A PRE, or Verdict 10 oz/A PRE, or Dual Magnum 1 pt/A + AAtrex Harvest Aids 1.5-2 pt/A PRE. The absence of approved herbicides for late-season weed control in grain sorghum often 3. V4 – Atrazine 2 pt/A + 1.3 pt/A Dual Magnum permits escaped weeds to hinder harvesting opera- POST for grass and broadleaf weeds tions. Roundup, Aim and sodium chlorate are – Or include Facet L if high grass population. effective harvest aids that will desiccate weeds and – Can include Clarity or Huskie if high popu- improve harvesting efficiency. Roundup provides lations of pigweeds and morningglories. the best harvest aid to increase efficiency; Aim should be added to desiccate vines. These should 4. Huskie can be applied for broadleaf weed be applied 7 to 10 days prior to harvest. control up to 30-inch grain sorghum.

Watch Out for Drift

Grain sorghum is sensitive to herbicide drift from other crops. Glyphosate, Clincher, Ricestar, Select and propanil are especially damaging to grain sorghum in low rates. Symptoms may range from stand losses to non-uniform growth and delayed maturity. Grain sorghum affected by

Figure 8-3. Bicep II Magnum 1.3 qt/A PRE followed by 1 qt/A AAtrex on 3-4 leaf sorghum.

Nutsedge Control in Sorghum

Yellow nutsedge and other annual sedges are becoming an increasing problem in grain sorghum. Permit herbicide can be applied for nutsedge control from 2-leaf grain sorghum Figure 8-4. Glyphosate drift on grain sorghum.

4 UPDATED 4-2015 planted in fields containing potentially high populations of johnsongrass if at all possible. Much of the Palmer amaranth in Arkansas is resistant to the ALS mode of action herbicides such as Peak as well as glyphosate. As more corn and grain sorghum are grown in Arkansas with more dependence on atrazine, triazine resistance is more likely. If you suspect resistance after a herbicide application, treat with an alternate herbicide and contact your county Extension agent. The University of Arkansas will collect samples and test for resistance. Do not let the Figure 8-5. Grain sorghum injury from Laudis herbicide POST. Grain sorghum fields next to corn weeds go to seed in the field. should be monitored carefully for drift from corn herbicides.

low rates of grass herbicides often suffers much more damage from sorghum midge due to the non-uniform growth and flowering throughout the field.

Herbicide Resistance

Herbicide-resistant weeds are becoming more of a problem in all crops. Pigweeds (Palmer amaranth) with resistance to atrazine are common in other states but have not been found in Arkansas at this time. There are some johnsongrass populations in Arkansas with resistance to ALS herbicides and glyphosate. Grain sorghum should not be

UPDATED 4-2015 5 Yellow Nutsedge Yellow - 0 9 7 7 6 7 7 0 9 0 0 0 5 5 7 0 0 3 10

SEDGES Velvetleaf

8 4 7 7 6 6 8 6 7 8 8 6 7 7 8 7 7 7 10 Smartweed

- 9 5 4 4 8 6 9 8 6 7 5 9 0 9 9 9 9 9 5 Sicklepod

- 8 5 0 8 8 8 8 9 8 4 5 8 8 8 8 0 3 6 9 Purslane

------9 6 9 9 9 9 9 7 8 9 9 9 7 8 Prickly Sida Prickly

- - - 9 7 6 9 9 9 9 8 7 8 8 8 8 7 8 3

9.5 Pigweed sp. Pigweed

9 9 9 9 4 0 0 8 9 4 9 9 0 5 8 9 9 9 8 10 Morningglory

8 8 2 8 8 8 8 9 8 5 6 9 9 8 9 8 4 7 8 4 Lambsquarters 9 7 6 9 9 9 9 9 8 5 6 8 9 6 8 8 5 8 8 9

BROADLEAVES Horsenettle

- - - - - 5 3 3 3 3 3 3 4 6 4 4 0 4 5 7 Honeyvine Milkweed Honeyvine

------6 6 6 5 6 7 9 9 6 6 5 7 7 Common Ragweed Common

- 9 7 9 9 9 9 9 8 5 5 9 9 6 8 8 8 7 8 8 Cocklebur

- - - - 9 8 9 9 9 9 9 4 9 0 8 8 8 8 9 3 Bigroot Morningglory Bigroot

- - - - 4 5 2 4 4 3 4 4 3 8 4 4 4 3 7 7 Shattercane

- 0 7 7 7 7 7 5 0 0 0 0 0 0 0 0 0 0 0 0 Seedling Johnsongrass Seedling - 2 6 4 6 3 6 3 0 3 3 0 0 0 4 3 0 0 0 8

Rating scale – 0 = No Control 10 = 100% Control. Ryegrass

- - - - - 9 9 8 8 8 9 0 0 0 6 5 0 0 0 7 Rhizome Johnsongrass Rhizome

0 0 0 0 0 0 0 0 0 3 3 0 0 0 0 0 0 0 0 0 Table 8-1. Table Rice Red

8 7 7 9 8 9 8 8 0 0 0 0 0 0 9 9 0 0 0 9 Goosegrass

6 8 9 9 9 9 9 7 0 3 3 0 0 6 7 6 0 0 0 9 Foxtail

GRASSES 6 8 9 9 9 9 9 8 0 0 0 0 0 7 8 7 0 0 0 8 Fall Panicum Fall

3 7 9 9 9 8 9 8 0 3 3 0 0 6 6 5 0 0 0 8 Crabgrass

7 8 9 9 9 9 9 0 3 3 0 0 7 8 6 0 0 0 9

9.5 Broadleaf Signalgrass Broadleaf 4 7 8 8 7 7 8 0 3 3 0 0 9 9 6 0 0 0 9 9.5

Weed Response Weed Ratings for Grain Sorghum Herbicides Barnyardgrass

6 8 8 8 9 8 9 0 0 0 0 0 8 8 6 0 0 0 9

9.5 MODE OF ACTION OF MODE 5 2 2 2 4 4 4 5 6 6 15 22 4, 5 15, 5 15, 5 15, 5 15, 5 6, 27 14, 15 15, 5, 27 Preemergence Postemergence HERBICIDES Atrazine Verdict Dual Magnum/Outlook Dual II Magnum Atrazine + Degree Atrazine + Atrazine + Micro-Tech Outlook Atrazine + Lexar Peak Permit Permit Plus 2,4-D Banvel or Clarity Facet L Facet Atrazine L+ Atrazine + oil Basagran Buctril Huskie Paraquat directed or Hood *Rating will be 0 ALS on inhibitor-resistant weeds (Group 2). **Repeat application may be needed to achieve these ratings.

6 UPDATED 4-2015 Good and Precautions Method Application of If broadleaf weeds emerge, use 2,4-D May be tank mixed with atrazine control as recommended below. or atrazine postemergence. lowed with atrazine or 2,4-D for broadleaf according to label directions or may be fol- only. only. and primrose. only. Apply in low volume – 5 to 10 gpa. Improved control of horseweed, curly dock Use with Concep-treated sorghum seed Use with Concep-treated seed only. Use with Concep-treated sorghum seed Use with Concep-treated seed only. only. seed Use Concep-treated with Do not plant fall cover crops. Do not plant not Do crops. cover fall plant not Do emergence rates below or use atrazine early or below use rates atrazine emergence crops other than corn in treated fields during fields treated in corn than other crops exists, use atrazine preemergence at pre- preemergence use atrazine exists, below. post as listed the same season. Thoroughly till soil before soil till Thoroughly season. same the treatments for average weed infestations. weed for average treatments if red is rice use Dual a problem, However, ppi and atrazine early post if needed. If if post early needed. ppi and atrazine pressure and morningglory cocklebur heavy planting any spring crop other than corn or corn than other crop spring any planting sorghum. Planting deeper than 1 inch will inch 1 than deeper Planting sorghum. increase safety margin. Do not use on coarse- on use not Do margin. safety increase textured soils (sand, loamy sand, sandy loam) sandy sand, loamy (sand, soils textured or on any soil with less than 1% o.m. For o.m. 1% than less with soil any on or atrazine All below. oil + AAtrex see soils, sandy labels have been revised because of surface of because revised been have labels and groundwater concerns. Special precau- Special concerns. groundwater and tions are required on new labels. new on required are tions Time Time Application of before planting. knockdown. Preplant for vegetation Same as above. top 2 inches within 14 days Incorporate thoroughly in preplant. Apply up to 45 days At planting. At planting. At planting. 7.64 EC 7.64 EC 32 oz/A. 1.3 qt/A. Atrazine 1 to 2 pt/A. Outlook 6 E 1 to 1.6 pt/A. 12 to 21 oz/A. formulations) Cinch 5.5 F ATZ Glyphosate (4 lb/gal Glyphosate (4 lb/gal Per Acre Broadcast Formulated Material formulations) + 2,4-D Bicep II Magnum 5.5 L or 1 qt/A 4L or 1 4L 1.1qt/A Nine-0. lb/A Dual Magnum 7.64 EC or Cinch Dual Magnum 7.64 EC or Cinch 32 oz/A + 1 pt/A of 4SL 2,4-D amine. 2,4-D 4SL of pt/A 1 + oz/A 32 Table 8-2. Recommended Table Herbicides for Control Weed in Grain Sorghum Weeds Weeds Controlled use ppi treatment above. Annual grasses and broadleaf weeds. Emerged weeds. Red rice, yellow nutsedge, For red rice or yellow nutsedge annual grasses and pigweed. annual grasses and pigweed. Red rice, yellow nutsedge, Annual grasses and pigweed. weeds. For red rice or yellow nutsedge, use Dual Magnum ppi above. Annual grasses and broadleaf Germinating annual grasses and grasses annual Germinating most annual broadleaf weeds, broadleaf annual most including cocklebur, annual cocklebur, including morningglory and sicklepod. and morningglory Active Chemical Per Acre Broadcast Crop, Situation, and -metolachlor @ 0.9 to -metolachlor @ 0.95 to -metolachlor + atrazine glyphosate + 2,4-D @ 1.0 + 0.50 lb/A glyphosate @ 1 lb/A glyphosate S 1.4 lb/A Preemergence dimethenamid @ 0.56 to 0.98 lb/A 1.9 lb/A S S @ 1.25 + 1 lb/A atrazine @ 1 lb/A UPDATED Preplant GRAIN SORGHUM 4-2015 7 UPDATED 4-2015 8

Table 8-2. Recommended Herbicides for Weed Control in Grain Sorghum (cont.)

Crop, Situation, and Active Chemical Formulated Material Method of Application Per Broadcast Acre Weeds Controlled Per Broadcast Acre Time of Application and Precautions

Preemergence [cont.]

saflufenacil @ 0.022 to Pigweed, velvetleaf, morning- Sharpen Burndown up to preemer- For best burndown results, tank mix with 0.044 lb/A glory and horseweed. 1 to 2 oz/A. gence. Do not apply Sharp- glyphosate or paraquat. An MSO and AMS en over the top of emerged must be used for burndown. sorghum. See label for further recommendations and restrictions.

dimethenamid + saflufenacil Annual grasses, pigweed, Verdict Burndown up to preemer- Rainfall or overhead irrigation is required for @ 0.31 to 0.62 + 0.044 to velvetleaf, morningglory and 10 oz/A. gence. Do not apply Verdict activation. Verdict can be used as a burn- 0.088 lb/A horseweed. over the top of emerged down that leaves behind residual control. grain sorghum. For best burndown activity, tank mix with glyphosate and use MSO 1 pt/A + AMS. On medium to fine soils, the rotation interval to soybeans is 30 days if you were to lose the grain sorghum crop. Use with Concep-treated seed. See label for restrictions.

dimethenamid For annual grasses and pig- Outlook 6E At planting. Use with Concep-treated seed only. Rates 0.56 to 0.98 lb/A weed. For red rice or yellow 12 to 21 oz/A. depend on percent organic matter. See nutsedge, use ppi treatment. label.

dimethenamid + atrazine Annual grasses and broadleaf Guardsman Max 5L At planting. Use with Concep-treated seed only. package mix weeds. For red rice or yellow 2.5 pt/A. nutsedge, use ppi treatment.

Postemergence 2,4-D amine @ 0.5 lb/A Most broadleaf weeds such as 2,4-D amine Apply when weeds are May be applied broadcast overtop to morningglory, cocklebur and 1 pt/A of 4 lb/gal 2,4-D amine. small and sorghum 6 to 12 sorghum not over 8 inches. Directed appli- sicklepod. Do not use a surfactant or oil. inches. cations later with drop nozzles. Do not treat when sorghum is in bloom. AVOID DRIFT. Do not apply during very active growth, i.e., when combination of good moisture, warm temperatures and high nitrogen exist, or excessive injury may result. Follow all State Plant Board regulations.

dicamba @ 0.25 lb/A Most broadleaf weeds such as Banvel or Clarity 4 SL From grain sorghum emer- Ground application only. Drift is extremely morningglory, cocklebur and 0.5 pt/A. gence up to 8 inches tall. toxic to soybeans. Do not apply after soy- sicklepod. Do not use a surfactant or oil. Best results on weeds beans begin to emerge in general area. Less 3 inches or less. toxic than 2,4-D to cotton. Follow all State Plant Board regulations. Follow all State all Follow Drift is extremely is Drift Do not apply more than Do not apply after soy- after apply not Do and Precautions Method Application of Plant Board regulations. regulations. Board Plant toxic to soybeans. to toxic cotton. to 2,4-D than toxic May be tank mixed with atrazine. See label. Best treatment for smartweed. Will not ALS-resistant control weeds. See crop rotation section for precautions about rotational crops. Do not apply to sorghum under stress from moisture or cold weather. Do not apply to sorghum that has been treated with an organophosphate insecticide at planting - emergence organo or within 15 days of a post phosphate insecticide application. Some injury may occur with higher rates on lighter soils. Same as above but may be used on sandy loam soil. Less likely to cause injury to milo or carryover to sensitive follow crops. Do not apply if grain sorghum is taller than 12 inches. Do not graze treated areas or feed forage from treated land within 21 days of appli- After cation. June 10, do not plant crops other than corn or grain sorghum the following year. Do not use on sands or sandy loam soils. For these soils, use atrazine and crop oil concentrate below. 2.5 active lb/A atrazine per season. soybeans. Best grass . Time Time Application of Apply to actively growing control obtained before inch. desired. control obtained before grass weeds exceed ½ inch. results on weeds 3 inchesor less. Less area. general in emerge to begin beans up to 8 inches tall. Best Same as above inches in height and before head emergence. grass weeds exceed ½ specific timing for weed for timing specific Apply from sorghum emer- Apply to emerged weeds. Aerial or ground Avoid drift application. to From sorghum emergence only. application Ground Postemergence. See label for label See Postemergence. Before sorghum reaches 6 oz/A. 1 oz/A. concentrate. 0.75 to 1 qt/A. Basagran 4 S Peak 57 WDG Yukon 67.5 Yukon DG mended on label. AAtrex, Atrazine AAtrex, AAtrex, Atrazine AAtrex, + nonionic surfactant. Per Acre Broadcast Formulated Material Crop Oil Concentrate Dual Magnum AAtrex + 0.8 to 1.4 + pt/A 1/2 qt/A. 12 inches tall. Best grass Permit or Halomax 75 WG 0.75 oz per Add acre. 0.25% sorghum between 5 and 20 1.5 lb/A 80W or 1.2 qt/A 4L or 1.33 or 4L qt/A 1.2 or 80W lb/A 1.5 lb/A Nine-0 + 1 qt/A oil concentrate. oil + 1 qt/A Nine-0 lb/A Add a nonionic surfactant or crop oil Weeds Weeds Controlled More effective on broadleafweeds. Good control of pigweed, annual cocklebur, morningglory, or 4L 1.1 to 2.2 Nine-0. lb/A Use lowvelvetleaf, spurred anoda, prickly beforesida, smartweed, sicklepod and weeds 1.25 to 2.5 80W exceedlb/A or 1 to 1½2 qt/A rate on silt loam soil and high rate on clay soil. No surfactant is recom- red rice. gence up to “close inchesin.”Apply in height. triazine-resistant biotypes. velvetleaf sida, prickly smartweed, nutsedge. yellow and weed and sicklepod. and weed and broadleaf weeds. and broadleaf hemp sesbania. Active Chemical Per Acre Broadcast Crop, Situation, and prosulfuron @ 0.027 lb/A Most broadleaf weeds including atrazine @ 1 to 2 lb/A Most small-seeded annuals. 0.75 to 1.3 + lb/A 1 to 1.2lb/A - smart velvetleaf, morningglory, halosulfuron @ 0.047 lb/A @ 0.047 halosulfuron nutsedge, flatsedge and Yellow + 0.075 0.2 lb/A atrazine @ 1.2 + lb/A oilconcentrate Same as above. bentazon @ 0.75 to 1 lb/A jimsonweed, ragweed, Cocklebur, S -metolachlor + atrazine @ annual pigweed, grasses, Annual halosulfuron + dicamba @+ dicamba halosulfuron nutsedge horseweed, Ragweed, UPDATED 4-2015

9 Expect some Expect Expect some Expect and Precautions Method Application of Weeds must be small. be must Weeds Weeds must be small. small. be must Weeds spray solution per acre. Can be tank mixed sodium chlorate. with tions. spray solution per acre. Can be tank mixed sodium chlorate. with not touch more than lower 3 inches of stalk. Some injury will occur. Tank mix with 1 atrazine lb/A for Tank improved control. Do not drift on cotton or tomatoes. spray solution per acre. Can be tank mixed sodium chlorate. with Directed spray with hoods. Spray must Use low rate on small weeds and higher rate on larger All weeds. atrazine labels have been revised because of surface and groundwater concerns. Special precautions are required on new labels. temporary burn. temporary Time Time Application of 7 days prior to harvest.to prior 7 days Coverage is important. Use 10 gallons of 7 to 10 days prior to harvest.to prior days 10 7 to Use a labeled brand and follow label direc- 3 days prior to harvest.to prior 3 days Coverage is important. Use harvest.to 10 prior gallons 7 days of Coverage is important. Use 10 gallons of Apply to weeds less than Apply prior to 12-inch grain sorghum. 2 inches tall. Postemergence to weeds in Use high rate on morningglories and pig- 30 inches tall, or flag leafemerges. atrazine. with mixed tank if injury temporary Apply on or after 3-leaf stage Use high rate on morningglories and pig- After sorghum is 12 inches. Postemergence from emer- Laddock . 2½ pt/A 1 oz/A. 1 oz/A. Huskie 6 lb/gal. Facet L Facet Aim 2 EC Aim surfactant. Buctril 2 E Buctril + Aim 2 EC Aim + 32 to 40 oz/A. oz/A. 40 to 32 22 to 32 oz/A. 32 to 22 formulations) 32 oz/A + 1 oz/A. + 1 oz/A. oz/A 32 Sodium Chlorate Sodium Basagran Atrazine + Per Acre Broadcast Formulated Material Paraquat (2 or 3 lb/gal 3 lb/gal or (2 Paraquat 90DF. Add crop oil concentrate. 90DF. mix with 0.5 lb/A active Atrazine. active lb/A 0.5 with mix 12.8 to 16 oz/A. Add 0.25% NIS. 0.25% Add oz/A. 16 to 12.8 until grain sorghum reaches weed. Several brands and trade names trade and brands Several Laddock = 0.5 to 0.5 a.i. lb/A rate. 32 or 21 oz/A. Add 0.25% nonionic 0.25% Add oz/A. 21 or 32 to 0.9 80W lb/A or 0.55 to 0.8 lb/A Package mix is 1 to 1½1 to tank weeds, larger On pt/A. seedling (2- to 4-leaf) stage. weed. available. 2 gal of 3 lb/gal or 1 gal of 1 gal or 3 lb/gal of 2 gal available. Glyphosate (4 lb/gal formulations) lb/gal (4 Glyphosate Glyphosate (4 lb/gal formulations) lb/gal (4 Glyphosate 1 to 1.5 + pt/A 1 to or 1.5 4L 0.6pt/A gence to boot. Weeds Weeds Controlled Table 8-2. Recommended Table Herbicides for Control Weed in Grain Sorghum (cont.) morningglories. weeds. weeds. glories and pigweed. pigweed. and glories Annual grasses and broadleaf and grasses Annual Active Chemical Per Acre Broadcast Crop, Situation, and glyphosate + carfentrazoneglyphosate lb/A + 0.016 @ 1 lb/A vines/ of desiccation Improved Preharvest sodium chlorate @ 4.5 to 6lb/A vegetation. green of Desiccation carfentrazone @ 0.016 lb/A @ 0.016 carfentrazone morningglories. of Desiccation lb/A @ 1.3 1 to glyphosate vegetation. green of Desiccation quinclorac @ 0.25 to 0.375 broadleaf and grasses Annual lb/A bromoxynil @ 0.25 to 0.375 morning- smartweed, Cocklebur, lb/A bromoxynil + pyrasulfotole pig- to 0.39 lb/A including broadleaves Annual paraquat @ 0.5 lb/A @ 0.175 to 0.22 + lb/A 0.03 morningglories. and weed Postemergence [cont.] bentazon + atrazine @ 0.5 weeds. broadleaf Most to 0.75 + 0.5 to 0.75 lb/A UPDATED 4-2015 10 Figure 8-6. Common Weed Seedlings in Grain Sorghum smooth pigweed, redroot pigweed common cocklebur

Palmer amaranth

tall waterhemp ivyleaf morningglory

common lambsquarters

UPDATED 4-2015 11 Figure 8-6. Common Weed Seedlings in Grain Sorghum (cont.) pitted morningglory smallflower morningglory

palmleaf morningglory

bigroot morningglory entireleaf morningglory

purple moonflower

12 UPDATED 4-2015 spotted spurge large or southern crabgrass

prickly sida

Pennsylvania smartweed goosegrass

nutsedge

UPDATED 4-2015 13 Figure 8-6. Common Weed Seedlings in Grain Sorghum (cont.) broadleaf signalgrass fall panicum red rice

barnyardgrass johnsongrass

14 UPDATED 4-2015