Publication #SS-AGR-01

Topics: Agronomy | Weed Management for Tobacco | Weed Management in Field Crops and Pasture Grasses (WMG) | Tobacco | Field and Forage Crops | Moore, J Michael

Weed Management in Tobacco¹

J. Michael Moore²

Weed control is an important production practice in tobacco since weed competition for moisture and nutrients may result in yield losses. In addition to reduced yields, weeds may also be a serious source of foreign material in mechanically harvested tobacco. Good weed control in tobacco is best achieved by utilizing all available methods of weed control in an integrated program.

Sanitation

Many of the problem weeds in tobacco are the result of seed produced in the field during the preceding crops or seed blown into the field or onto plant beds from adjacent areas such as fence rows or ditch banks. Preventing weeds from producing seed in these areas may aid in reducing weed problems in succeeding tobacco crops. Destroying weeds around the plant bed area as well as utilizing natural or artificial windbreaks will reduce weed problems. Remember that fumigation leaves no residual for weed control. Thus, do not recontaminate fumigated beds with weed-infested soil that may adhere to shoes or equipment. Also, weeds that grow in fence rows and surrounding areas may harbor aphids, thrips, or other insects and viruses that may attack tobacco.

Crop Rotation

The benefits of crop rotation on reduction of diseases, insects, and nematodes have been well documented. In addition, crop rotation may also be important for reducing weed problems. Many weeds, especially the large seeded broadleaf weeds such as sicklepod, cocklebur, and Florida beggarweed, can be more effectively controlled in other crops such as corn or sorghum. Controlling these weeds in a rotational crop reduces the weed seed available for germination in the tobacco crop.

Residues of some herbicides used in preceding crops are a potential problem, as tobacco is highly sensitive, and this potential should be considered when choosing the herbicide. Label restrictions on rotational crops should be followed.

Weeds may be hosts for certain insects, diseases, and nematodes, and weeds allowed to grow in the field prior to tobacco may result in increased pest problems.

Cultivation

Cultivation and occasional hand-hoeing have, and continue to be, an important part of a tobacco weed control program. Currently, there are several weeds in tobacco that can be effectively controlled only by this method. In addition, proper cultivation may aid in better drainage and protection from flooding, a better root system and less lodging, and more efficient mechanical harvesting.

Chemical Control

The use of herbicides in tobacco has become widely accepted by growers and offers several important benefits that supplement other components of the weed management program.

Good early-season weed control with herbicides can be extremely important in reducing competition and allowing the rapid establishment of tobacco, resulting in more effective cultivation. Labor requirements for hand-hoeing and cultivation can be reduced by proper use of herbicides. Herbicides may supply some insurance against fields becoming weedy during wet periods following transplanting. All weeds do not respond the same to all herbicides; therefore, the weeds expected in the field should be known when planning a weed control program. The next step is to select the herbicide or combination of herbicides most effective on the anticipated weeds (Table 2). After selecting the herbicide program needed, refer to Table 1 for proper rates, time of application, and application procedures. Table 1 and Table 2 are based on current available research from IFAS and other southeastern states; however, for more detailed information on the use of each herbicide, read the label.

Tables

Table 1.

Weed management in tobacco.

Trade Name and Broadcast Rate/Acre of Commercial Product	Common Name and Broadcast Rate/Acre of Active Ingredient	Remarks
TOBACCO PLANT BEDS
Methyl bromide + Chloropicrin (several brands and formulations)	methyl bromide + chloropicrin rate depends on formulation	Treat when the soil is moist and when temperatures are above 55°F. Inject 6–8" deep with chisels spread 10–12" apart or release with applicator under plastic film. Leave for 48 hours, then remove cover and aerate for 48–72 hours (2 weeks for 75:25 methyl bromide: chloropicrin). Controls most weeds except some hardseeded legumes. Also controls nematodes and soilborne insects and diseases.
Poast (1.0 pt) + Crop Oil Conc. (2.0 pt)	sethoxydim (0.188 lb)	Poast may be applied to plant beds only with ground equipment for the control of emerged annual grasses. Volume should be 5–20 GPA and a crop oil concentrate should be added at a rate of 2 pt/A. Do not cover beds until spray material has dried. See label for further precautions.
TOBACCO FIELDS PREPLANT
Prowl 3.3EC (1.8 - 2.4 pt) Prowl H₂0 (2.0 - 2.5 pt)	pendimethalin (0.75 - 1.0 lb)	Apply and incorporate to a depth of 2–3". If applying before bedding, incorporate with a power-driven tiller set to operate 2–3" deep or with a disk harrow set to cut 4–6" deep. If a disk is used, a second disking at a right angle will improve results. If applying after beds are formed, incorporate with a power-driven tiller to a depth of 2–3".
Command 3ME (2.0 - 2.7 pt)	clomazone (0.75 - 1.0 lb)	Apply in a minimum of 20 gal of water per acre up to 30 days before transplanting. May assist with grass and small-seeded broadleaf control. May be mixed with other PPI tobacco herbicides. Consult label to avoid off-target drift problems. May also be applied immediately after transplanting up to 7 days after transplanting, but prior to weed emergence.
Devrinol 2EC (2 - 4 qt) or Devrinol 50DF (2.4 lb)	napropamide ¹ (1.0 - 2.0 lb)	Use lower rates on sandy soils.
POST-TRANSPLANT
Devrinol 2 EC (2 - 4 qt) or Devrinol 50DF (2.4 lb)	napropamide ² (1.0 - 2.0 lb)	Apply over top of transplants. If application is delayed several days after transplanting, tillage will be needed to destroy previously germinated weeds. If rainfall is not received within 3–4 days, apply 1/2" of irrigation water to move the herbicide into the zone of weed seed germination.
Command 3ME (2.0 - 2.7 pt)	Clomazone (0.75 - 1.0 lb)	Apply in a minimum of 20 gal of water per acre, immediately or up to 7 days after transplanting, but prior to weed emergence. If weeds have emerged, cultivate shortly before or at the time of treatment. Do not apply post-transplant if a preplant application was made.
Poast (1.5 pt) + Crop Oil Conc. (2.0 pt)	sethoxydim (0.282 lb)	Poast may be applied 3 weeks after transplanting and until 7 weeks after transplanting with ground equipment for the control of emerged annual grasses. Volume should be 5–20 GPA and a crop oil concentrate should be added at a rate of 2 pt/A.
LAY-BY
Prowl 3.3 EC (1.2 - 1.8 pt) Prowl H₂0 (2.0 - 2.5 pt)	pendimethalin (0.5 - .75 lb)	Apply with drop nozzles to the row middles following the lay-by cultivation. If rainfall is not received within 3–4 days, apply 1/2" of irrigation water to move the herbicide into the zone of weed seed germination. Do not spray in the bud of tobacco plants. Do not plant any root crop for 12 months after application.
Devrinol 2 EC (2 - 4 qt) or Devrinol 50DF (2.4 lb)	napropamide ² (1.0 - 2.0 lb)	Similar remarks as for Prowl lay-by above.
POST DIRECTED AFTER FIRST HARVEST
Aim EC (2 lb ai/gal) 0.8 - 1.5 fl oz	carfentrazone (0.013 - 0.023 lb ai)	Aim EC may be applied with drop nozzles or other spray equipment capable of directing the spray to the target weeds and away from sensitive plant parts. Aim EC may be applied up to the maximum rate for the target crop for the control of larger weed sizes or weeds not controlled with lower use rates. Directed spray after first priming (Flue-Cured Tobacco Only) Aim EC may be applied as a directed spray application after the first priming in only flue cured tobacco only for the control of emerged and actively growing broadleaf weeds. Directed spray equipment should position nozzles a minimum of 3 to 4 inches above the soil, with nozzles directed underneath the crop canopy. Spray solution should be directed at the base of tobacco plants for minimal contact with foliage while maintaining maximum contact with broadleaf weeds that are at appropriate treatment size. Do not apply when conditions favor drift or wind is above 10 mph. Use Aim EC for postemergence control of many broadleaf weeds (including most morningglory species other than small flower) up to 4 inches high growing in between the rows of tobacco. Use higher rates when treating more mature weeds or dense vegetative growth. COVERAGE IS ESSENTIAL FOR GOOD CONTROL. Use adequate spray volume to achieve thorough coverage.
¹ See labels for tank-mixes with other pesticides or fertilizers. ² The following crops may be injured if planted within 12 months of Devrinol application; alfalfa, small grains, sorghum, corn, lettuce, sugarbeets. The total napropamide applied in a season should not exceed 2 lb active ingredient per acre.

Trade Name and Broadcast Rate/Acre of Commercial Product

Common Name and Broadcast Rate/Acre of Active Ingredient

Remarks

TOBACCO PLANT BEDS

Methyl bromide + Chloropicrin (several brands and formulations)

methyl bromide + chloropicrin

rate depends on formulation

Treat when the soil is moist and when temperatures are above 55°F. Inject 6–8" deep with chisels spread 10–12" apart or release with applicator under plastic film. Leave for 48 hours, then remove cover and aerate for 48–72 hours (2 weeks for 75:25 methyl bromide: chloropicrin). Controls most weeds except some hardseeded legumes. Also controls nematodes and soilborne insects and diseases.

Poast

(1.0 pt)

Crop Oil Conc.

(2.0 pt)

sethoxydim

(0.188 lb)

Poast may be applied to plant beds only with ground equipment for the control of emerged annual grasses. Volume should be 5–20 GPA and a crop oil concentrate should be added at a rate of 2 pt/A. Do not cover beds until spray material has dried. See label for further precautions.

TOBACCO FIELDS

PREPLANT

Prowl 3.3EC

(1.8 - 2.4 pt)

Prowl H₂0

(2.0 - 2.5 pt)

pendimethalin

(0.75 - 1.0 lb)

Apply and incorporate to a depth of 2–3". If applying before bedding, incorporate with a power-driven tiller set to operate 2–3" deep or with a disk harrow set to cut 4–6" deep. If a disk is used, a second disking at a right angle will improve results. If applying after beds are formed, incorporate with a power-driven tiller to a depth of 2–3".

Command 3ME

(2.0 - 2.7 pt)

clomazone

(0.75 - 1.0 lb)

Apply in a minimum of 20 gal of water per acre up to 30 days before transplanting. May assist with grass and small-seeded broadleaf control. May be mixed with other PPI tobacco herbicides. Consult label to avoid off-target drift problems. May also be applied immediately after transplanting up to 7 days after transplanting, but prior to weed emergence.

Devrinol 2EC (2 - 4 qt)

Devrinol 50DF (2.4 lb)

napropamide ¹

(1.0 - 2.0 lb)

Use lower rates on sandy soils.

POST-TRANSPLANT

Devrinol 2 EC

(2 - 4 qt)

Devrinol 50DF

(2.4 lb)

napropamide ²

(1.0 - 2.0 lb)

Apply over top of transplants. If application is delayed several days after transplanting, tillage will be needed to destroy previously germinated weeds. If rainfall is not received within 3–4 days, apply 1/2" of irrigation water to move the herbicide into the zone of weed seed germination.

Command 3ME

(2.0 - 2.7 pt)

Clomazone

(0.75 - 1.0 lb)

Apply in a minimum of 20 gal of water per acre, immediately or up to 7 days after transplanting, but prior to weed emergence. If weeds have emerged, cultivate shortly before or at the time of treatment. Do not apply post-transplant if a preplant application was made.

Poast

(1.5 pt)

Crop Oil Conc.

(2.0 pt)

sethoxydim

(0.282 lb)

Poast may be applied 3 weeks after transplanting and until 7 weeks after transplanting with ground equipment for the control of emerged annual grasses. Volume should be 5–20 GPA and a crop oil concentrate should be added at a rate of 2 pt/A.

LAY-BY

Prowl 3.3 EC

(1.2 - 1.8 pt)

Prowl H₂0

(2.0 - 2.5 pt)

pendimethalin

(0.5 - .75 lb)

Apply with drop nozzles to the row middles following the lay-by cultivation. If rainfall is not received within 3–4 days, apply 1/2" of irrigation water to move the herbicide into the zone of weed seed germination. Do not spray in the bud of tobacco plants. Do not plant any root crop for 12 months after application.

Devrinol 2 EC (2 - 4 qt)

Devrinol 50DF

(2.4 lb)

napropamide ²

(1.0 - 2.0 lb)

Similar remarks as for Prowl lay-by above.

POST DIRECTED AFTER FIRST HARVEST

Aim EC

(2 lb ai/gal)

0.8 - 1.5 fl oz

carfentrazone

(0.013 - 0.023 lb ai)

Aim EC may be applied with drop nozzles or other spray equipment capable of directing the spray to the target weeds and away from sensitive plant parts. Aim EC may be applied up to the maximum rate for the target crop for the control of larger weed sizes or weeds not controlled with lower use rates.

Directed spray after first priming (Flue-Cured Tobacco Only) Aim EC may be applied as a directed spray application after the first priming in only flue cured tobacco only for the control of emerged and actively growing broadleaf weeds. Directed spray equipment should position nozzles a minimum of 3 to 4 inches above the soil, with nozzles directed underneath the crop canopy. Spray solution should be directed at the base of tobacco plants for minimal contact with foliage while maintaining maximum contact with broadleaf weeds that are at appropriate treatment size. Do not apply when conditions favor drift or wind is above 10 mph.

Use Aim EC for postemergence control of many broadleaf weeds (including most morningglory species other than small flower) up to 4 inches high growing in between the rows of tobacco. Use higher rates when treating more mature weeds or dense vegetative growth. COVERAGE IS ESSENTIAL FOR GOOD CONTROL. Use adequate spray volume to achieve thorough coverage.

¹ See labels for tank-mixes with other pesticides or fertilizers.

² The following crops may be injured if planted within 12 months of Devrinol application; alfalfa, small grains, sorghum, corn, lettuce, sugarbeets. The total napropamide applied in a season should not exceed 2 lb active ingredient per acre.

Table 2.

Estimated effectiveness of herbicides on common weeds in Florida tobacco¹.

WEEDS	Herbicides
	Prowl	Command	Devrinol	Poast	Prowl
Time of Application	PPI	PPI or PT	PT or LB	POST	LB
ANNUAL GRASSES
Crabgrass	E	E	E	E	E
Goosegrass	E	E	E	E	E
Sandbur	E	E	G-E	E	E
Crowfootgrass	E	E	E	E	E
Texas panicum	G-E	G	--	G	G-E
ANNUAL BROADLEAVES
Florida pusley	E	F	G-E	P	E
Pigweed (redroot & spiny)	G	F	G-E	P	E
Lambsquarter	E	F	G-E	P	E
Morningglories	P	P	P	P	P
Sicklepod (coffeeweed)	P	P	P	P	P
Florida beggarweed	P	P	P	P	P
Cocklebur	P	P	P	P	P
PERENNIALS
Nutsedge	P	P	P	P	P
Bermudagrass	P	P	P	P	P
¹Estimated effectiveness based on herbicide rates recommended in this report. Effectiveness may vary depending on factors such as herbicide time of application, soil type, and weather conditions. Time of Application PPI = Preplant Incorporated PT = Post Transplant LB = Lay-by Weed Control Symbols E = 90%–100% control G = 80%–89% control F = 60%–79% control P = Less than 60% control -- = insufficient observations

Footnotes

This document is SS-AGR-01, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date January 2000. Revised March 2013. Visit the EDIS website at http://edis.ifas.ufl.edu.

J. Michael Moore, professor and tobacco Extension agronomist, Crop and Soil Sciences, University of Georgia, working under cooperative agreement with the Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611. (The original version of this publication was written by J. Tredaway Ducar and revised in 2013 by J. A. Ferrell.)

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, Dean.

Weed Management in Tobacco1

Sanitation

Crop Rotation

Cultivation

Chemical Control

Tables

Footnotes

Weed Management in Tobacco¹