Crop Profile for Tobacco in Kentucky

Prepared: October, 1999
Revised: June, 2003

Cultural Practices

Tobacco has historically been one of Kentucky’s most important crops. Although tobacco acreage has steadily decreased over the last 50 years, it is still an important income crop for many Kentucky farmers (Figure 1). Tobacco is started by seeding in late February, in greenhouses and conventional beds. Transplanting to fields begins in early May. The varieties most planted in Kentucky are TN 90, 14XL8, NC BH129, Hybrid 403, and TN 86. Harvest is done between August and the first or second week of October. Yields vary from 2000 to 3500 pounds per acre.

Worker Activities

Tobacco production is a labor intensive enterprise that requires about 180 hours per acre (Gross et al. 2001).

Transplant Production

Most transplant production occurs in a float system where tobacco seeds are placed into individual cells in styrofoam trays (about 240 cells/tray) with an appropriate soil-less media. The trays are floated on indoor or outdoor water beds. Fungicide and insecticide applications are made to the plants as recommended. Time requirement is about 5 hours per acre.

Land preparation, plowing of sod or cover crop, disking, and final tillage typically takes 3 hours and is performed by a person in an unenclosed cab tractor. Transplants are set in the field with a mechanical or carousel-type transplanter. This operation requires about 13 hours and each plant is handled by a person riding on the equipment. An average of 10 hours is spent in cultivation. Spraying of insecticides, herbicides, fungicides, or plant growth regulators requires about 3.5 hours per acre. The growth regulator is applied after topping, which is the manual removal of the flowering structures of the plant. It takes about 3 hours to top an acre of tobacco and another 3.2 hours to drop the sticks on which the harvested crop will be hung in the barn for curing.

It takes about 40 hours of labor to manually cut each stalk, place it on a stick and ultimately transport and hang the crop in a curing barn. This is done about 4 weeks after the top is removed from each plant. After curing, the tobacco is removed from the barn (4.8 hours) and the leaves removed or stripped from the stalk by hand. (80 hours). Clean up requires about 11 hours. Disking of the field and sowing of cover crop requires about 0.7 hours per acre.

Figure 1. Current and historical tobacco production statistics for Kentucky. (KY Ag. Statistics 2000-2001)



Insect Pests

Table 1. Pounds of Insecticide Active Ingredient Sold in Kentucky from 1992 – 2001. (KY Division of Pesticides sales data)

Insecticide

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Organophosphate

acephate

259339

259826

240172

210855

232826

234557

237862

192497

157489

135255

chlorpyrifos

24133

23564

30531

27197

36915

63307

33020

27707

33233

22148

diazinon

10988

7418

8175

3572

5664

3887

3078

3556

1970

1282

disulfoton

15759

22658

9057

16104

15049

11307

17586

7434

9520

5612

fonofos

5269

18032

10172

7589

5221

270

677

0

12

0

malathion

17564

11587

15248

18708

13280

12847

16480

10330

1055

483

methyl parathion

450

726

262

220

912

0

270

48

0

0

Carbamate

carbaryl

606

3706

19

112

24

63

67

288

0

0

carbofuran

20492

10385

4159

3803

1025

240

0

48

0

435

methomyl

500

547

809

663

207

327

262

300

20

152

oxamyl

1870

1143

1426

1057

1066

630

736

404

21

10

Chloronicotinyl

imidacloprid

0

0

0

0

0

5406

10287

11941

13908

9372

Organochlorine

endosulfan

129139

114203

107344

77536

104969

103325

103467

85859

66705

45517

lindane

1900

1137

1676

774

1305

630

4286

3198

20

13

spinosyn AD

0

0

0

0

0

0

0

387

1010

388

Biological

Bacillus thuringiensis

17593

1281

1925

1139

2691

1437

3783

3232

4250

3970

Total

505602

476213

430975

369329

421154

438233

431861

347229

289213

224637


Aphids
Myzus nicotianae

The tobacco aphid is a soft-bodied insect that is found in clusters on the underside of tobacco leaves. There are two color forms of the aphid, red and green. The red form replaced the green as the predominant form in the late 1980's. The 1/16 in long 'plant lice' use their sucking mouthparts to remove sap from plants. Feeding by large numbers of aphids results in light weight leaves that may ripen prematurely. The sugar rich 'honeydew' excreted by aphids builds up on the leaf surface and supports growth of black, sooty mold. The honeydew may cause leaves to stick together and cure to a dark, off color of poor quality. Tobacco aphids may transmit viruses such as tobacco vein mottling virus though their mouthparts.

Aphid populations build up after winged females fly into tobacco fields, usually during the middle portion of the growing season. They settle on the leaf to feed and give birth to living young. Large populations can build up in a short period of time due to their short life cycle and occurrence of several generations during the growing season.

Aphids attack 100% of tobacco fields in Kentucky every year, causing a yield loss of about 5 - 10%.


Controls

Biological
Lady beetles (various species) are important predators of aphids. Both adults and larvae prey on aphids. Syrphid fly larvae (Allograpta obliqua) also feed on aphids, sucking out their body fluids.

Cultural
Keep area around the plant beds (100 feet or more) free of plant trash and weeds that can harbor overwintering aphids. Consider planting early and do not exceed recommended nitrogen rates.

Chemical

* restricted use.


Cutworms
Agrotis ipsilon

Cutworms are generally dingy gray to dark brown or black. Faint longitudinal stripes may occur on the body. Full grown larvae range from 1 to 1 ½ in. long. Infestations are likely to occur in tobacco following sod, or in fields with an abundance of winter annual weeds prior to tillage. Larvae feed for four to five weeks and can reduce stands by cutting off newly set transplants. Cutworms feed at night and can be found in the soil around freshly cut plants during the day. They curl up when disturbed. Cutworms may be very damaging in tobacco beds. Damage often appears first along weedy margins or portions of the bed lying along fences. Cutworms overwinter in the soil as brown pupae and there is one generation per year.Cutworms occur yearly and about 20% of the tobacco fields in Kentucky are attacked.

Controls

Cultural
Prepare the soil four to six weeks before transplanting.

Chemical


Slugs
Limax spp.

Slugs may be very damaging in plant beds, especially during cool, rainy springs. Slugs are shell-less snails. They have soft, legless, unsegmented bodies which vary from light yellow to gray-brown. The elongated body acts as a muscular foot that glides along on a mucous secretion which gives slugs their slimy appearance. Slugs feed at night, tearing ragged holes in the leaves with their rasplike mouthparts. Feeding damage and silvery slime trails may be the only clues to their presence because slugs hide under debris during the day.

Controls

Chemical


Flea Beetles
Epitrix hirtipennis

The adult flea beetles chew small, rounded holes into or through the leaves, especially from the underside. They attack the young plants in the seedbeds almost as soon as they come up and occasionally cause significant damage. The greatest damage is done after the plants are transplanted. Following mild winters they weaken or kill newly set transplants. The larvae feed on the roots of tobacco and may cut off the small roots.

Adults are brownish, hard-shelled beetles, 1/16 in long. Adults overwinter under leaves, grass, and trash on the ground about tobacco fields, especially along the margins of woods. There are usually three generations a year.

Flea beetles attack 100% of the tobacco fields in Kentucky, causing a yield loss of about 1%.

Controls

Cultural
Keep areas around the plant beds (100 feet or more) free of plant trash and weeds that can harbor overwintering beetles. Destroy beds as soon as possible so they do not become a breeding ground. Flea beetles from undestroyed beds often invade nearby fields.

The ground surrounding the seedbed should be burned over in late winter. Less injury will occur if the seedbeds are located as far from overwintering sites as possible and at a considerable distance from the new fields. Seedbeds should be boarded or planked on the sides and covered with tobacco cloth having at least 25 strands to the inch, making the covering beetle tight. Surrounding the seedbed should be a 2 or 3 ft strip of early-seeded tobacco, protected with poles and cloth and kept dusted or sprayed with chemicals. The top soil of seedbeds should be sterilized or fumigated before planting. Old seedbeds should be plowed and harrowed after transplanting. After the crop is harvested, much can be done to check flea beetles by destroying the stalks and the 'suckers' that grow up in the fields.

Chemical

* restricted use.


Green June Beetles
Cotinis nitida

Green June beetle larvae are rarely pests in tobacco plant beds. Eggs are laid during the summer. Larvae hatch and grow to be about two in. in length. They have a brown head and creamy white C-shaped bodies. Green June beetles overwinter in the larval stage, complete their development the following spring, and are nearly full grown when beds are started . Larvae live several inches below the soil surface and cause some damage by feeding on younger tender roots of plants. They cause the most serious damage by their continual burrowing and tunneling, loosening the soil and uprooting plants. Their eggs are laid in soil rich with decaying vegetable matter, on which the grubs feed until cold weather. There is one generation each year.

Green June beetles seldom attack tobacco fields in Kentucky (less than 1% of the fields) and there is no yield loss.

Controls

Chemical


Wireworms
many species of the order Coleoptera, family Elateridae

Wireworms are among the most difficult insects to control. The crop may start well and later become thin and patchy because the worms bore into the underground part of the stem causing the plant to wither and die, though they do not cut it off completely. Wireworm larvae are usually hard, dark brown, smooth, wire-like worms, varying from ½ to 1 ½ in. in length when grown. Some species are soft, and white or yellowish in color. Injury is usually most severe to crops planted on sod ground, or the second year after sod. The winter is passed mainly in the larval and adult stages in the soil. There is much overlapping of the generations so that all stages and nearly all sizes of larvae may be found in the soil at one time.

Wireworms attack about 1% of the tobacco fields in Kentucky, causing yield loss of less than 1%.

Controls

Cultural
Shallow tillage to prevent the growth of all vegetation, especially large weeds, in the early part of the summer, and the avoidance of deep plowing which allows the wireworms to penetrate into the soil more successfully are recommended. On the other hand, plowing to a depth of 9 in. about the first of August and allowing the dry lumpy soil to lie undisturbed for a few weeks may to kill great numbers of pupae and adults by breaking up their cells in the soil. Hay crops or long-standing pasture or grain crops are favorable to wireworms and should be omitted as much as possible from the rotation. Certain species of wireworms are abundant only in poorly drained soils. Proper draining will prevent damage by these species.

Chemical


Budworms
Heliothis virescens

The tobacco budworm is one of the most destructive pests of tobacco. Eggs, laid on tobacco leaves, hatch and eventually develop into 1 ½ in. long larvae when full grown. The larvae are light to dark green and have several longitudinal pale stripes. They may chew small holes in the leaves before they reach the buds. Larvae then damage the bud or growing tip of the plant. They may appear any time during the growing season. The leaves that expand from the buds are often ragged and distorted. Because of their protected location on the plant, budworms are difficult to control. The pupal stage is passed in the soil at a depth of 1 to 4 in.

Controls

Biological
The wasp Campoletis sonorensis and the tachinid flies Zygostrumia spp and Winthemia spp belong to a large family of important parasitic flies. Stilt bugs Jalysus wickhami, feed on budworm eggs.

Cultural
Deep plowing and cultivating the soil in fall and winter are effective in turning up the pupae and exposing them to natural enemies and weather. Consider a budworm-tolerant variety and avoid excessive nitrogen fertilization. Timing planting date: early planted tobacco is usually more attractive to budworms. Top fields at 50% button. Flowers attract egg-laying moths and are an excellent food source, promoting development of the next generation.

Chemical

This caterpillar is resistant to organophosphates, carbamates, and pyrethroids.

* restricted use.


Tobacco Hornworms
Manduca sexta

Hornworms infest plants all summer long and can ruin many leaves and where abundant, defoliate the plants. Because of their concealing coloration, they can often be located most easily by the pellets of excrement which they drop on leaves or the ground, above which they are feeding. They chew irregular holes in leaves and often feed along leaf margins. Newly hatched larvae are 1/4 in long, pale green with a large horn at the posterior end. Larger larvae (up to 4 in) are bright green in color. They have seven white diagonal stripes on each side and a curved red horn. The adult, a dark gray moth has six round, orange-yellow spots on each side of the abdomen. The overwintering pupae are very often spaded up or plowed out in the spring. There are 2 generation annually.

Hornworms attack 50% of tobacco fields in Kentucky every year causing a yield loss of 2 to 5%.

Controls

Biological
The braconid wasp, Apanteles congregatus, is an important parasite, and the spined stiltbug, Jalysus spinosus, is an egg predator. Tachinid flies and the paper wasp (Polistes spp. and others) also prey on hornworm larvae.

Cultural
Where labor is cheap and plentiful, hand picking of these worms is fairly effective, and laborers should always be instructed to destroy the worms whenever they are encountered while working among the plants. Fall and winter plowing to destroy the pupae, where it is not otherwise objectionable, reduces the population of hornworms the following season. Stalks and stubble should be destroyed immediately after harvest.

Chemical

* restricted use.


Stink Bugs
Euschistus servus and Euchistus variolarius

Stink bugs are gray-brown, shield-shaped bugs slightly over ½ in. long when full grown. Nymphs are similar to adults and lack wings. Their beak-like mouthparts are used to remove plant sap. A salivary secretion, which is injected as the insect feeds, produces a rapid wilting of the leaf or stem. The leaf usually resumes its normal shape and is not permanently damaged. Scalded areas may develop on injured leaves during hot weather. Growers are likely to encounter injury symptoms and not see the insects. Damage is usually limited to scattered plants, often in border rows.

The adults overwinter in woods and fence rows and in plant debris, and feed during April and May on berries of dogwood and elder. There are typically two generations per year.

Control

Biological
Dipterous parasites, including Trichpoda pernipes, Cylindromyia euchenor, Euthera tetranix, and Gymnosoma fuliginosum, attack the adults of the stink bug. Egg parasites, Ooencyrtus, Trissolcus, and the Telenomus spp. are also effective.

Chemical


Grasshoppers
Melanoplus femurrubrum, M. bivittatus and M. differentialis

Grasshoppers chew irregular holes between veins of leaves. Most species prefer other plants but will eat tobacco if their food supply is inadequate. Grasshoppers often migrate into tobacco fields from ditch banks and grasslands, especially when populations are high during droughts and following hay mowing or other habit modifications. Tobacco injury usually starts along the edges of fields and is more common late in the growing season.

The young hoppers differ little from the adult, except in size and lack of wings. There are usually 5 or 6 nymphal instars that require 40 to 60 days to reach the adult stage and growth is completed from the middle of August to the first of September. The adults, however, continue to feed until the first heavy frost. They overwinter in the egg stage and one generation is produced per year.

Grasshoppers attack about 5% of the tobacco fields in Kentucky causing a yield loss of 1%.

Controls

Biological
The microsporidian Nosema locustae is approved as a biological control agent in grasshopper baits, and the fungi Beauvaria bassiana and Entomophthora grylli are suppressive. Important natural enemies include anthomyiid and bombyliid fly egg parasites, blister beetles, and ground beetles.

Cultural
In order to destroy the eggs, plow or disk of areas in which grasshoppers have laid their eggs, exposing them to the action of the weather and to birds during the winter or early summer.

Chemical



Weeds

Preface

Weeds are present in all agricultural production fields. Rarely are weeds controlled on an individual basis. Weed management strategies are typically aimed at a broad spectrum of species. In a given year, there will commonly be a few predominant weed species present in any given field, with numerous other species present at levels that do not have a significant impact on production and yield. However, weed populations are dynamic and opportunistic. Species composition can change rapidly in response to changes in production and management practices. As a result, there will always be weeds present that will compete with the crop. As with many other major Kentucky crops, weed management is a dynamic issue. Beyond the obvious issue of pest presence, a farmer’s decisions are also strongly impacted by costs.

Creation of a good field management history is central to making decisions to address the weed population present during any specific year. The high investment associated with tobacco production needs to be supported by a balance involving intelligent cultural practices and modest chemical weed control practices.

Because weed management is seldomly focused around the control of a single species, this section of the tobacco crop profile will be structured differently than the insect and disease sections. Herbicide options for individual species will be listed after the weed species. The other control practices will be discussed once because they will be similar for most weeds. As stated before, weeds are not managed on an individual basis in tobacco production and listing specific control measures for specific species is not representative of actual production practices.

Fumigation Controls: Methyl bromide and metam-sodium are soil fumigants that are used to sterilize the soil before seeding tobacco plant beds. The primary target is ungerminated weed seeds, however these fumigants also kill plant pathological agents harbored in the soil. This practice has been an important component of tobacco production for many years, however the switch to a float bed system to germinate tobacco seed has been the primary reason for decreased fumigant use. Label restrictions imposed by the EPA and declining acreage have also had an impact on decreased usage. Producers continue to search for alternative control measures to help reduce weed and disease pressure, but these products are still an important tool for sterilizing the plant float beds that are used to start growing the tobacco seedlings.

Table 3. Pounds of Fumigant Active Ingredient Sold in Kentucky from 1992 – 2001. (KY Division of Pesticides data)

Fumigant

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Methyl bromide

1045137

852462

664270

426741

398049

577809

277420

172276

77516

66132

Metam-sodium

16486

24381

12640

17968

10067

552

1421

1857

9117

43

Total

1061623

876843

676910

444709

408116

578361

278840

174133

86633

66175


Tobacco Growth Regulators: Maleic hydarazide and fatty alcohol are growth regulators used to control tiller or "sucker" growth. Removing the tops of tobacco eliminates the dominant influence of the terminal shoot over lateral shoots or suckers. If left uncontrolled, these extraneous tobacco growths can reduce plant yield by diverting plant energy into these structures rather than into the primary leaves. Manual control of suckers has almost totally given way to less expensive and more efficient chemical control.

Table 4. Pounds of Growth Regulator Active Ingredient Sold in Kentucky from 1992 – 2001. (KY Division of Pesticides data)

Growth Regulator

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Maleic hydrazide

352782

353986

615018

504349

610776

670110

689460

528541

338579

363315

Fatty alcohol

177729

182841

218593

259063

302171

312372

375308

315484

326983

301324

Total

530510

536827

833611

763411

912948

982482

1064768

844025

665562

664638


Alternative Controls: There are no alternative control measures for weed control in Kentucky tobacco.

Cultural Control Practices: Tillage is an important component of weed control and field preparation in tobacco. The majority tobacco ground is tilled in some manner to prepare a favorable plant setting environment. After setting, interrow cultivation is often an important component of an integrated weed control program. The number of cultivation events in a growing season will vary from grower to grower, ranging from no cultivation in no-till tobacco fields (very small proportion) to multiple cultivations for control of multiple weed emergence events. Proper cultivation should be shallow, as to not bring weed seed to the soil surface and to conserve soil moisture, and done as fast as possible to encourage thorough soil mixing.

Crop rotation is usually not a component of an integrated weed management program for tobacco. Adequate land for rotation is often limited on farms. Heavy rains after transplanting may necessitate deep cultivation to "air" the soil, but as a general rule cultivation should be as shallow as possible to prevent bringing weed seed to the surface from below the chemically-treated zone. Cultivate only when crust or vegetation warrant.

Biological Controls: There are no biological agents for weed control in Kentucky tobacco production.

Post Harvest Control Practices: There are no post harvest chemical weed control practices. Many producers will plant cover crop grade wheat in the fall to help reduce soil erosion and to suppress out of season weed growth. In the spring this cover crop is tilled under and given sufficient time to decompose before setting tobacco plants.

Herbicide Controls: The primary herbicides used for Kentucky tobacco production are usually applied before plant setting. There are very few post-emergence herbicide applications made for tobacco. If chemical intervention is required, spray with properly calibrated ground equipment rather than impregnating herbicides on fertilizer. When using preplant incorporated materials do not incorporate deeper than 2 inches. Apply herbicides as close to transplanting as possible. Injuries to plants may occur if too an excessive amount of herbicide is applied, if applied unevenly, if incorporated to deeply or if cool, wet weather conditions retard tobacco growth.

In 1998, sethoxydim (POAST) was granted a 24c label for post-emergence control of a number of annual grass species. This label is currently good through 2005 in Kentucky. Sethoxydim is the only herbicide used in tobacco production that is used primarily as a post-emergence control measure.

Table 5. Pounds of Herbicide Active Ingredient Sold in Kentucky from 1992 – 2001. (KY Division of Pesticides)

Herbicide

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Benefin

1449

1537

562

1914

1994

3429

232

905

0

47

Clomazone

15559

11646

7328

8661

7181

17262

21538

19103

10229

9324

Sulfentrazone

0

0

0

0

0

2857

16044

10209

8376

9737

Napropamide

15480

19653

17136

14486

18718

16514

15137

13635

8908

5666

Sethoxydim

54

36

0

0

0

0

101

5043

817

887

Pendimethalin

151256

143357

115113

95243

136343

172608

100333

91115

76026

56833

Pebulate

101069

107125

74754

50318

48197

37951

30524

21957

13560

10352

Isopropalin

7385

1334

3900

2210

623

47

0

0

0

0

Diphenamid

196

14

38

0

0

0

0

0

0

0

Total

292449

284702

218831

172832

213056

250667

183908

161966

117916

92846

 

NOTE: Products listed under the chemical controls section for each weed species were rated as providing "Good" control in the Weed Control Recommendation for Kentucky Farm Crops 2003 (Extension publication AGR-6). It should be noted that product names and formulations are current as of 2003, however names and formulations may change in the future. It should also be noted that the species listed in this document is not an exhaustive list of weeds encountered in Kentucky tobacco fields. These species are some of the most commonly encountered.


Grass & Sedge Weed Species

Crabgrasses (Digitaria spp.)

  • Command (Clomazone)
  • Devrinol (Napropamide)
  • Prowl (Pendimethalin)
  • Tillam (Pebulate)
  • Spartan + Command (Sulfentrazone and Clomazone)

Fall panicum (Panicum dichotomiflorum)

  • Command (Clomazone)
  • Devrinol (Napropamide)
  • Prowl (Pendimethalin)
  • Tillam (Pebulate)
  • Spartan + Command (Sulfentrazone and Clomazone)

Foxtails (Setaria spp.)

  • Command (Clomazone)
  • Devrinol (Napropamide)
  • Prowl (Pendimethalin)
  • Tillam (Pebulate)
  • Spartan + Command (Sulfentrazone and Clomazone)

Shattercane (Sorghum bicolor)

  • No herbicides provided good control of this species.

Johnsongrass (seedling) (Sorghum halepence)

  • Prowl (Pendimethalin)

Johnsongrass (rhizome) (Sorghum halepence)

  • No herbicides provided good control of this species.

Yellow nutsedge (Cyperus esculentus)

  • Spartan (Sulfentrazone)
  • Tillam (Pebulate)
  • Spartan + Command (Sulfentrazone and Clomazone)

Broadleaf Weed Species

Black nightshade (Solanum ptycanthum)

  • Spartan (Sulfentrazone)
  • Spartan + Command (Sulfentrazone and Clomazone)

Cocklebur (Xanthium strumarium)

  • No herbicides provided good control of this species.

Hairy Galinsoga (Galinsoga quadriradiata)

  • Spartan + Command (Sulfentrazone and Clomazone)

Jimsonweed (Datura stramonium)

  • Spartan (Sulfentrazone)
  • Spartan + Command (Sulfentrazone and Clomazone)

Lambsquarters (Chenopodium album)

  • Command (Clomazone)
  • Prowl (Pendimethalin)
  • Spartan (Sulfentrazone)
  • Spartan + Command (Sulfentrazone and Clomazone)

Morningglories (Ipomoea spp.)

  • Spartan (Sulfentrazone)
  • Spartan + Command (Sulfentrazone and Clomazone)

Pigweeds (Amaranthus spp.)

  • Prowl (Pendimethalin)
  • Spartan (Clomazone)
  • Spartan + Command (Sulfentrazone and Clomazone)

Common ragweed (Ambrosia artemisiifolia)

  • Command (Clomazone)
  • Spartan + Command (Sulfentrazone and Clomazone)

Giant ragweed (Ambrosia trifida)

  • No herbicides provided good control of this species.

Smartweed (Polygonum pensylvanicum)

  • Spartan (Sulfentrazone)
  • Spartan + Command (Sulfentrazone and Clomazone)

Velvetleaf (Abutilon theophrasti)

  • Spartan + Command (Sulfentrazone and Clomazone)



Diseases

Table 2. Pounds of Fungicide Active Ingredient Sold in Kentucky from 1992 – 2001. (KY Division of Pesticides data)

Fungicide

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

Streptomycin

4401

634

142

408

433

674

508

372

191

169

Copper sulfate

1661

3517

226

1089

941

0

0

0

1931

0

Metalaxyl

97915

118853

79230

74532

52179

20716

1730

2672

480

384

Maneb

5

160

0

0

0

0

40

0

464

0

Mancozeb

20931

4710

486

43446

67583

53124

67000

15208

6967

5890

Ferbam

679

387

129

350

240

1634

2496

787

606

460

Dimethomorph

0

0

0

0

6668

4967

7728

1217

641

553

Mefenoxam

0

0

0

0

20502

49521

67522

39215

28781

41860

Tarrazole

0

0

0

0

0

0

0

25

67

687

Acibenzolar

0

0

0

0

0

0

0

0

0

377

Total

125592

128261

80212

119824

148546

130636

147023

59496

40127

50380


Overview

Stages in Plant Growth:

  • Seed Bed-
    Pre-Emergent (7 days)
    Seedling (40-60 days)
  • Field
    To Bud (60 days)
    To Flowering Top/ 1st Harvest (35 days)
    To Seed Formation/ 2nd Harvest (20 days)

Disease Parameters:

Diseases to tobacco cause major losses. Disease strikes at all stages of development and involves all plant parts. Two sorts of interactions with the tobacco host, those with pathogens and those with environmental factors, result in numerous costly diseases.

Among the pathogens of tobacco are bacteria, fungi, mycoplasmas, nematodes, parasitic plants and viruses. The resultant diseases are infectious (biotic diseases).

Environmental factors, including nutrient imbalances, adverse environment and air pollution, lead to non-infectious tobacco disorders (abiotic diseases).

Despite its resistance to most natural pathogens, tobacco remains susceptible to more than fifty organisms, which attack the plant and use its roots, stems or leaves as food. Some of these pathogens are plant-specific in attacking only tobacco; others have a range of potential hosts of up to 100 other plants. Using tobacco’s inherently disease resistant abilities, plant breeders have succeeded in developing yet stronger strains.

Diagnosis of disease, based on analysis of characteristic symptoms, must be approached with care since several pathogens produce identical or similar symptoms. A plant may also be attacked by several pathogens simultaneously.

Diseases are a limiting factor to tobacco production in Kentucky. Hence, they must be controlled if the farm is to remain profitable. Using the principle of disease prevention rather than that of rescue therapy best controls tobacco diseases. In other words, it is better to plan and implement agricultural strategies that will keep diseases to a minimum rather than waiting until the diseases develop to high levels and then finding that the tools in plant pathology are not routinely available to save crops from disaster.

Since there are many variables on each farm, it is difficult to arrive at a control "recipe" for all to use in the state; and, if we could, it would be unwise to approach disease control that way. Instead, growers should develop their own programs based on the following: know the disease threats to a particular community and farm, learn how diseases operate and incorporate management programs to minimize diseases. In general, look for approaches that take steps to reduce pathogen populations, improve the plant's resistance and avoid environmental conditions that favor disease development.

Because disease may strike tobacco at any stage, ranging from seedbed to field to barn, excellent sanitation and monitoring procedures must be established to protect the crop. Consultation with county extension offices as well as with the UK Disease Diagnostic Lab should be an important part of the overall plan.


Specific Diseases

Biotic Diseases (Infectious)

Bacteria- enter plants through wounds or natural openings. Phytopathogenic, they are single-celled, rod-shaped, prokaryotic organisms that seek chlorophyll and are present either locally or systemically. Soil, plant debris, seed, insects and infected plant tissue harbor the disease.

  • Foliar Diseases: Wildfire, Angular Leaf Spot, Hollow Stalk, Black Leg, Barn Rot, Philippine Bacterial Leaf Spot, and Leafy Gall (or Fascination)
  • Root Diseases: Bacterial Wilt

Fungi- develop from spores, which fall on plants and develop into tube-like filaments called hyphae. The hyphae grow between and through tobacco cells, secreting enzymes and sometimes toxins which break down host tissue. Fungi lack chlorophyll and must obtain their food from plant or animal organic matter. Several sport types are produced, easing their dissemination and survival.

  • Foliar Diseases: Blue Mold, Powdery Mildew, Brown Spot, Anthracnose, Frogeye, Target Spot, Gray Mold, Dead Blossom Leaf Spot, Ragged Spot, Phyllosticta, Leaf Spot, Corynespora Leaf Spot, Curvularia Leaf Spot, Scab, Metallic Mold, Sooty Mold, and Rusts
  • Root and Stem Diseases: Black Shank, Pythium Diseases, Black Root Rot, Stem Rot, Sore Shin, Damping-Off, Fusarium Wilt, Verticillium Wilt, Charcoal Rot, Tobacco Stunt, Olpidium Seedling Rot, and Collar Rot
  • Cured / Stored Tobacco Diseases: Barn Rot and Storage Molds

Mycoplasmas- are vectored by leafhoppers. Small- sometimes submicroscopic- organisms, they survive in their vector or in infected plant material.
Diseases: Aster Yellows, Stolbur and Big Bud

Nematodes- enter, live and feed in the roots where they use their stylets to extract cellular contents. They survive as eggs or larvae in soil.
Diseases: Root-Knot Nematodes, Tobacco Cyst Nematodes, Lesion Nematodes, Stem Nematodes and Ectoparasitic Nematodes

Parasitic Higher Plants- including dodder, broomrape and witchweed, attach to roots or stems and obtain nutrients from the plants.
Diseases: Broomrape, Witchweed and Dodder

Viruses- are generally vectored by aphids. The most important and severe virus, tobacco mosaic virus, is chiefly spread by mechanical transmission. Once the virus, a submicroscopic obligate parasite, enters the plant through a wound, it then replicates in cell after cell, moving systematically through the plant.

  • Diseases: Tobacco Mosaic Virus, Potato Virus, Tomato Spotted Wilt Virus, Cucumber
  • Mosaic Virus, Tobacco Etch Virus, Tobacco Vein Mottling Virus, Alfalfa Mosaic
  • Virus, Tobacco Leaf Curl Virus and Various Minor / Local Viruses


Abiotic Diseases (Noninfectious)

Nutritional Problems- Tobacco requires at least thirteen nutrients for normal growth. Given the variety of soil types and even differences within specific fields where tobacco is grown, attention needs to be given to assessing and amending depleted soils.

Proper fertilization and liming is necessary to prevent and correct nutritional disorders in order to provide for maximum economic production. Growers need to use a variety of available sources of information including soil nutrient and disease assays, cultivar identity, tissue analyses, fertilizer and liming rates, soil type, pH, growing conditions and cultural practices to assure that they will be operating with the most positive parameters.

Nitrogen, potassium, phosphorus, magnesium, calcium, boron, manganese, sulfur, copper, iron and zinc are among the most critical substances.

Toxicities- While the absence of correct nutrients can undermine normal growth in tobacco, excessive amounts of nitrogen, chlorine, boron, copper, iron, and manganese can also cause injury to plants. Monitoring fields to avoid over-fertilizing, while maintaining proper pH and adequate moisture are quite important.

Environmental Disorders- Several environmentally sourced stresses pose a lethal threat to tobacco. Seedlings can be injured by frost or cold. Drought, sunscald, lightning, hail and flooding can also injure or kill crops. An understanding of the local climate, as well as of assorted physical impacts on various fields can permit the making of decisions which may minimize damage.

Genetic Abnormalities- may be confused with other diseases. They are infrequent, but not rare.


Integrated Pest Management

Controls

Biological

Little success has been achieved in developing biological controls yet. It is an area being researched energetically.

Cultural

Cultural controls make up the major efforts tobacco growers use for pest control. Clean cultivation approaches are applied from seed bed to field in order to avoid or minimize contamination by disease and to provide a healthy environment for the growing crop. The use of disease-resistant plants is an important part of the process. No-till practices have been used on an increasing number of acres as growers with steep land try to bring their Class III acreage into production in order to increase their incomes.This land is prone to erosion and probably should not be planted in any row crops.

Traditionally, cultivation practices for weed control have also been useful for disease control because reduction or elimination of some plant vectors as well as maintenance of needed soil moisture contribute to healthy plant development.

Chemical

Special Issues for Kentucky:

The EPA (June 1998) restated its position regarding pesticide use in the greenhouse: Labels must specifically cite the greenhouse and greenhouse-crop-stage as a site if the product is to be used in greenhouse production systems. The Atlanta Regional Office continues to advise that if the product is intended for use in float-beds, within greenhouses or outside, then specific instructions must also be included on the label to either avoid contamination of the float-water or address proper disposal of the treated water. Thus, the float-bed is perceived as a different site from the traditional ground bed, and different precautions must be taken.

As of spring 1999, the only fungicides labeled for any tobacco transplant production in Kentucky are Ferbam and Dithane DF, which are covered by special state labels (24-c). Streptomycin, an antibiotic, is labeled only for tobacco beds (traditional ground beds). It is not labeled for greenhouse use nor for float-beds.

Seedbed Stage

Greenhouse and / or Float-Beds
Anthracnose, Blue Mold and Damping-Off due to Rhizoctonia and Fusarium

  • Monitoring:
    • -Watch the development of seedlings carefully.
    • -Compare suspicious signs to diagnostic photos.
    • -Send samples to UK Disease Diagnostic Lab

  • Application:
    • Dithane DF: (21 day PHI) (24 hr REI) Application at 0.5 lbs./100 gallons of water (one-two teaspoons / gallon). Spray preventatively on a 5-7 day schedule starting when plants are about the size of a dime and continuing until transplanting to the field. [Note: The rate is lower for greenhouse and float-beds than in the outdoor soil-plant beds.] Use 3 gallons of spray per 1000 sq. ft. while plants are small, but increase gradually to 6-12 gallons as plant size and canopy increase. Be sure sufficient water is used to wet the base of the stems with run-off to increase the potential control of damping-off. Avoid contamination of the float-water during applications. This use is labeled under a (24-c) in Kentucky which expired June 16, 1999.
    • Ferbam Granuflo: (24 hr REI) Application at 1.5-3.0 lbs. /100 gallons of water (one-two teaspoons / gallon). Spray preventively twice weekly starting when seedlings have the first true leaf or immediately after plugging with the plug-and-transfer system. Apply as a fine spray to the point of run-off, using 3 gallons of spray material per 1000 sq. ft. when seedlings are small and increasing gradually to 6-12 gallons as plants increase in size and canopy increases. The label has a specific restriction to avoid contamination of the float-water. This use is labeled under a (24-c) in Kentucky, which expired June 16, 1999.
  • Special Note: In Kentucky tests, Dithane DF has caused damage to seedlings under certain conditions (especially if the float-water becomes contaminated), but it clearly has provided superior control of blue mold in the outdoor float-beds compared to Ferbam. In greenhouse plantings, significant differences have not been observed in the control of blue mold offered by Ferbam and Dithane DF. Ferbam was superior to Dithane DF in Botrytis Control at the labeled concentrations.


Tobacco Mosaic Virus

  • Monitoring:
    • Watch the development of seedlings carefully.
    • Compare suspicious signs to diagnostic photos.
    • Send samples to UK Disease Diagnostic Lab
  • Application:
    • Milk: Application of whole or skim milk at 5 gals. / 100 gallons of water or dried milk at milk at 5 lbs. / 100 gallons of water per 100 sq. yds. of plants. Spray plants 1-24 hours before handling them. This treatment has also been used successfully prior to clipping of large plants, but it can be very messy unless the system dries well following the application. It should be combined with washing the hands in clean milk solution or in a phosphate detergent. This treatment is warranted if TMV susceptible varieties are being used or if in mixed houses with resistant and susceptible varieties.


Traditional-Type, Outdoor Soil-Plant-Beds

Soil-Borne Pathogens

  • Monitoring:
    • Watch the development of seedlings carefully.
    • Compare suspicious signs to diagnostic photos.
    • Send samples to UK Disease Diagnostic Lab
  • Application:
    • Gases: (including products containing methyl bromide or methyl bromide + Chloropicrin). Application should be carried out under a plastic tarp. Methyl bromide should be applied at the rates of 9-18 lbs. / 1000 sq. ft. of bed. (Check labels for specific rates on each product.) Methyl bromide and Chloropicrinshould be applied at 9-13 lbs. / 1000 dw. Ft. of bed depending on the product used. Bed sites should be prepared as if ready to seed then fumigated for best results. Expose the site to fumigant for at least 24 hrs. Soil temperatures should be above 55F during the fumigation period and soil moisture should be sufficient to support germination. Gas fumigants are extremely poisonous, so follow safety precaution statements fully.
    • Liquid Fumigants: (including products containing SMDC Ametham sodium@ and marketed under such names as Vapam and Sectagon. Other products may be available in some areas.) Application should be made at the rate of 1.5 gals. / 1000 sq. ft. of bed, injected into the soil to a depth of at least 4 in. or more, or drenched into the soil with at least 40 gallons of water / 1000 sq. ft. of bed area and then covered immediately with plastic tarp. The tarp should be left in place at least 24-48 hrs., but a long aeration period of 21 days is needed prior to seeding. Light tillage of the soil during the aeration period may be helpful to speed escape of the fumigant. Be sure that tillage equipment is very clean to avoid re-contamination of the soil.
    • Granule fumigants: (available as Dazomet, sold as Basamid: Application should be made at 7.5 lbs. / 1000 sq. ft. of bed. Since it has a very long aeration requirement (14-50 days), its use in the spring in Kentucky is greatly limited. Granules should be spread evenly over the bed site and incorporated to a depth of 8 in. Then the site must be sealed completely with plastic which should stay in place at least 5-7 days. Aerate the site until it is safe to seed, as determined by a germination test.
  • Field Stage


Angular Leaf Spot
Pseudomonas syringae pv. tabaci

Angular Leaf Spot is a bacterial disease with symptoms typical of other leaf-spot diseases. Its spots are at first water-soaked; they later become necrotic, burn brown or black upon drying and have angular margins. The disease often develops in "hot spots," spreading out from localized areas of initial infection. It tends to develop during periods of heavy, windblown rains. Severely infected leaves become ragged and are of little value.

Spread of the bacteria occurs when there is movement of water from a source of the bacteria to tobacco plants. This occurs when surface water washes bacteria from infested to non-infested areas, or when rainfall or overhead irrigation water splashes the bacteria from the soil onto tobacco leaves in the seedbed or field. Spread from leaf to leaf or plant to plant occurs primarily during wind-driven rainfall but also occurs during pulling and handling of wet plants.

Water soaking of leaf tissues greatly facilitates the movement of bacteria into the leaves and their subsequent development. A number of factors favor water soaking and thus increase disease severity. Chief among these are rainstorms accompanied by high winds, during which water is physically driven into the intercellular spaces of the leaves. However, the diseases also occur during periods of high humidity, high soil moisture and gentle rains (or frequent irrigation) and are favored by high nitrogen and low potassium fertilization. Once inside water-soaked leaves, bacteria multiply rapidly, ooze out of necrotic tissue when wet and are spread during splashing rain and irrigation.

It is preferable to control angular leaf spot in the seedbed.

Controls

Biological

  • None available.

Cultural

  • Use resistant varieties.
  • Exercise excellent sanitation.

Chemical

  • Monitoring:
    • Watch the development of seedlings carefully.
    • Compare suspicious signs to diagnostic photos
    • Send samples to UK Disease Diagnostic Lab
  • Application:
    • Streptomycin: Streptomycin has an REI of 12 hours. Applied by ground spray; plants must be sprayed until run off. A late day application is preferable. Application rate .5-1 lb. per 100 gallons of water. 


Blue Mold
Peronospora tabacina

Blue mold is a particularly aggressive plant pathogen which flourishes when the weather has been unseasonably cool and wet. The blue mold pathogen usually infects only plants in the genus Nicotiana. Cultivated tobacco is highly susceptible. P. tabacina leads to extensive destruction of tobacco leaf tissue, systemic infection and stunting of plants. Blue mold tends to be epidemic and difficult to control because its causal agent is spread over long distances rapidly and efficiently by windblown sporangiospores. Humidity supports the process.

The symptoms of blue mold vary with plant age. Young plants less than a month old are very susceptible and may be killed outright. Blue mold may affect plants in the field throughout the growing season. Groups of yellow spots usually appear on the older, shaded leaves. Often the spots coalesce to form light brown, necrotic areas. Leaves become puckered and distorted, large portions disintegrate and the entire leaf may become unusable. Under continued favorable weather conditions, the fungus can destroy all leaves at any growth stage. Blue mold may also damage tobacco in the curing barn.

Controls

Biological

  • None available.

Cultural
  • Prior to planting employ a soil-incorporation treatment of metalaxyl.
  • Plant resistant cultivars.
  • Locate seedbeds where they receive a maximum amount of sunshine.
  • Avoid damp, shaded, poorly drained sites.
  • Avoid using tobacco trash as fertilizer on seedbeds.
  • Disk under remaining plants from transplanting and harvest and plant a cover crop.
  • Attend to agriculture weather reports diligently.

Chemical

  • Monitoring: (Spraying should begin before blue mold starts in the field.)
    • -Watch the development of seedlings carefully.
    • Compare suspicious signs to diagnostic photos
    • Send samples to UK Disease Diagnostic Lab
  • Application:
    • Dimethomorph (Acrobat MZ): Acrobat MZ has an REI of 24 hr and a PHI of 30 days. Application rate of 2.5 lbs per 100 gallons of water.
    • Mancozeb (Dithane DF): Dithane DF has a REI of 24 hr and a PHI of 21 days. Applied when by ground or aerial spray or chemigation. Application rate of 1.5-2 lbs. per 100 gallons of water. Repeat applications weekly except during wet periods when twice weekly applications are needed.
    • Metalaxyl (Ridomil 2E): Ridomil 2E has a REI of 48 hr. Applied preplant by broadcasting and incorporating 2-4 inches. Application rate of 2 qts. per acre.


Black Shank
Phytophthora nicotianae

Black shank is a destructive root and stem rot disease of all types of cultivated tobacco. The fungus primarily affects the roots and basal stem region of the tobacco plant, but all parts of the plant can be infected. Black shank is most severe in warmer climates and tobacco appears to be the only natural host for the fungus.

Symptoms vary with plant age and weather conditions. During periods of rainy weather, the fungus may infect lower leaves of tobacco as infested soil is splashed onto the leaves. The fungus often grows into the stem from leaf infections and causes typical black shank symptoms. High soil moisture conditions also enhance disease. Soil factors other than temperature and moisture affect pathogen activity and development of black shank. These include parent material, soil series and soil texture. Black shank is generally less severe in poorly drained soils, probably because such soils are usually more acid than well-drained soils, and soils that are periodically flooded provide conditions that are not optimum for fungus survival.

In the field, the first aboveground symptom is wilting of the leaves during the middle of the day. Plants usually recover overnight, only to wilt more severely the next day. In general all of the leaves wilt. Depending on the level of soil moisture and level of host resistance, leaves begin to turn yellow and hang down the stalk over the next few days to weeks. In the final stages the stem, or shank, turns black 30 cm. or more aboveground. At this point, leaves turn brown, shrivel and are not marketable.

The pathogen is spread on infected transplants, in water or in soil. Infected transplants may not show any symptoms, but under favorable conditions the disease continues to develop after transplanting. Rainwater transports infested soil and fungus spores along rows; from infested areas of a field into uninfested areas of the field; and into drainage ponds, creeks and rivers. Subsequent irrigation from infested water may result in introduction of the fungus to uninfested areas. Soil adhering to farm equipment and even the shoes of workers also harbors the fungus. The fungus is present in stalks of infected plants, so these stalks should not be placed on seedbed sites or noninfested fields. The severity of black shank is greatly increased in the presence of root-knot nematodes.


Controls

Biological

  • None available.

Cultural

  • Use resistant cultivars.
  • Rotate crops.
  • Control nematodes.
  • Exercise excellent sanitation.

Chemical

  • Monitoring:
    • Watch the development of seedlings carefully.
    • Compare suspicious signs to diagnostic photos
    • Send samples to UK Disease Diagnostic Lab
  • Application:
    • Metalaxyl (Ridomil 2E): Ridomil 2E has a REI of 48 hr. Applied preplant by broadcasting as close to transplanting as possible. Application rate of 2-6 qts. per acre.
    • Metalaxyl (Ridomil Gold EC): Ridomil Gold has an REI of 48 hrs. Applied to soil by ground spray or chemigation. Application rate is 1 pt. per acre.


Hollow Stalk
Erwinia carotovora

Hollow stalk is sporadic in appearance and seldom causes much loss. It usually appears first at topping and suckering time. Top leaves wilt, and as the infection spreads downward, leaves droop and hang down or falloff, leaving the stalk bare. Stem lesions develop as black stripes or bands that eventually girdle the stalks. Bacteria occur in great numbers in the lesions and are easily isolated from infected plants.

. Infested soil rubbed onto hands to alleviate the sticky feeling of leaf gum results in hand transfer of the bacteria during topping and suckering. Any wound made during topping and suckering of the plants or harvesting the leaves provides invasion loci for the bacteria. Once in contact with parenchymatous cells, rapid multiplication occurs. Rotting may be evident within 48 hr. after inoculation, and the diseased tissue may extend the entire length of the mature stalks within a few days to a week. During periods of humid weather, leaves harvested from infected plants or inoculated by bacteria carried on the harvester's hands sometimes continue to rot in the curing barn.

Controls

Biological

  • None available.

Cultural

  • Avoid topping and suckering during damp or cloudy weather, as these conditions are ideal for the spread of the pathogen.

Chemical

  • None available.

Sore Shin
Rhizoctonia solani Kuhn

All types of tobacco are susceptible to sore shin, yet losses tend to be insignificant. Injury to plants in the field tends to be less than to those in seedbeds. The fungus is a soil inhabitant and has a wide host range.

The first symptom of sore shin is a small water-soaked area on the stem near the soil line. This area rapidly becomes dark brown and sunken. The lesion may remain small or continue to enlarge until the stem is girdled. If infected seedlings are transplanted, the disease continues to develop into a canker that often enlarges and extends up to the lower leaves. This symptom may be confused with black shank.


Controls

Biological

  • None available.

Cultural

  • Prevent injuries to the transplants to reduce infections, particularly be careful not to bruise stem or to cause fertilizer injury.

Chemical
  • None available.



Contacts

Bill Nesmith
Plant Pathology Department, S-305 ASCN
University of Kentucky, Lexington, KY 40546-00917
(859)-257-3991

Lee Townsend
Entomology Department
S-225 Ag Science North
University of Kentucky
Lexington, KY 40546-0091
(859)-257-7455
ltownsen@uky.edu

Lowell Sandell
Entomology Department
S-225 Ag Science North
University of Kentucky
Lexington, KY 40546-0091
(859)-257-6693
lsandell@uky.edu



Resources

  • Crop Protection Reference, 1998

  • Compendium of Tobacco Diseases. The American Phytopathological Society Press, North Carolina State University.

  • Kentucky Pest News: 1998-1999. Cooperative Extension Services, University of Kentucky.

  • Tobacco in Kentucky (ID-73), 1993. Cooperative Extension Services, University of Kentucky.

  • Gross, B., D Mundy, V. Witcher, and P. Kenkel. 2001. Budgeting in burley tobacco. U.Tennessee Coop Extension Pub AE&RD 70. 7 pp.