Tobacco Scourge

DISEASES AND OTHER DAMAGE TO TOBACCO

Tobacco diseases cause damage, from seed stage to production, and insects and bugs, from seedling to post-production.

There are seven categories tobacco disease: 1. Foliar Diseases Caused by Fungi, 2. Root and Stem Diseases Caused by Fungi, 3. Diseases of Cured and Stored Tobacco, 4. Root Diseases Caused by Bacteria, 5. Diseases Caused by Nematodes, 6. Diseases Caused by Viruses, and 7. Diseases Caused by Parasitic Higher Plants. The eighth category includes moths, larva, ants, and other invading enemies.

BABILLA; STIFLE: This disease affects the middle bunches of seedlings, pulled for transplanting, when there has been a great deal of moisture from dew, rain, or improper irrigation. The spittle-like substance at the base of the roots prevents the seedlings from taking root. The term origins is in the plain meaning, i.e., to choke off, smother, or suffocate, which the rot does to the seedling roots.

BIBIJAGUA: These are giant ants, also known as leaf-cutting ants. Cuba has the distinction of being the only country inhabited by bibijagua (Atta insularis Güerin). Bibijagua were classified in l845. They are generally black, and only the young have a brown coloration. The ants subsist entirely on a particular species of fungus which it cultivates on a medium of masticated leaf tissue. This is the sole food of the queen and other colony members that remain in the nest. The workers also gain subsistence from plant sap they ingest while physically cutting out sections of leaf from the plant.

BLACK SHANK: This disease primarily affects the roots and basal stem region of the tobacco plant. Black shank gets its name from the typical black appearance on the shank of the plant. When the stem of a diseased plant is split into the vascular region appears dry and darkened and usually forms discs or plates within the center of the shank.

The black shank fungus can infect tobacco plants of any age. In young seedlings, stems may decay near the soil surface and the root system may become partly or completely black. A dark lesion may extend up the stem. Leaves may suddenly and uniformly wilt or droop, turn yellow, and hang down the stalk. Warm, moist weather conditions favor black shank development. Advanced stages of this disease may cause partial or complete decay of the root system. The black shank fungus is soil-borne and is readily trans-located by equipment or water movement to non-infested areas.

Black shank infection may occur on lower leaves of a plant due to spores being splashed onto them by hard rains. Large lesions, up to 3 inches, with a greenish-brown to yellow color are formed on the infected leaves. The disease is characterized by a rapid yellowing and wilting followed by death of the entire plant. A dark brown to black, somewhat sunken, lesion usually appears on the stalk at or near the ground level. This lesion often extends up the stalk or shank of the plant causing it to turn black.

Black shank is caused by the fungus Phytophthora parasitica var. nicotiana which lives in the soil. This pathogen belongs to a group of fungi that occurs commonly in areas of high soil moisture. The fungus produces microscopic spores which swim in water surrounding roots and/or soil particles. These swimming spores are attracted to tobacco, their only natural host, by root exudates produced primarily at growing points and wounds. Whereas wounds are not required for penetration, they do favor more rapid disease build-up.

The black shank fungus is spread when infested soil is moved from one place to another. Contaminated irrigation or runoff water may also aid in its movement within a field or from one field to another.

BLUE MOLD:

(Peronospora tabasina): This is also known as DOWNY MILDEW. This feared fungus, arising from adverse temperature and moisture conditions, can destroy an entire tobacco field in days. It is characterized by the appearance of brown necrotic spots on the leaves which, soon, develop a bluish-grey coating. Eventually the leaves dry out and droop.

BROOMRAPE; (Orobanche ramosa L.): Plants attacked by broomrape appear sickly, yellowish, and starved, but have few distinguishing symptoms. The presence of small white, yellow, or purple plants with blue flowers growing near the base of the affected tobacco plant is the most diagnostic feature of broomrape. The parasitic plants' roots are attached to the tobacco plant. Stunting symptoms occur because the broomrape plant is taking much of the tobacco plant's food. Affected plants may be located singly or clustered.

Broomrapes are obligate root parasites, and their seeds germinate only in response to specific chemical signal(s) elicited of the host plant, tobacco.

The pest lacks chlorophyll, and takes all its nourishment from the host plant. It is spread by tiny (less than 0.5 mm) seeds which are easily carried by farm and construction equipment, water, wind, or animal droppings. Germination takes place in December through February. Each seed puts out a root-like growth which attaches to the roots of nearby hosts. Once attached to a host, it robs its host of water and nutrients. The above ground stems first start to appear in February with the majority appearing in March and April. The first flowers appear just three days after the plant breaks ground, and seed pods mature in just 14 days. Each plant may produce 50,000 or more seeds.

The broomrape plant is small, only 4 to 12 inches tall. The pest is best recognized by its yellow to straw color stems and blue or white, snapdragon like flowers. The plant generally flowers from February through May.

CANDELILLA: This refers to the tobacco leaf borer, known as Furro de Catre, and the Tobacco Splitworm; it eats the main veins of the leaf.

CHINCHITA DE LA HOJA DEL TOBACCO: These are small bugs found on most tobacco leaves, and are relatively harmless.

CUTWORM: This is the name for the larvae of many moths of the family Noctuidae (owlet moths). The larvae, or caterpillars, feed at night on the stems and roots of young plants, often cutting them off near the surface of the ground. They hide in soil by day. An average cutworm consumes 65 sq. in. of foliage during its development. Most species pupate underground. Many species, over winter in the pupal stage, emerge as adults in the spring and laying eggs from which the larvae hatch in summer.

Cutworm caterpillars have three pairs of legs near their heads and five pairs of prolegs. Several species of these thick-bodied, grayish to dark brown larvae, up to 50 mm in length, hide curled up in the soil by day, and feed at night on seedlings or newly set plants in the field. They sever the stems of young plants, cut off leaves, or chew large holes in the leaves.

GRILLITO DE LA TIERRA: This is a big name for a small cricket which eats the tobacco leaf.

PINTA DE AJONJOLI: This is a natural enemy, which may occur when the weather is hot and humid. It is a fungal disease manifested by iron spots, which discolor the upper leaves of the plant. While the damage is minimal, it reduces the wrapper crop. It is a pathogen, causing rough, circular spots on the leaf. It is commonly referred to as Frog-Eye Leaf Spot.

PINTA DE HEIRRO: This term literally means ‘iron dot’. It is observed as the reddish color of oxide of iron which is seen as a spot in the leaf, mainly in the leaves of the crown and semi-corona. It is not harmful, and affects tobacco in dry seasons.

PUDRICJON: This is a class of fungus rot caused by the Rhizoctonia specifica, and attacks young plants, or seedlings, shortly after transplanting, in hot and humid conditions. It is also referred to as Pudricion Negra. It appears, first, as large, wet, green spots on the bottom and lower middle leaves.

PUDRICION DEL TALLO: This is the Cuban name for Stem Rot or Black Shank. This disease has not appeared in Cuban crops for many years. This stem rot is identified by yellowish spots on the lower part of the stem, mainly in the section containing the bottom and lower middle leaves. This spot turns grayish or dark in color and increases in size as it wilts the leaves and turns them yellow, occurring before the disease entirely circles the stem, causing the plant to die. This form of rot is no longer prevalent in Cuba, but can appear during rainy years on low-lands.

SAHORNE: This is a rot which forms on damp leaves during the curing process, when the temperature is at a constant high for a short period.

SAND DOWN: This is a nonparasitic disease called Frenching. It is considered to be a nonparasitic disease because the organism or organisms that cause the disease do not live within the tissues of the plant. Early symptoms of frenching consist of chlorosis (yellowing or whitening of normally green plant tissue because of a decreased amount of chlorophyll), along the margins of young leaves. The chlorosis gradually spreads toward the midrib until all interveinal regions are involved. The veins remain dark green. As the leaf continues to develop, only the midrib elongates which produces a long, ribbon-like leaf. It is also referred to as Interveinal Chlorsis, and is generally found on younger leaves.

TOBACO SENTIDO: One of the many names for the type of tobacco rot which occurs when tobacco, stored in bulk, is too wet or the ambient temperature is too high. It can occur if the dampening process is not properly done; it is also called Improper Petuning.

WHITE MOLD: A light grey thread-like fungus that appears on leaves that have been rained upon after the tobacco has been fully dried and the laths separated in the curing barn. This will cause the tobacco to rot if care is not taken.

TOBACCO BUDWORM: Eggs are deposited on blossoms, fruit, and terminal growth. The eggs are spherical, with a flattened base. Eggs initially are whitish to yellowish white in color, but turn gray as they age.

Pupation occurs in the soil, are shiny, reddish-brown in color, becoming dark brown prior to emergence of the adult.

Larvae bore into buds and blossoms (the basis for the common name of this insect), and sometimes the tender terminal foliar growth, leaf petioles, and stalks. In the absence of reproductive tissue, larvae feed readily on foliar tissue.

TOBACCO MOSAIC VIRUS - TMV: Severely affected plants are stunted by the virus, and yields may be reduced by as much as 25%.

The leaves become light, and then dark green, or yellowish-green mottling, with puckered areas. Narrowed leaflets result in a fern-like appearance on new growth. The stems become dark brown, and these color streaks may develop on the stems and petioles.

The virus is transmitted by mechanical means from affected crops or weed hosts. Hands and clothing can become contaminated while handling affected plants or tobacco products. The virus is easily transmitted by smokers and tobacco product users by touching plants and equipment with tobacco contaminated hands and clothing. The virus is easily spread when infected and healthy plants are handled together.

TMV is well noted for being highly infectious. For example, the virus has been shown to persist in root debris at a depth of 120 cm for at least two years. It was one of the first tobacco viruses to be identified.

THE COMPLETE LIST OF INFECTIOUS DISEASES OF TOBACCO

Foliar Diseases Caused by Fungi; Blue Mold, Powdery Mildew, Brown Spot, Anthracnose, Frogeye, Target Spot, Gray Mold and Dead-Blossom Leaf Spot, Ragged Leaf Spot, Phyllosticta Leaf Spot, Corynespora Leaf Spot, Curvularia Leaf Spot, Scab, Metallic Mold, Sooty Mold, Rusts; Root and Stem Diseases Caused by Fungi; Black Shank, Pythium Diseases, Black Root Rot, Stem Rot, Sore Shin and Damping-Off, Fusarium Wilt, Verticillium Wilt, Charcoal Rot, Tobacco Stunt, Olpidium Seedling Blight, Collar Rot; Diseases of Cured and Stored Tobacco; Barn Rots, Storage Molds; Foliar Diseases Caused by Bacteria; Wildfire and Angular Leaf Spot, Hollow Stalk, Black Leg, and Barn Rot, Philippine Bacterial Leaf Spot, Leaf Gall or Fasciation; Root Diseases Caused by Bacteria; Bacterial Wilt; Diseases Caused by Mycoplasma-like Organisms; Aster Yellows, Stolbur, and Big Bud; Diseases Caused by Nematodes; Root-Knot Nematodes, Tobacco Cyst Nematodes, Lesion Nematodes, Stem Nematodes, Ectoparasitic Nematodes; Diseases Caused by Viruses; Tobacco Mosaic Virus, Potato Virus Y, Tomato Spotted Wilt Virus, Cucumber Mosaic Virus, Tobacco Etch Virus, Tobacco Vein Mottling Virus, Alfalfa Mosaic Virus, Tobacco Leaf Curl Virus; Diseases Caused by Parasitic Higher Plants; Broomrape, Witch weed, Dodder.

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