- Tomato mosaic virus and tobacco mosaic virus
- Quick Facts
- Host and pathogen
- Signs and symptoms
- Biology and disease cycle
- Cucumber Mosaic Virus
- Disease Cycle
- Crops affected by this disease include:
- How to Manage Pests
- UC Pest Management Guidelines
- Viruses of cucurbits
- What causes viruses
- The Plant Doctor – Tobacco Mosaic Virus
- Cucumber Mosaic Virus Symptoms And Treatment
- What Causes Cucumber Mosaic Disease?
- Cucumber Mosaic Virus Symptoms
- Cucumber Mosaic Virus Treatment
Tomato mosaic virus and tobacco mosaic virus
- Tomato mosaic virus (ToMV) and Tobacco mosaic virus (TMV) are hard to distinguish.
- Tomato mosaic virus (ToMV) can cause yellowing and stunting of tomato plants resulting in loss of stand and reduced yield.
- ToMV may cause uneven ripening of fruit, further reducing yield.
- Tobacco mosaic virus (TMV) was once thought to be more common on tomato.
- TMV is usually more of a tobacco pathogen than a tomato pathogen.
Host and pathogen
ToMV infects tomato most commonly, but the virus can also infect pepper, potato, apple, pear, cherry and numerous weeds, including pigweed and lamb’s quarters.
Symptoms may differ on different hosts. TMV has a very wide host range, affecting numerous crops, ornamentals and weeds including cucumber, lettuce, beet, pepper, tomato, petunia, jimson weed and horsenettle.
Signs and symptoms
Green and yellow mosaic pattern on leaf infected with TMV
Overall, tomato mosaic virus symptoms can be varied and hard to distinguish from other common tomato viruses. A definitive diagnosis can be accomplished by submitting a sample to the University of Minnesota Plant Disease Clinic.
- Mottled light and dark green on leaves. Tobacco Mosaic virus symptoms on a tomato seedling
- If plants are infected early, they may appear yellow and stunted overall.
- Leaves may be curled, malformed, or reduced in size.
- Spots of dead leaf tissue may become apparent with certain cultivars at warm temperatures.
- Fruits may ripen unevenly.
- Reduced fruit number and size.
- Yellowish rings may form if fruit ripens in warm weather.
- Fruits may show internal browning just under the skin (brownwall).
- Symptoms may be suppressed during cool temperatures. As a result, infected seedlings may not display symptoms until moved to a warm environment.
Biology and disease cycle
Tomato mosaic virus and tobacco mosaic virus can exist for two years in dry soil or leaf debris, but will only persist one month if soil is moist. The viruses can also survive in infected root debris in the soil for up to two years.
Seed can be infected and pass the virus to the plant but the disease is usually introduced and spread primarily through human activity. The virus can easily spread between plants on workers’ hands, tools, and clothes with normal activities such as plant tying, removing of suckers, and harvest.
The virus can even survive the tobacco curing process, and can spread from cigarettes and other tobacco products to plant material handled by workers after a cigarette. Proper hand washing and sterilization of tools and equipment is essential to preventing spread this disease.
Once inside a plant, the virus multiplies resulting in the symptoms described above.
There are numerous tomato varieties that are resistant to one or the other of the viruses. These are usually denoted in seed catalogs, often with the code ToMV after the variety name if resistant to tomato mosaic virus and TMV if resistant to tobacco mosaic virus. There are only a few varieties that are resistant to both viruses.
Several popular rootstocks for grafted tomatoes can also confer resistance to varieties that may not normally be resistant.
Tomato varieties resistant to ToMV and TMV
|ToMV Resistant||TMV Resistant||Resistant to both||Resistant Rootstock|
|Bolseno||Big Beef||BHN-444||Estamino (ToMV)|
|Tomimaru Muchoo||Celebrity||Health Kick||DRO138TX (ToMV)|
|Pink Wonder||BHN-871||Sophya||Colossus (TMV)|
A more extensive list of resistant tomato varieties can be found at Cornell University’s Vegetable MD Online.
- Use certified disease-free seed or treat your own seed.
- Soak seeds in a 10% solution of trisodium phosphate (Na3PO4) for at least 15 minutes.
- Or heat dry seeds to 158 °F and hold them at that temperature for two to four days.
- Purchase transplants only from reputable sources. Ask about the sanitation procedures they use to prevent disease.
- Inspect transplants prior to purchase. Choose only transplants showing no clear symptoms.
- Avoid planting in fields where tomato root debris is present, as the virus can survive long-term in roots.
- Wash hands with soap and water before and during the handling of plants to reduce potential spread between plants.
- Disinfect tools regularly — ideally between each plant, as plants can be infected before showing obvious symptoms.
- Soaking tools for 1 minute in a 1:9 dilution of germicidal bleach is highly effective.
- Or a 1-minute soak in a 20% weight/volume solution of nonfat dry milk and water is also very effective.
- When pruning plants, have two pruners and alternate between them to allow proper soaking time between plants.
- Avoid using tobacco products around tomato plants, and wash hands after using tobacco products and before working with the plants.
- Tobacco in cigarettes and other tobacco products may be infected with either ToMV or TMV, both of which could spread to the tomato plants.
- Scout plants regularly. If plants displaying symptoms of ToMV or TMV are found, remove the entire plant (including roots), bag the plant, and send it to the University of Minnesota Plant Diagnostic Clinic for diagnosis.
- If ToMV or TMV is confirmed, employ stringent sanitation procedures to reduce spread to other plants, fields, tunnels and greenhouses.
- Completely pull up and burn infected plants. Do not compost infected plant material.
- After working with diseased plants, thoroughly disinfect all tools and hands as outlined above.
- For added security against spread, keep separate tools for working in the diseased area and avoid working with healthy plants after working in an area with diseased plants.
- At the end of the season, burn all plants from diseased areas, even healthy-appearing ones, or bury them away from vegetable production areas.
- Disinfect stakes, ties, wires or any other equipment between growing seasons using the methods noted above.
There are currently no chemical options that are effective against either virus.
Anna Johnson; Michelle Grabowski, Extension educator and Angela Orshinsky, Extension plant pathologist
Reviewed in 2015
Cucumber Mosaic Virus
Cucumber Mosaic Virus (CMV) can cause severe losses in vegetables, legumes, and ornamentals. The virus is distributed worldwide but is particularly prevalent in temperate regions. It has a host range of more than 1,200 species, and is transmitted by many species of aphids, as well as cucumber beetles. Vegetable hosts include carrot, celery, cucurbits, legumes, lettuce, onion, pepper, spinach, tomato, and rarely potato. Many woody and non-woody ornamentals are also hosts.
Symptoms of CMV vary with viral strain, crop host and genotype, crop maturity stage, and environmental conditions.
The most easily identified symptom of CMV in celery is a downward curling of young petioles, which gives plants and opened or flattened look. Leaves may develop vein-clearing and mosaic, and interveinal areas may become dark green and thick, making leaves look crinkled. Symptoms are often transient, becoming more and less obvious as the season and weather progress. Plants that are infected with CMV when they are young may develop elongated brown to translucent sunken spots on their petioles.
Symptoms of CMV in cucurbits generally manifest as severe stunting, prominent yellow foliar mosaic, plant and leaf malformation, and stunting due to drastic reduction of leaf size and stem internodes. When the virus becomes systemic, leaves prominently curl downward, develop a mosaic pattern, and remain small. Flowers develop abnormalities and have greenish petals. Foliar and flower symptom intensity varies with species and cultivar: symptoms are most severe in summer squash, some pumpkins, and many melons and less severe in cucumber, winter squash, and watermelon. Infected fruit are often distorted and discolored, remain small, and, when severely infected, produce a negligible amount of seeds.
Peppers infected with CMV develop mosaic and necrotic symptoms. In greenhouse peppers, short-lived vein-clearing patterns may develop. In field and greenhouse peppers, mosaic symptoms will fade over time and leaves will become dull green, brittle, and leathery. Systemically infected leaves become narrow and remain small, and plants appear stunted due to shortened internodes. Infected plants will often produce the same number of fruit as uninfected plants, but fruit will be small and fewer will be marketable quality. Fruit has a wrinkled, bumpy appearance, pale to yellowish green color, and often ripens irregularly. Sometimes, fruit will develop sunken lesions with necrotic centers. In some varieties, necrotic lines or ringspots will develop. As in tomato, symptom severity is influenced by the maturity of the plant at the time of infection. Young plants are more likely to develop symptoms as described above, whereas older plants have more resistance to CMV and show few foliar or fruit symptoms.
The most characteristic symptom of CMV in tomato is filiformity, or the development of thin, shoestring-like leaves. In early stages of infection, foliage will also turn yellow and plants will become bushy and stunted with mottled leaves. Foliar symptoms can be transitory, meaning that the bottom- and top-most leaves will be affected but middle leaves will remain symptomless. Severely affected plants often do not produce fruit, and any fruit that does form remains small, becomes mottled or necrotic, and has delayed maturity. In greenhouse tomatoes, leaf chlorosis and subsequent mottling is easily observed, along with plant stunting. In field tomatoes, if plants are infected when they are young, the mosaic symptoms can be slightly masked by leaf deformation and upward cupping or rolling. If field tomatoes are infected when they are slightly more mature, leaves are less likely to become deformed, so mosaic symptoms are more obvious.
The primary source of CMV infection is from infected weed or crop hosts bordering a field. CMV is vectored by at least 75 species of aphid in a non-persistent manner, meaning that the virus does not remain in the aphid for more than a few hours. Aphids pick up the virus in under 1 minute while feeding and will then spread the virus to any susceptible hosts it feeds on while the virus persists inside its stylet. The length of time the virus persists within the aphid depends on many factors, including aphid characteristics, virus strain, environmental conditions, and weather. The virus is also easily transmitted mechanically. There is no evidence that the virus is seed-borne in any vegetable hosts, but it has been reported to be seed-borne in other hosts.
- Plant resistant cultivars when available. Resistant and tolerant cucurbit and pepper cultivars are available but there are no resistant tomato cultivars.
- Insecticides are not generally useful for controlling CMV because it does not persist within the aphids for long enough. Insecticides can sometimes irritate aphids into moving and probing plants more rapidly and can result in faster spread of the virus.
- Mineral oil or rapid-acting insecticide sprays can be effective.
- Use cultural practices to delay the arrival of aphids into your crop:
- Use reflective mulches to deter aphids
- Isolate fields with taller, non-susceptible crop borders (e.g. corn) to delay arrival of aphids into field and to act as depositories for virus
- Time planting to avoid exposing young plants to high aphid populations (e.g. during aphid migrations)
Crops affected by this disease include:
- Cucumber, Muskmelon, and Watermelon
- Pumpkins, Squash, and Gourds
- Tomato, Field
- Tomato, Greenhouse
–Written by G. Higgins, October 2016
How to Manage Pests
UC Pest Management Guidelines
| All peppers pests | All crops | About guidelines |
Pathogen: Cucumber mosaic cucumovirus (CMV)
(Reviewed 12/09, updated 11/12)
In this Guideline:
SYMPTOMS AND SIGNS
Symptoms on plants with cucumovirus mosaic diseases can vary, but in general, plants show an overall lighter color along with mosaic patterns (alternating light and dark green areas) on at least some leaves, especially on the younger leaves. Often, the main leaf vein is distorted and somewhat zigzag in appearance. Plants generally show stunting, leaf curling, and mosaic, and mature leaves can develop necrotic areas shaped like oak leaves. Fruit may be malformed and have conspicuous concentric rings or spots. It can be difficult to accurately differentiate plants affected by Cucumber mosaic cucumovirus from those affected by the potyviruses. In general, Cucumber mosaic cucumovirus infections are more severe than infections by the potyviruses. However, mixed infections are very common, and this virus and one or more of the potyviruses can simultaneously infect plants.
COMMENTS ON THE DISEASE
Cucumber mosaic cucumovirus is spread from plant to plant by aphid vectors; many aphid species are competent vectors. Aphids transmit Cucumber mosaic cucumovirus while probing the leaf tissues. Once an aphid acquires Cucumber mosaic cucumovirus, it retains the ability to transmit the virus for only a short time (minutes to hours); the spread of the virus is thus local and very rapid within fields. In general, field spread is related to overall aphid activity, not to the presence of colonizing aphids.
Several strains or pathogenic variants of this virus exist. This virus has a tremendously wide host range among broadleaf crop and weed species, and thus, eliminating alternate sources of inoculum is not a feasible management strategy.
No good sources of Cucumber mosaic cucumovirus resistance in peppers are currently available. Efforts are under way to develop resistant cultivars, both through traditional plant breeding and with biotechnology. Eliminating weeds and using reflective mulches to repel the insect vector may reduce the incidence of this disease.
Chemical pesticide strategies are not effective. Insecticides directed at controlling the aphid vectors are not effective in preventing this virus because they cannot kill the aphids before transmission occurs; however, growers should still attempt to manage vector populations when possible (for more information, see GREEN PEACH APHID).
UC IPM Pest Management Guidelines: Peppers
UC ANR Publication 3460
Acknowledgment for contributions to Diseases:
B. W. Falk, Plant Pathology, UC Davis
Top of page
Viruses of cucurbits
What causes viruses
- All of the mosaic viruses can infect all of the cucurbit crops including melon, cucumber, pumpkin, summer and winter squash. In addition, many of the mosaic viruses can also infect common weeds.
- Squash mosaic virus will infect weeds in the Chenopodiaceae family like common lambsquarters, maple leaf goosefoot, Russian thistle and kochia.
- Watermelon mosaic virus infects legumes like clover.
- Cucumber mosaic virus can infect plants from over forty families, including vegetable crops like tomato, lettuce and spinach, flower crops like gladiolus, petunias, impatiens and rudbekia, and a wide variety of weeds.
- All of the mosaic viruses can also infect weeds in the cucurbit family.
- Aphids transfer most of the viruses that infect cucurbits with the exception of SqMV, a virus transmitted by both striped and spotted cucumber beetles.
- Aphids feed on virus-infected plants (weeds or crop) and then transfer the virus when they feed on a new plant.
- Perennial weeds allow the virus to survive from season to season in a field.
- Viruses can transfer from plant to plant on the hands and tools of workers through infected sap.
- Squash mosaic virus can come on infected seed. The other mosaic viruses rarely transfer on seed
- Once in the plant, viruses move systemically through the tissue infecting leaves, vines and fruit.
The Plant Doctor – Tobacco Mosaic Virus
Tobacco mosaic virus is the oldest identified plant virus. It was first recognized because of how easily it infects plants, its noticeable symptoms, and its persistence. It is not as common in Mississippi as other plant viruses, such as tomato spotted wilt virus that causes blackening and ring spots on many plants, or the mosaic viruses that mottle the leaves of cucurbit and blackeyed pea crops.
The tobacco mosaic virus attacks plants in the families that include tomato, pepper, eggplant, tobacco, spinach, petunia, and marigold. Many modern vegetable varieties have been developed to resist this virus. Resistance to TMV is usually stated as “TMV” or sometimes just “T.” Often you must refer directly to the grower’s catalog to determine if TMV resistance is present because it is freqently not labeled on the packaging.
Symptoms vary somewhat with the strain of the virus. Infected plants are usually mottled, stunted, and sometimes distorted. On tomatoes, the virus frequently causes light and dark green mottled areas on the leaves. The dark green areas tend to be thicker than the lighter portions of the leaf. Young growth is usually stunted, with distorted leaves curling down. Some strains produce mottling and streaking, and death of the fruits.
The virus moves to new plants by grafting, in seed coats from the infected mother plant, and by contact with infected plants or plant sap. These facts are very important for a grower to understand, so examples will be used to demonstrate how easily this virus spreads.
Cultivation, pinching, or picking of plant parts spreads virus-infested plant sap from infected to healthy plants. A controlled study showed that a razor blade used to make a single cut in a TMV-infected petunia plant passed the virus to 20 healthy petunia plants before the virus was exhausted on the razor blade.
Slight contact may also transmit the virus. It has been shown that watering nozzles that touch infected plants and are then allowed to touch uninfected plants will transmit the virus. The author was taking weekly pictures of uninfected plants and plants infected with a close relative of TMV. Occasionally, the tripod would LIGHTLY brush a leaf. By the end of 10 weeks, almost all plants were infected with the virus.
Seeds from infected plants may also carry the virus. The earlier the age by which the mother plant is infected, the more likely the seed coat will be contaminated by the virus. When the seed germinates, the virus may enter the seedling by small cuts caused by transplanting, handling, or in the germination/emergence process. Tobacco seeds and tomato seeds are routinely disinfested with either trisodium phosphate or calcium hypochlorite, respectively, to prevent spread. Saving your own seeds is not cost effective when cleaning up an infection.
Tobacco products commonly contain the virus. This means that people who use tobacco products, especially those who roll their own cigarettes, should wash their hands thoroughly with detergent soap before handling plant material. Whole milk or 20 percent (weight to volume) powdered non-fat skim milk with a surfactant such as 0.1 percent Tween 20 is slightly more effective than detergent soap.
The virus is very persistent on bench tops and other materials. It can be infective as long as 8 years on bench tops and 50 years in dried plant material. Cleaning a growing operation after infection with this virus or its relative, tomato mosaic virus, requires patience and attention to detail.
You should carefully clean and disinfest benches, equipment, and disposal areas. First remove soil that hasbeen used to grow infected plants, then remove leaves or other plant debris, whether living or dead. The soil probably holds infected pieces of roots. Dead leaves, even if they have dried and crumbled into a powder, may spread the virus later. It is a good idea to vacuum any remaining plant parts and contaminated soil after you take the trash off site.
Everything should be disinfested. A solution of 10 percent household bleach in contact with the surface for 1 minute has been shown to be the least expensive and an effective means of killing the virus on contaminated tools. Even a little bit of dirt will inactivate the bleach, so make sure all surfaces are clean before disinfesting. Remember to clean and disinfest any tools such as hoses, nozzles, pruners, and plant stakes.
As with all viruses, you cannot save the plant once it is infected. Bag infected plants, then remove them from the operation and destroy them. Control perennial weeds such as horsenettle and jimsonweed, which may act as hosts.
Information Sheet 1665 (POD-07-18)
By Dr. Alan Henn, Extension Professor, Entomology and Plant Pathology.
Cucumber Mosaic Virus Symptoms And Treatment
Cucumber mosaic disease was first reported in North America around 1900 and has since spread worldwide. Cucumber mosaic disease isn’t limited to cucumbers. While these and other cucurbits can be stricken, Cucumber Mosaic Virus (CMV) regularly attacks a wide variety of garden vegetables and ornamentals as well as common weeds. It’s so similar to the Tobacco and Tomato Mosaic Viruses only an expert horticulturalist or laboratory testing can distinguish one from the other.
What Causes Cucumber Mosaic Disease?
What causes Cucumber Mosaic disease is the transfer of the virus from one infected plant to another through the bite of an aphid. The infection is acquired by the aphid in just one minute after ingestion and is gone within hours. Great for the aphid, but really unfortunate for the hundreds of plants it can bite during those few hours. If
there’s any good news here it’s that unlike some other mosaics, Cucumber Mosaic Virus can’t be passed along through seeds and won’t persist in plant debris or soil.
Cucumber Mosaic Virus Symptoms
Cucumber Mosaic Virus symptoms are rarely seen in cucumber seedlings. Signs become visible at about six weeks during vigorous growth. The leaves become mottled and wrinkled and the edges curl downward. Growth becomes stunted with few runners and little in the way of flowers or fruit. Cucumbers produced after infection with cucumber mosaic disease often turn grey-white and are called “white pickle.” T fruit are often bitter and make mushy pickles.
Cucumber Mosaic Virus in tomatoes is evidenced by stunted, yet bushy, growth. Leaves may appear as a mottled mixture of dark green, light green, and yellow with a distorted shape. Sometimes only part of the plant is affected with normal fruit maturing on the uninfected branches. Early infection is usually more severe and will produce plants with low yield and small fruit.
Peppers are also susceptible to Cucumber Mosaic Virus. Symptoms include the mottled leaves and stunted growth of other mosaics with the fruit showing yellow or brown spots.
Cucumber Mosaic Virus Treatment
Even though botanists can tell us what causes cucumber mosaic disease, they have yet to discover a cure. Prevention is difficult because of the short time between when the aphid contracts the virus and its passing it along. Early season aphid control may help, but there is no known Cucumber Mosaic Virus treatment at the present time. It’s recommended that if your cucumber plants are affected by Cucumber Mosaic Virus, they should be removed immediately from the garden.
A typical mosaic pattern on flue-cured tobacco leaves infected with tobacco mosaic virus.
Photo: Courtesy of JP Krausz
Tobacco mosaic virus (TMV) was the first virus discovered.
In 1889, Martinus Beijerinck, found that ‘tobacco mosaic disease’ was caused by a pathogen able to reproduce and multiply in the host cells of the plant. He called it ‘virus’ (from the Latin virus, meaning poison) to differentiate this form of disease from those caused by bacteria.
Tobacco yield losses
due to TMV are currently estimated at only 1%, because resistant tobacco varieties are routinely grown. However, TMV affects other crops, and losses of up to 20% have been reported in tomatoes.
TMV can be a major problem because, unlike most other viruses, it does not die when the host plant dies and can withstand high temperatures. Thus, the virus can survive on implements, trellis wires, stakes, greenhouse benches, containers and contaminated clothing for many months.
It can also survive in crop debris on the soil surface and infect a new crop planted on contaminated land.
Tobacco products, particularly those containing air-cured tobacco, may carry TMV too.
The virus cannot be transmitted in the smoke of burning tobacco, but smokers, especially those who roll their own cigarettes, could possibly carry the virus on their hands and transmit it to healthy plants.
Sap-feeding insects such as aphids cannot transmit TMV. However, chewing insects such as grasshoppers and caterpillars do occasionally transmit the virus. They are not considered important vectors, however.
Tobacco mosaic virus is usually spread from plant to plant via ‘mechanical’ wounds caused by contaminated hands, clothing or tools such as pruning shears and hoes. This is because TMV occurs in very high concentrations in most plant cells. When plants are handled, the tiny leaf hairs and some outer cells are inevitably damaged and leak sap onto hands, tools and clothing.
Seeds from infected plants can also carry the virus on their seed coats. The earlier the age at which the mother plant is infected, the more likely it is that the virus will contaminate the seed coat during seed harvesting. When the seed germinates, the virus may enter the seedling through small cuts caused by transplanting and handling, or during the germination/emergence process.
Once inside the plant, the virus releases its genetic code (RNA). The plant mistakes this for its own RNA, and starts to produce viral proteins.
The virus then spreads to neighbouring cells through microscopic channels in the cell walls (plasmodesmata), and eventually enters the translocation system of the plant (xylem and phloem). From here, it spreads to the entire plant.
Signs and symptoms
Symptoms first appear about 10 days after infection. The plants do not usually die, but growth can be seriously stunted. In the case of tomatoes, certain TMV strains can cause deformed fruit, non-uniform fruit colour and delay ripening.
Specific symptoms depend on the host plant, age of the infected plant, environmental conditions, the virus strain and the genetic background of the host plant.
However, common signs include mosaic-like patches (mottling) on the leaves, curling of leaves and the yellowing of plant tissues.
Managing the virus
No chemicals can cure a plant infected with a virus, and TMV is no exception. As mentioned before, however, resistant plant varieties are available.
You will need to consider adaptability, potential yield and resistance to other important diseases when selecting varieties.
Ultimately, effective TMV management involves using virus-free seedlings or plants and implementing strict hygiene procedures:
- Use new potting mix and new or thoroughly cleaned seedling trays when growing seedlings;
- If infected plants are discovered, either remove and destroy the plants and restrict access to the area, or always work in the affected area last and decontaminate yourself and your equipment afterwards;
- Remove all crop debris from the land, seedling production beds and benches in greenhouses;
- Place tools in a disinfectant solution for at least 10 minutes and rinse thoroughly with tap water;
- Disinfect door handles and other greenhouse structures that may have become contaminated by wiping thoroughly with recommended disinfectants;
- Thoroughly wash your hands with recommended disinfectants, such as carbolic soap, or a mixture of non-fat milk powder at 20% weight/vol, 10% bleach, and 70% ethanol, after handling tobacco products or TMV-infected plants. Make sure that the solutions are fresh, and replace regularly (it is recommended that the bleach solution be replaced every four hours).
If you are a seedling producer, ensure that greenhouses are within a clean zone and control the movement of people, plants, vehicles and materials into the greenhouse areas.
Treat each greenhouse as a separate unit, with protective clothing, tools, gloves and bins in each. These items should not be moved between units.
The ARC’s Industrial Crops unit (Rustenburg) has a virus diagnostic laboratory and conducts diagnostic services for nurseries and farmers.
Email Phillip Mphuti at .