Turnip mosaic virus (TuMV) can be a severe disease on cabbages and other types of brassicas.
Many weeds are hosts to this virus.
This makes the situation worse for growers of cole crops, since aphids are a key source for this virus. The weeds can harbor both the aphids and the virus.
Since there is no cure for turnip mosaic virus, control is of paramount importance.
We at Gardener’s Path will describe the many facets of this virus and how to control it.
What You Will Learn
Types of Plants Affected
Turnip mosaic virus has a phenomenally wide host range – at least 318 species of plants in 43 families! And it infects plants all over the world.
Most cruciferous vegetables are susceptible to this virus. Among them, TuMV is the most severe on turnip, radish, mustard, and Chinese cabbage.
Hosts in other families include spinach, beets, lettuce, rhubarb, and tobacco.
While the yield losses for plants infected late in the season are usually low, TuMV can be devastating if it infects its hosts early in the season.
If it strikes in the seedbed or soon after transplanting, losses can be as high as 75%.
TuMV can infect the whole plant.
The symptoms of this disease vary depending on which host it infects and the stage of growth of the plants.
Symptoms on the young leaves include yellow round spots.
Cabbage, broccoli, and cauliflower leaves develop light green circular lesions that are up to five inches wide.
The tissue in these lesions dies as the infection progresses. Even worse, the lesions may join together and result in the complete loss of leaves.
The plants may be stunted and senesce prematurely.
Cabbage plants may develop dead spots on the outer leaves that occur throughout the whole plant.
Cabbages can also develop turnip mosaic virus during storage, although the disease is only visible on the internal leaves.
Turnip, Mustard, and Radish
Common symptoms of infection in these plants include leaf distortion, stunting, and blisters.
In addition, turnips, radishes, and mustards may develop the classic symptoms of the disease – mosaics – variegated patterns of dark and light areas.
The symptoms often occur on one side of the plant and include the death of the veins and dead spots on the head leaves.
Spread of Turnip Mosaic Virus
Unfortunately, a wide variety of aphids can transmit TuMV by feeding on a plant for less than a minute.
Particular threats include green peach, turnip, and cabbage aphids.
Winged aphids typically spread the infection over a thousand feet.
The aphids are more likely to travel downwind, so weather conditions have an enormous effect on the spread of this virus.
Aphids reproduce and spread more widely when it is warm and dry (68-82 F). Therefore, the aphids spread the virus more rapidly under these conditions.
Plants are less likely to become infected in cool, windy, and wet weather.
Once a crop has been infected, aphids can rapidly spread the disease between plants if they are not controlled.
In addition, the virus can be spread mechanically, such as using infected equipment – or even your hands.
There is no evidence of the transmission of turnip mosaic virus by seeds.
Mixed Infections with Cauliflower Mosaic Virus
Cauliflower mosaic virus often infects cabbage and other cole crops when they are already infected with TuMV and enhances the severity of the infection.
In cool weather, this combination of diseases causes severe stunting and vein clearing.
Stunting and mottling are more common in warm weather.
Cauliflower mosaic virus is also spread mechanically and by aphids. However, unlike turnip mosaic virus, it only infects members of the brassica family.
Eliminating aphids and weeds are the major ways to control TuMV.
You should focus on the elimination of weeds in the brassica family like wild mustard and wild radish, although other types of weeds can also serve as hosts for TuMV.
If you are growing cabbage from seed, locate the bed away from fields that have weeds in them. (And do not plant in soil that previously harbored an infected crop.)
You may want to consider:
- Discarding the plants from the outer rows of the seedbeds
- Locating your transplant beds away from the crops you are growing for harvest or sale
- Killing the aphids with insecticides is an option that you may want to consider. However, some sources advise that insecticides are ineffective at controlling this disease.
- If you are using equipment, you should use it in a new field before you move to an old one.
- Incorporate the remains of the plants into the ground as soon as you harvest them.
- And frequently wash your hands with soap and water while you work among your crop!
If you live in an area that frequently suffers from turnip mosaic virus, you should consider growing Danish cabbage varieties. Reports suggest that they have some resistance against this virus.
A Sporadic but Potentially Deadly Disease
Turnip mosaic virus can be a highly serious disease of cabbage, other cruciferous vegetables, and plants like tobacco.
And if this isn’t bad enough, the course of the disease is often complicated by cauliflower mosaic virus, which can simultaneously infect and greatly worsen the symptoms.
Aphids are the primary agents that spread both types of viruses, and both the pathogens and the aphids can live on weeds near your crop.
Have you suffered through an epidemic of turnip mosaic virus? If so, let us know how your plants fared in the comments.
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About Helga George, PhD
One of Helga George’s greatest childhood joys was reading about rare and greenhouse plants that would not grow in Delaware. Now that she lives near Santa Barbara, California, she is delighted that many of these grow right outside! Fascinated by the knowledge that plants make chemicals to defend themselves, Helga embarked on further academic study and obtained two degrees, studying plant diseases as a plant pathology major. She holds a BS in agriculture from Cornell University, and an MS from the University of Massachusetts Amherst. Helga then returned to Cornell to obtain a PhD, studying one of the model systems of plant defense. She transitioned to full-time writing in 2009.