Turnip Mosaic Virus (TuMV) poses a significant threat to crops like cabbage, radish, mustard, and other brassicas. The virus has a wide range of hosts, including numerous weeds, which exacerbates the problem for growers, as aphids are key vectors for its transmission. Since there is no cure for TuMV, controlling its spread is crucial for minimizing crop damage.
Key Points
- Plant Affected: TuMV infects over 318 plant species, including turnips, radishes, mustard, Chinese cabbage, spinach, beets, lettuce, rhubarb, and tobacco.
- Symptoms: Symptoms vary by plant and growth stage but typically include yellow spots on young leaves, light green lesions on brassica crops, and stunting. In severe cases, leaves may die or join together, leading to complete leaf loss.
- Damage: While late-season infections cause minimal yield loss, early infections can devastate crops, with losses reaching up to 75% in seedbeds or shortly after transplanting.
Spread of Turnip Mosaic Virus
TuMV is spread primarily by aphids, which can transmit the virus after feeding for less than a minute. Key aphid species include the green peach, turnip, and cabbage aphids. Winged aphids can travel long distances, spreading the virus across fields. The virus is more likely to spread in warm, dry weather (68-82°F), which promotes aphid reproduction and movement. However, in cool, wet, or windy conditions, the spread is slower.
In addition to aphid transmission, TuMV can spread mechanically via contaminated equipment or human hands. It’s important to note that the virus is not transmitted through seeds.
Symptoms of Infection
- Cabbage, Broccoli, and Cauliflower: Circular light green lesions that can grow up to five inches wide, causing tissue death and leaf loss.
- Turnip, Mustard, and Radish: Mosaics, where leaves show a variegated pattern of dark and light areas, along with leaf distortion and stunting.
- Chinese Cabbage: Symptoms often affect one side of the plant, with vein death and dead spots on the head leaves.
Control Methods
The most effective way to control TuMV is by managing aphid populations and eliminating weed hosts. Here are some strategies for minimizing the risk:
- Aphid Control: Insecticides can be used to target aphids, although their effectiveness can vary. Some sources recommend focusing on cultural practices like crop rotation and early detection of aphids.
- Weed Control: Weeds, especially those in the brassica family (wild mustard, wild radish), are primary hosts of TuMV. Regularly remove weeds from fields and avoid planting crops in areas previously infested with infected plants.
- Field Management: For seedbed planting, locate your fields away from areas with high weed presence. Consider discarding outer rows in seedbeds and setting transplant beds apart from harvestable crops. Use equipment in a new field before moving it to infected fields.
- Cultural Practices: Incorporate plant residues into the soil immediately after harvest to reduce potential viral buildup. Practice regular hand washing when
- working with crops to avoid spreading the virus.
Consider Growing Resistant Varieties
If TuMV is prevalent in your area, consider growing varieties of cabbage that are resistant to the virus, such as Danish cabbage, which has shown some resistance in reports.
A Serious but Manageable Threat
Turnip Mosaic Virus can be a sporadic yet deadly disease for brassica growers, often compounded by other viruses like Cauliflower Mosaic Virus. Early and consistent management of aphids and weeds, along with careful field practices, is key to minimizing its impact. By taking these preventive measures, growers can protect their crops and reduce the potential for large-scale losses.