Cabbage virus disease is a significant threat to Chinese cabbage and other cruciferous vegetables. Commonly referred to as "Orphan" or "Cramp," this disease can severely impact plant growth and yield. The symptoms are most noticeable during the seedling stage, before the 6th leaf appears. Affected plants show bright veins and chlorotic streaks along the leaf veins, with curled and distorted leaves. As the plants mature, the leaves become yellow-green with necrotic spots on the veins, and the overall growth is stunted. In severe cases, the roots become underdeveloped and may appear yellowish-brown, making them difficult to remove.
The primary pathogens responsible for this disease include the Turnip Mosaic Virus (TuMV), Cucumber Mosaic Virus (CMV), and Tobacco Mosaic Virus (TMV). TuMV is transmitted by aphids and remains active at temperatures between 55–60°C for 10 minutes. CMV is spherical in shape and becomes inactive at 60–70°C within 10 minutes, also spread by aphids. TMV spreads through mechanical contact, such as human touch or contaminated tools.
The disease cycle involves overwintering in cruciferous crops like cabbage, radish, and spinach. In spring, it spreads via aphids or direct contact with vegetables. In northern regions, the virus persists in underground storage areas during winter, re-emerging in the following season. Greenhouse-grown plants serve as an important source of infection, while in warmer southern areas, the virus circulates year-round.
Aphids play a crucial role in spreading the virus from one plant to another. Studies have shown that in the southern, southeastern, and southwestern directions, intercalary necrotic spots are more common, indicating a strong relationship between aphid activity and virus transmission. Therefore, monitoring aphid populations and their flight patterns is essential for effective control.
To manage the disease, several strategies can be implemented:
1. **Resistant Varieties**: Selecting high-type cabbage varieties with natural resistance can reduce the risk of infection.
2. **Seedling Management**: Careful handling of seedlings is critical. Avoid planting in areas where aphids may be present. Soil should be treated with insecticides to eliminate aphids before transplanting.
3. **Netting Protection**: Covering seedlings with fine mesh nets (40–45 mesh) helps prevent aphid access. White nets are particularly effective since aphids are repelled by this color.
4. **Sowing Timing**: Sowing early, before the summer heat, can help avoid peak aphid activity. However, timing must be balanced to avoid early infection.
5. **Insecticide Application**: Using granules mixed with ash or clay, combined with insecticides like dimethoate or chlorfenapyr, can help control aphid populations before and after sowing.
6. **Chemical Treatments**: Several chemical agents are available, including Virusex (20% copper hydroxide), Plant Disease Spirit (15%), and 83 Activator. These are applied at specific dilutions and intervals to control the virus effectively.
7. **Disease-Free Seed Sources**: Choosing disease-free seeds is vital. Proper selection and storage of seeds ensure healthy plantings.
A simple identification method involves examining the base of the leaves. Healthy plants will have white, tender vascular bundles, while infected ones show yellow or brown discoloration. This technique helps quickly distinguish between healthy and diseased plants.
By combining cultural practices, chemical controls, and careful monitoring, farmers can significantly reduce the impact of cabbage virus disease and protect their crops.
ZHONGSHAN G.H.L. TRADING CO., LTD. , https://www.ghltrade.com