Since the middle and late September this year, the combined impact of the "West China Autumn Rain" and autumn floods has led to persistently high soil moisture in the main winter rape - producing areas such as Southwest China and the middle and lower reaches of the Yangtze River. This has created favorable conditions for the occurrence and spread of various pests and diseases, including seedling blight (root rot), damping - off disease, and cabbage leaf beetle. The seedling stage is a crucial foundation - laying period for the growth and development of winter rape, and the effectiveness of pest and disease control directly affects the subsequent growth, yield, and quality of the crop. To accurately respond to the current pest and disease control situation and consolidate the foundation for a good rape harvest, the National Agricultural Technology Extension and Service Center has specially formulated and issued the Technical Guidance on Pest and Disease Control for Autumn - sown Winter Rape Seedlings in 2025, providing scientific control guidance for growers in the producing areas.

Clarifying Key Control Objects for Targeted and Precise Efforts

In view of the current occurrence characteristics of pests and diseases at the seedling stage, the guidance clearly defines the key and secondary pest and disease control objects, providing a basis for precise prevention and control measures. Among them, the core control list for the seedling stage includes diseases such as seedling blight (root rot), damping - off disease, sclerotinia stem rot, clubroot, and downy mildew, as well as pests like aphids and cabbage leaf beetles. At the same time, secondary diseases such as black rot, white spot disease, and black spot disease, as well as pests including underground pests, cabbage caterpillars, diamondback moths, and flea beetles, should also be taken into account. A prevention and control pattern featuring "clear priority and comprehensive coverage" should be established to prevent secondary pests and diseases from developing into major hazards due to inadequate control.

Implementing Multi - dimensional and Comprehensive Measures to Build a Control System

Based on the plant protection principle of "prevention first and comprehensive control", the guidance establishes a full - chain pest and disease control technology system covering variety selection, agricultural management, seed treatment, and chemical control, forming multiple lines of defense against pests and diseases.

Scientific Variety Selection to Build a Defense Line: Resistant Varieties Are the Foundation

Variety resistance is the first line of defense against pests and diseases. All regions should select high - quality rape varieties that are dense - tolerant, high - yielding, lodging - resistant, and disease - resistant (tolerant) in accordance with local conditions to reduce the risk of pests and diseases from the source. For areas severely affected by clubroot, the guidance specifically recommends resistant (tolerant) varieties such as Huayouza 62R, Huayouza 5R, Huayouza 115R, Shengguang 165R, and Zhongyou 926. It also suggests appropriately delaying the sowing date to further reduce harm by avoiding the peak period of the disease.

Strengthening the Foundation through Agricultural Control: Ecological Regulation to Reduce Populations

Agricultural control inhibits the breeding of pests and diseases from an ecological perspective by optimizing planting patterns and field management. In areas where sclerotinia stem rot frequently occurs, paddy - upland rotation or rotation with gramineous crops such as barley and wheat should be implemented when conditions permit. This changes the field ecological environment, effectively reducing the stock of pathogenic bacteria and the base number of pest populations, and fundamentally reducing the occurrence of pests and diseases. For areas severely affected by sclerotinia stem rot, biological agents such as Coniothyrium minitans can be used for soil treatment to inhibit the germination of sclerotia. In areas severely affected by clubroot, calcium cyanamide can be applied for soil treatment to specifically reduce the harm of soil - borne diseases.

Strict Seed Treatment: Early Protection for Seedlings

Seed treatment is a key pre - measure for pest and disease control at the seedling stage, which can achieve the effect of "sowing seeds with pesticides to protect seedlings at the seedling stage". Growers can use seed coatings registered for rape for seed pelleting or dressing. Pesticides should be selected accurately according to control needs: thiamethoxam and other pesticides can be used for pelleting or dressing to control seedling pests, while hymexazol and other pesticides can be used to control diseases such as seedling blight. A protective barrier is formed through pesticide coating to effectively resist the invasion of pests and diseases at the seedling stage.

Chemical Control to Make Up for Shortcomings: Precise Pesticide Application to Improve Efficiency

When pests and diseases occur sporadically in the field, chemical control should be carried out in a timely manner to prevent the spread of the disease. For disease control, when sclerotinia stem rot occurs sporadically, pesticides such as prothioconazole, carbendazim, procymidone, prochloraz, and fluxapyroxad can be used for spray control. The pesticide solution should be sprayed on the base of the plant stems, which can also control seedling blight and damping - off disease. For downy mildew control, pesticides such as ethyl allicin and zineb can be used for spray control. For pest control, biological agents such as Metarhizium anisopliae CQMa421 or pesticides like deltamethrin and thiamethoxam can be used to control seedling aphids; deltamethrin, lambda - cyhalothrin, and other pesticides can be used to control lepidopteran pests such as cabbage caterpillars and diamondback moths; rotenone, thiamethoxam, and other pesticides can be used to control flea beetles; and phoxim and other pesticides can be applied in furrows to control underground pests, which can also control cabbage leaf beetles. To improve the comprehensive control efficiency, plant growth regulators such as brassinolide, ferrous dihydroporphyrin, kinetin, or paclobutrazol can be added during spraying to enhance the stress resistance and pest - disease resistance of rape.

Currently, it is the critical period for pest and disease control at the winter rape seedling stage. Growers in all regions should combine the actual occurrence of pests and diseases in their local areas, strictly follow the technical guidance, scientifically coordinate various control measures, make precise efforts, and implement comprehensive measures. This will effectively strengthen the growth defense line of winter rape at the seedling stage and lay a solid foundation for a bumper harvest of rape in the coming year.