National Agricultural Technology Extension Center: With above-normal winter precipitation and temperatures, oilseed rape fields in the Yangtze River Basin in 2020 should take measures to control Sclerotinia stem rot.

On February 6, 2020, the National Agricultural Technology Extension Service Center and the Oilseed Expert Guidance Group of the Ministry of Agriculture and Rural Affairs issued the 2020 Technical Guidelines for Spring Field Management of Rapeseed in the Yangtze River Basin. The full text of the guidelines is provided below.

Since last autumn and winter sowing, the main rapeseed‑producing areas in the Yangtze River Basin have experienced average temperatures 1–2°C above normal, with winter precipitation significantly higher than usual for this time of year. Favorable climatic conditions have resulted in generally good seedling establishment and a slightly earlier developmental stage. According to meteorological forecasts, with the onset of spring, increased rainfall, rising temperatures, and stronger air currents will create favorable conditions for the occurrence and spread of Sclerotinia stem rot. At the same time, substantial temperature fluctuations may lead to staggered pod set in some early‑maturing and early‑sown rapeseed crops. In light of current crop conditions and prevailing weather patterns, the National Agricultural Technology Extension Service Center, together with the Oilseed Expert Guidance Group of the Ministry of Agriculture and Rural Affairs, has formulated technical guidelines for spring field management of rapeseed in the Yangtze River Basin, emphasizing “promoting spring growth while prioritizing disease prevention and control.”

First, apply additional bolting fertilizer to promote balanced growth. Focusing on last year’s late-sown rapeseed, applying additional bolting fertilizer to promote spring growth is key to this year’s upgrading and transformation of the crop, as well as an important measure for preventing spring cold damage and mitigating premature senescence later in the season. Bolting fertilizer is typically applied in mid‑February; apply 5–6 kg of urea and 1 kg of potassium chloride per mu, mixing them evenly before application, or use a compound fertilizer with equivalent nutrient content. For vigorously growing rapeseed, it is advisable to delay or skip bolting fertilization and instead adopt topping to achieve “dual-purpose” cultivation while controlling excessive vegetative growth.

Second, clear ditches and improve soil aeration to prevent waterlogging and reduce soil moisture. In the Yangtze River Basin, paddy fields planted with rapeseed typically experience elevated groundwater levels and high soil moisture, coupled with moderate soil permeability, which can restrict root development and increase the risk of premature senescence and lodging in the later growth stages. Meanwhile, the high field humidity creates favorable conditions for pathogen proliferation and dissemination, potentially leading to widespread outbreaks and rapid spread of diseases such as sclerotinia rot. It is essential to promptly clear drainage ditches and maintain unobstructed “three‑channel” systems to prevent waterlogging caused by frequent rainfall. For late‑sown rapeseed fields, weed pressure tends to be relatively severe; in areas with heavy weed infestations, early spring applications of herbicides can help suppress weed growth.

Third, implement “one promotion and four preventive measures” to control the damage caused by Sclerotinia disease. Compared with previous years, this winter has seen above‑average precipitation and temperatures, creating favorable conditions for Sclerotinia sclerotiorum to proliferate. Coupled with an earlier developmental stage in rapeseed, these factors could significantly increase the risk of a spring outbreak of Sclerotinia disease. We recommend adopting a “one promotion, four protections” strategy: promote vegetative growth and pod set, and implement preventive measures against Sclerotinia disease, flower abortion, premature senescence in the later growth stages, and “rat‑tail” symptoms. Within one week of the onset of flowering, apply appropriate fungicides for control; where feasible, actively promote the use of drone‑based or large‑scale mechanical spraying to achieve integrated pest management, enhancing efficacy and operational efficiency while reducing control costs. In particular, under the “one crop, dual use” cultivation system, the wounds caused by stem removal can exacerbate Sclerotinia incidence, so extra attention must be paid to its prevention and management.

Fourth, adopt a comprehensive approach to bird control and pest management. Birds are fond of feeding on “double-low” rapeseed; it is recommended to implement bird‑deterrent measures such as placing scarecrows and colorful ribbon strips in the fields after spring begins. Last winter, temperatures were relatively high, If weather conditions become favorable later in the season, aphid damage during the pod‑setting stage may intensify. Timely application of an appropriate insecticide is recommended. Given the migratory nature of aphids, integrated pest management—particularly coordinated, large‑scale control—is the most effective approach.

Fifth, promote mechanized harvesting to reduce losses. Vigorously promote mechanized, staged harvesting of rapeseed to reduce harvest losses, lower the rate of green seeds, and enhance both seed quality and economic returns. For staged harvesting, when approximately 80% of the plants in the field have turned a loquat‑yellow color, use a rapeseed swather or manually cut and lay the plants down; after drying in the field for 5–7 days, either employ a self‑propelled rapeseed pickup‑thresher or, following manual sorting, process the crop with a conventional full‑feed rice‑and‑wheat combine harvester. For varieties that exhibit strong resistance to pod shattering and lodging and mature early, once all plants in the field have completely dried out, harvest them in a single pass using a rapeseed combine harvester.

Source: National Agricultural Technology Extension Service Center