National Agricultural Technology Extension Center: With above-normal winter precipitation and temperatures, oilseed rape fields in the Yangtze River Basin in 2020 should prioritize controlling 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 atmospheric circulation 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, in collaboration with the Oilseed Expert Guidance Group of the Ministry of Agriculture and Rural Affairs, has formulated spring field management guidelines for 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 early to mid-February, with 5–6 kg of urea and 1 kg of potassium chloride per mu; these should be evenly mixed before application, or a compound fertilizer containing equivalent nutrient levels may be used. For vigorously growing rapeseed, it is recommended to delay or omit bolting fertilization and instead adopt topping to achieve “dual-purpose” cultivation while controlling excessive vegetative growth.

Second, clear ditches and manage soil moisture to prevent waterlogging and reduce humidity. In the Yangtze River Basin, paddy‑field rapeseed is subject to relatively high groundwater levels, substantial soil moisture, and moderate soil permeability, all of which hinder 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 spread, potentially leading to widespread outbreaks and rapid dissemination of diseases such as Sclerotinia stem rot. It is essential to promptly clear drainage ditches and maintain unobstructed “three‑ditch” systems to prevent waterlogging caused by frequent rainfall. For late‑sown rapeseed fields, weed pressure tends to be more severe; in areas with heavy weed infestations, early spring applications of herbicides can effectively 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 heighten the risk of a spring outbreak of Sclerotinia disease. We recommend adopting a “one promotion, four protections” strategy: promote vigorous growth and pod formation, and implement preventive measures against Sclerotinia, flower abortion, premature senescence in the later stages, and “rat‑tail” symptoms. Within one week of the onset of flowering, apply appropriate fungicides; where feasible, actively promote the use of drones or large‑scale sprayers to achieve coordinated, integrated pest management, thereby enhancing control efficacy and operational efficiency while reducing costs. In particular, under the “dual‑purpose” cultivation system—where harvesting the stem creates wounds that can exacerbate Sclerotinia incidence—extra attention must be paid to disease 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 the spring thaw. 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 appropriate insecticides 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 collect and thresh with a self‑propelled rapeseed picker‑thresher, or manually pick the pods and then thresh them using a conventional full‑feed rice‑and‑wheat combine harvester. For varieties that exhibit strong resistance to pod shattering and lodging and mature early, employ a rapeseed combine harvester to complete the harvest in a single pass once all plants in the field have fully dried out.

Source: National Agricultural Technology Extension Service Center