When is the most suitable time to control Sclerotinia stem rot in rapeseed?

AbstractSclerotinia stem rot in rapeseed can occur throughout the entire growth stage of rapeseed, with a higher incidence rate during the pod-setting stage. The initial control time is at sowing and in the early stages of Sclerotinia stem rot occurrence, when applying biological agents can effectively reduce the number of sclerotia in the field, while the important stage for control is the initial flowering stage and the full flowering stage. Depending on the degree of disease, agents such as Junkeling, carbendazim, jūn hé jìng, and thiophanate can be mixed for control.

I. Timing of Sclerotinia Stem Rot Control in Rapeseed

1. Sclerotinia stem rot in rapeseed can occur throughout the entire growth period of rapeseed, with a relatively high incidence rate during the pod-setting stage. In southern China, where rapeseed is sown in winter, a small number of Sclerotinia stem rot cases generally occur from October to December, while the vast majority of severe cases occur from March to April of the following year.

2. In northern China, where rapeseed is sown, Sclerotinia stem rot generally occurs from March to May. In recent years, due to relatively abundant summer rainfall, the incidence rate of Sclerotinia stem rot has also been relatively high in spring rapeseed planted in the northwest.

3. Therefore, biological agents can be applied at sowing and in the early stages of Sclerotinia stem rot occurrence, which helps reduce the number of sclerotia in the field. The important period for Sclerotinia stem rot control is during the initial flowering stage and the full flowering stage. During this period, depending on the degree of disease, agents such as carbendazim, Junkeling, jūn hé jìng, and thiophanate can be mixed for control.

II. Agricultural Control Measures for Sclerotinia Stem Rot in Rapeseed

1. Plant varieties with strong disease tolerance. First, carry out paddy-upland rotation, soaking and rotting the sclerotia remaining in the soil through irrigation, thereby reducing sources of infection. Second, promptly handle residual plants. After threshing rapeseed, treat the stems, branches, leaves, and pod husks separately or place them in the field for composting.

2. Third, deep plow the soil for sterilization. Choose to deep plow in autumn, then carry out 1-2 times of intertillage and hilling in spring, which can eliminate and bury apothecia. Fourth, treat the seeds. Through methods such as screening and chemical seed dressing, eliminate sclerotia and kill pathogens on the seed surface, then proceed with sowing.

III. Chemical Control Measures for Sclerotinia Stem Rot in Rapeseed

1. Along with agricultural control, chemical agents can also be used for control, which can control and reduce the incidence rate of Sclerotinia stem rot. To improve control effectiveness, the dosage must be well controlled, and suitable drugs must be selected for control. At present, the main commonly used agent varieties include various fungicide compound pesticides such as Junkeling, jūn hé jìng, carbendazim, and thiophanate.

2. Since rapeseed is susceptible to Sclerotinia stem rot during the flowering stage, 1 application of the agent can be sprayed at the initial flowering stage, and a second application should be made 7-10 days later. After spraying twice, if continuous rainy weather occurs, another application of the agent is needed, which helps improve control effectiveness. When applying, the water dilution amount is 50-60 kg, and a relatively coarse spray can be used as appropriate. Spraying should cover from the flowers to the basal stems, so that a protective layer of the agent forms on the plant surface.