How to control sclerotinia rot in rapeseed cultivation?
What are the harms of rapeseed sclerotinia rot? How to control rapeseed sclerotinia rot? Please give guidance. Harms of rapeseed sclerotinia rot: In the seedling stage of rapeseed, sclerotinia lesions mostly occur at the junction of the root and stem near the ground, forming reddish-brown spots, which later expand and turn pale white, with the tissue becoming wet and rotted, and white flocculent mycelium growing on the surface. After the lesions encircle the stem, ...
What are the harms of rapeseed sclerotinia rot? How to control rapeseed sclerotinia rot? Please give guidance.Harms of rapeseed sclerotinia rot:
In the seedling stage of rapeseed, sclerotinia lesions mostly occur at the junction of the root and stem near the ground, forming reddish-brown spots, which later expand and turn pale white, with the tissue becoming wet and rotted, and white flocculent mycelium growing on the surface. After the lesions encircle the stem, they cause stem rot and seedling death, and many black sclerotia form on the outside of the diseased tissue.
When leaves of adult rapeseed plants are affected, round or irregular water-soaked lesions initially appear, with the center of the lesions grayish-brown or yellowish-brown, the edges dark bluish-green, and slightly concentric rings; the lesion margins fade to green, with a yellow halo on the outer edge. When dry, the lesions crack and perforate; under humid conditions, they expand rapidly, the whole leaf rots, and white mycelium grows on the surface.
When the stem of rapeseed is affected, spindle-shaped light brown water-soaked lesions first appear, slightly sunken, white in the center, with brown concentric rings at the edges. Under humid conditions, the lesions develop very rapidly, and white mycelium grows on the surface. In the late stage of the disease, the stem epidermis breaks, the vascular bundles are exposed in a thread-like manner, the pith becomes hollow, and the plant lodges easily; many sclerotia resembling black mouse droppings form inside the stem. In severe cases, the whole plant dies; lightly affected plants die partially or ripen prematurely, and the seeds are not plump.
After rapeseed petals are infected, they turn pale yellow and later white. After siliques are infected, irregular white spots appear, and small round sclerotia can form inside and outside the siliques. After seeds are infected, the surface is rough, grayish-white, lusterless, or they become irregular shriveled grains.
Control methods for rapeseed sclerotinia rot
1. Agricultural control: Breed and select varieties with relatively strong disease tolerance.
First, implement paddy-upland rotation. Through irrigation, the sclerotia remaining in the soil are soaked and rotted, reducing the source of infection;
Second, handle the residual plants. After threshing rapeseed, treat the stems, branches, leaves, and silique husks separately or put them into paddy fields to compost as fertilizer;
Third, deep plowing to sterilize. Deep plowing in autumn and 1-2 times of intertillage and earthing up in spring can break up and bury the apothecia;
Fourth, seed treatment. Through methods such as screening, winnowing, and chemical seed dressing, eliminate sclerotia and kill pathogens on the seed surface, and sow disease-free seeds.
2. Chemical control: While implementing agricultural control, timely use of chemical agents for control is a key technical measure to control and reduce the harm of sclerotinia rot. Based on years of experience, to ensure the disease control effect, the timing of application must be accurately determined, the fungicide must be correctly selected, and the correct application method must be adopted.
At present, the main commonly used fungicide varieties include carbendazim, jun keling, dimethachlon, thiophanate, and various compounded fungicide pesticides.
Since rapeseed is most susceptible to the disease during the flowering stage, it is very important to apply the first treatment at the early flowering stage. Apply the second treatment 7-10 days later. If continuous rainy days occur after the two treatments, a third treatment should also be applied if possible.
To ensure the disease control effect, when applying, first, consistently use an adequate water volume of 50-60 kg; second, consistently spray with coarse droplets, covering from the flowers to the basal stems everywhere, so that a protective layer of fungicide forms on the plant surface.
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