Pine seedling leaf blight (â—Cereospora pini-densiflorae Hori et Nambuâ—)
The disease often develops gradually from the lower needles of the seedlings. The diseased leaves begin to appear yellow-brown spots, then expand into segmented spots, and wither to death, the color is dark, and many black spots are formed on the lesions. Although the leaves are dry, they do not fall off. If all the needles are infected, the seedlings die. In East China, pine leaf blight usually begins in mid-August, and it is prosperous from September to October. It gradually weakens after November. Diseases are most likely to be endemic in years when there is more rain.
Effective measures for raising seedlings should be taken to improve the environmental conditions, and the disease resistance of seedlings should be strengthened, supplemented by sterilization of pesticides, and the occurrence of diseases should be reduced or prevented. The specific measures are as follows:
1. In the nursery where the disease develops year after year, rotation should be carried out, and rotation of coniferous broad-leaved trees can reduce the disease. For nurseries that can only be used as continuous crops, the diseased seedlings should be completely removed in winter to reduce the number of pathogens.
2. Deep plowing in winter will bury the remnants of the diseased plants in deep soil, apply enough basal fertilizer, and pay attention to timely irrigation for drought prevention in the summer. It is best to divert water to the trails to infiltrate the seedbed.
3, grow dense seedlings, should be time and weak seedlings, so as to avoid the formation of disease centers, and make the seedlings grow robustly.
4, from the beginning of August with 1:1:100 ~ 200 (copper sulfate: quicklime: water) Bordeaux spray to prevent disease, spraying once every two weeks, the amount of 75 to 100 kg per mu; or Baume 0 .2 ~ 0.3 degrees of lime sulfur mixture, the same amount as above. The onset of the disease was controlled with a 50% thiotrexate 800-fold solution and the effect was significant.
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