How to prevent and control needle blight in Chinese pine seedlings? These measures are essential to know

Chinese pine (Pinus tabuliformis) is a needle-leaved evergreen tree of the pine family (Pinaceae), reaching up to 30 m tall, with a straight trunk and curved, varied branches that from a distance resemble the “Hulk” from American movies. But Chinese pine seedlings are very prone to needle blight, so how do you prevent and control needle blight in Chinese pine seedlings? What specific measures are there?

I. Main damage

The needles of seedlings and young trees of Masson pine (Pinus massoniana), Chinese pine, Huangshan pine (Pinus hwangshanensis), black pine (Pinus thunbergii), lacebark pine (Pinus bungeana) and other pines, and can cause the death of large numbers of seedlings left in the seedbed.

II. Disease symptoms

Pine seedling needle blight first infects the lower needles and gradually spreads to the upper needles. On affected needles, patches of brownish-yellow spots appear segment by segment starting from the needle tip, later gradually turning dark brown to grayish brown. The diseased needles droop after drying out but do not fall off. When the disease spreads to all the needles, the diseased seedlings dry up and die.

III. Occurrence pattern

The pathogen overwinters as mycelium in diseased needles. In the summer of the following year, when environmental conditions are suitable, it produces conidia. The conidia spread with the wind and, upon encountering pine seedlings, can invade the needles and cause damage. Pines sown that year begin to develop the disease in mid-July, with the peak period from August to October, and it gradually stops after November. On diseased seedlings in the second year, conidia are produced as early as early May.

The occurrence of the disease is closely related to environmental conditions. High temperature and high humidity in summer favor infection by the pathogen. Shallow plowing in the nursery, underdeveloped seedling root systems, poor soil water- and fertilizer-holding capacity, and weak seedling growth make the disease more likely. In diseased nurseries, when newly planting pine seedlings, if diseased seedlings are not removed, and deep plowing and soil disinfection are not carried out, the disease often becomes severe. When seedlings are grown too densely, ventilation and air permeability are poor, and the disease spreads easily. Nurseries with soil nutrient deficiency and poor management have severe disease.

IV. Prevention and control measures

1. Remove the source of infection (source of the pathogen): For the few affected plants, pick off the infected needles or pull up the diseased seedlings and burn them in a centralized manner, to prevent the formation of disease centers in the seedling bed and the spread of the disease.

2. Strengthen management: During the seedling growth period, apply fertilizer, water, and loosen the soil, and ensure ventilation and light penetration to reduce humidity. Apply nitrogen, phosphorus, and potassium in a balanced way, and increase the application of organic fertilizer. Ensure that the seedlings grow robustly and enhance their disease resistance.

3. Chemical control: At the early stage of the disease, use Ludun at 500 times dilution (mixed with 300 kg of water), or Youlejing at 800-1000 times dilution (240-300 kg) to spray the needles evenly. When the disease is severe, use Yulinjun at 1000 times dilution (mixed with 100 kg of water) for spraying, once every 7 days or so, for 2 to 3 consecutive times. If used together with the foliar fertilizer Lurun, the effect is even better.