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How to prevent and control spruce snow blight? A detailed guide to practical methods

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Snow blight damages spruce needles, turning diseased needles reddish-brown. Snow blight develops under snow; ascospores invade spruce needles covered by snow, mature each year from September to October, and then spread by wind and rain. Observations show that in young stands after artificial regeneration and reforestation, the dense planting of the past created a "hand-in-hand" situation, and once the disease breaks out it spreads especially severely; after half of a plant's needles are infected, lose their green color and turn reddish-brown, the entire plant dies. The uncrowned regeneration land at Tekes Forest Farm covers nearly 2666 hectares. In order to ensure the

Snow blight damages spruce needles, turning diseased needles reddish-brown. Snow blight develops under snow; ascospores invade spruce needles covered by snow, mature each year from September to October, and then spread by wind and rain. Observations show that in young stands after artificial regeneration and reforestation, the dense planting of the past created a "hand-in-hand" situation, and once the disease breaks out it spreads especially severely; after half of a plant's needles are infected, lose their green color and turn reddish-brown, the entire plant dies. The uncrowned regeneration land at Tekes Forest Farm covers nearly 2666 hectares. In order to ensure the results of many years of artificial regeneration and reforestation and to let the young trees form a forest as early as possible, we adopted a variety of methods for prevention and control and achieved certain results. The measures taken during the prevention and control process are briefly described below:

I. Silvicultural measures

1. Thinning

After the snow melts and the ground thaws each year, thin out the young trees that have formed a "hand-in-hand" situation, increase their growing space and improve their own disease resistance.

2. Pruning

Before the buds of the young trees open, cut off infected branches and burn them in a centralized manner. The infected parts generally spread from the bottom upward. Cut off all infected branches; after pruning, keep the distance between the lowest branch and the ground at one third of the tree height. On the one hand, this removes the source of infection, and on the other hand it reduces the chance of infection.

II. Chemical control

1. Timing of control

Chemical control is carried out each year from September to October, when the ascospores mature and begin to spread.

2. Fungicides

Use carbendazim 25% and 50% wettable powder, and thiophanate-methyl 50% wettable powder, at a dilution ratio of 1:400.

3. Spraying equipment

Due to terrain limitations, only a knapsack motorized mist duster, model WFB-18, was used; it has all the functions needed for operations on mountain regeneration plots.

4. Direction of travel, spraying direction and wind direction

Spray from the upwind side to the downwind side according to the terrain

III. Summary

The combination of thinning, pruning and chemical control gives the best results in controlling spruce snow blight. Because regeneration plots are limited by water sources and terrain, some diseased plots cannot be treated chemically; adopting the method of pruning twice in three years, once each in the first and third years, can also achieve the expected results. When trees reach 3 m in height, their disease resistance increases, and the phenomenon of infection leading to death will no longer occur.

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