Red blight of spruce and its control

In recent years, with the increase in the number of spruce planting, spruce red blight occurred seriously, and some closed forest belts were as high as 50%, seriously weakening the tree potential and even causing dead trees. The incidence of the disease is rapid, from the bottom of the tree to the tree, the outer edge of the crown to the inner chamber, the base of compound leaves to the top. As many as 10 days, as little as 1 week, can cause the whole plant leaves to turn yellow, and then fall off.

The disease is caused by fungi. When the temperature suddenly changes and the humidity increases, the tree will become sick. The diseased leaves appear small brown spots at the beginning, then expand into dark brown, and produce many protruding black mildew spots on the diseased spots when it is wet in the rain, that is, the conidiophores and conidiophores on them. It can spread to the trunk epidermis by wind and rain, directly invade the green main stem or extend from the twigs and leaves to the green main stem, forming brown and reddish brown slightly sunken ulcer spots. After the development of this kind of spot, it surrounds the stem for 1 week, then all the upper parts die. Sometimes the ulcer spot on the main stem does not expand quickly, but it does not heal, and gradually enters the trunk with the growth of the trunk, forming a ditch disease. Although the tree is immortal, it is vulnerable to wind break.

Prevention and control methods: "prevention first, scientific prevention and control", strengthen management, protect roots and leaves, enhance resistance, strengthen tree potential. Select varieties with strong disease resistance, such as green fir and so on. If the soil quality requires medium fertility, choose the soil with good permeability. The rational use of fertilizer will not damage the dredging roots with a thickness of more than 0.3 cm. Reasonable ploughing and timely irrigation. Try to avoid ploughing in high temperature season to prevent damage to roots. Irrigation is not suitable for 11-14:00 in the hot season.

It is effective to use chemical to control root irrigation and spray at the same time. Spray is when the sap begins to flow before spruce sprouting, spray 5 Baomedo stone sulfur mixture. In early May and August, the mixture of 50% Yisheng 600x solution plus Zengwang, 70% methyl topiramate 1000 fold solution and botanical biological fungicide was sprayed alternately, once every 5 days, for a total of 2 times. Root irrigation is that after spitting new leaves and stopping growth, the roots are irrigated alternately with 55% Dexong 700 times solution and 50% Jinxiaokang 1000 times solution, once every 3 days, for a total of 2 times. The above drugs can be halved as preventive treatment. In order to control the disease, the diseased leaves which have been withered and yellow are buried or burned.