To prevent and control large-leaf boxwood leaf spot disease, please do these five points!

Large-leaved boxwood, also known as Holly Spear, Holly, Orthoptera, Sylvestris, Shrub or Small Tree. Populus macrophyllum is a temperate and subtropical tree species, which is widely cultivated in China and grows at an altitude of 500 to 1400 m in mountains, valleys, river banks or hillside forests. Large-leaved boxwood is an excellent landscaping tree species, which can be used to plant hedges and background planting materials, or it can be planted in the flower territory alone and turn them into a low giant sphere, which is quite beautiful. However, the large-leaved boxwood is often invaded by leaf spot disease, causing the large-leaf boxwood to fall leaves early and form bald branches, resulting in the death of plants in pieces, causing serious economic losses. The following Xiaobian will make a detailed introduction to the symptoms of the disease, the law of incidence and its prevention and treatment points, hoping to bring help to everyone.

1. Symptom recognition

Leaf spot disease is mainly harmful to the young leaves and old leaves of the large-leaved boxwood, at the beginning of the disease, there are small yellow spots on the leaves, which gradually become yellow-brown spots, expand to nearly round or irregular shape, diameter 4 to 10 mm, the central gray-white, there are light brown concentric wheels, the edges are dark brown slightly raised, and the spots are densely covered with small black mold spots. The lesions pass through the back, but the back is slightly lighter than the front. After the plaque withers, it splits with the healthy part until it forms a perforation. In severe cases, the disease spots are connected into one piece, and the leaves are yellow and fall off.

Second, the law of pathogenesis

Pathogens overwinter on diseased leaves or deciduous leaves in the form of mycelium or ovary, produce conidia in the spring for initial infestation, and then produce a large number of conidia throughout the growing season for multiple re-infections. When it is rainy, wet, frost damaged in spring, or plants are too dense and poorly ventilated, the disease is often severe, resulting in leaf fall. Large-leaved boxwood leaf spot disease is easy to occur with mesophyllum, aphids, etc., which aggravates the disease of the plant. It is easy to cause diseases when the management is extensive, the drainage is not smooth, the planting is too dense, and the ventilation is poor.

Third, prevention and control methods

(1) Eliminate the source of infection: remove the diseased leaves in winter, burn or bury deeply, and eliminate the source of infection.

(2) When planting and raising seedlings, select robust plants to improve disease resistance.

(3) Spray 3 to 5be (Baume degree) stone sulfur compound in spring to eliminate the source of overwintering disease.

(4) Strengthen maintenance management: choose plots with good drainage and moderate fertility to facilitate plant growth, enhance tree potential, and improve disease resistance. Reasonable dense planting, pay attention to ventilation and light transmission, reduce foliar humidity, reduce morbidity. Watering should be appropriate, and drained in time on continuous rainy days.

(5) Chemical control: at the beginning of the occurrence of the disease, you can choose 70% methyl tolbuzin wettable powder 1000 liquid, or 50% carbendazim wettable powder, or 75% bacillus clear wettable powder 500 times liquid for spray prevention and control, chemical agents should be used alternately, sprayed every 7 to 10 days, continuous use of 2 to 3 times the effect is good.