Symptoms and prevention of black spot disease

Symptom

Leaves, petioles, twigs and pedicels can all be damaged, but mainly damage leaves. There are two types of symptoms: one is the appearance of reddish brown to purplish brown spots on the leaf surface at the initial stage of the disease, which gradually expands into a round or amorphous dark black spot, which is often surrounded by a yellow halo, the edge is radial, and the diameter of the spot is about 3-15 mm. In the later stage, there are small black dots on the plaque, that is, the meristematic bubble plate of the bacteria. In severe cases, the lower leaves of the plant are withered and yellow, and the leaves fall in the early stage, resulting in the death of individual branches, such as black spot of rose.

The other is the appearance of brown to dark brown nearly round or irregular round spots on the leaves, on which black mildew grows, that is, the conidia of the pathogen. In serious cases, the leaves fall early, affecting the growth, such as the black spot of elm leaf plum.

Morbidity regularity

Black spot is the main disease of rose, which occurs widely and causes serious damage. The pathogen overwinters in dead branches or soil in the form of mycelium or conidia. The infection began in the middle and late May of the following year, and the peak period was from July to September. Conidia spread, expand and re-infect by wind, rain or insects.

Rain Water is the main condition for the epidemic of the disease. the disease occurs early and seriously in the year with early and more rainfall. Low-lying stagnant water, poor ventilation, lack of light, improper fertilizer and water are conducive to the disease.

Prevention and cure method

① selected excellent disease-resistant varieties.

② will remove dead branches and fallen leaves after autumn and burn them in time.

③ should strengthen cultivation management, pay attention to shaping and pruning, ventilation and light transmission.

When ④ new leaves unfold, spray 50% carbendazim wettable powder 500-1000 times, or 75% carbendazim 500 times, or 80% Dysen zinc 500 times, once every 7-10 days, 3-4 times in a row.