Common leaf spot disease of geranium

Geranium leaf spot is a common disease in spring and summer. It is most likely to occur in high temperature and rainy season, which often causes most of the susceptible leaves to die and fall off. When the stem was infected, it blackened, wilted and rotted, and the vascular bundles browned and blackened at the base. Cuttings can not take root, from the stem began to rot, and upward development, resulting in leaf wilting and death.

Symptoms of geranium leaf spot, including black brown disease and brown spot.

Black spot leaves on the primary water stains, semicircular to amorphous, and then round, 2 to 3 mm in diameter, with slightly sunken necrotic spots in the center. The larger plaque is 6 to 10 mm in diameter. Often restricted by the veins of the leaves, it is irregular, dark brown, with concentric patterns and less black mildew layer. The disease spots on the leaf spots are scattered or confluent, and when the leaves are serious, the leaves turn black, wrinkle and die. The disease is more common in the lower old leaves of the plant, but the upper leaves are also vulnerable.

The spot on the leaf of brown spot is round or ovate, 1 to 4 mm in diameter, light brown, grayish white to brick red, with dark brown narrow edges, sometimes slightly bulging under the leaf, with black grains or dark gray mildew layers scattered on the spot.

The pathogens and characteristics of the above two kinds of leaf spot disease are all semi-known subphylum fungi. The amorphous brown spots are caused by the infection of Alternaria. The near-round gray brown spot is caused by the infection of Cercospora, Phytophthora and Cercospora. The above bacteria were first and again infected by conidia in spring and summer by means of wind and rain. Especially in the high temperature and rainy season, diseases are easy to occur. Often by watering, wind and rain, water droplets spatter to the leaves, mainly through knives and other gardening tools contact transmission, invading from the wound. If the environment is humid and the plant grows too dense, it is easy to cause the disease.

Prevention and control methods create ventilation and light transmission conditions, avoid excessive density of plants or branches, reduce humidity, and prevent excessive growth of branches and leaves.

Avoid sprinkler irrigation when watering, in order to prevent sprinkling water to spread germs, should slowly infiltrate along the edge of the basin to prevent excessive watering, stagnant water in the basin, causing rotting roots.

When diseased leaves are found, they must be removed and destroyed in time.

Fertilization should not be excessive, too much nitrogen fertilizer, easy to cause plant leaves to grow, do not blossom or less flowering. More phosphorus and potassium fertilizer should be applied in early spring or early autumn.

Spray 2500 times of 50% benzoate wettable powder or 1 ∶ 1 ∶ Bordeaux before onset. At the beginning of the disease, 50% anthrax Fumei + 80% mancozeb (1 ∶ 1) 1000 times, or 70% chlorothalonil + 70% topiramate (1 ∶ 1) 1000 times, 50% Bao Gong Ke wet powder 1000 times, the above drugs were sprayed 3 to 4 times alternately, once every 7 to 15 days, close before and after sparse, with good control effect.