Impatiens powdery mildew and brown spot

Powdery mildew

Symptoms: mainly damage leaves, flowers and stems can also be damaged. Round white mildew spots first appeared on the leaves of impatiens, which generally began to occur in May. After June, the disease spots expanded or multiple disease spots were connected into pieces, each layer thickened to form a white powdery mildew layer, and mildew layers could be produced on the front and back of the leaves. In early autumn, yellow dots were formed in the powder layer, and then gradually deepened and finally dark brown. In serious cases, the leaves died and fell early.

Pathogen and occurrence regularity: the subphylum of atomic cysticercus, powdery mildew caused by monofilament. The ascomycetes are aggregated or scattered, brown, globose, subglobose, parietal cells are large, obvious, irregular. The ascus is oval or ovate, the immature ascus often has a short stalk, and the ascospores are oval, a few round. The pathogen overwintered on the residual body with closed cysts, and released ascospores for the first infection in the following summer. After the disease was spread by wind and rain, the conidia formed in the diseased part, and the conidia were transmitted by wind and rain, and then infected again, and the ascospores were formed in autumn. Enter the overwintering place. The disease is serious in hot and humid weather and poor ventilation and light transmission, which can occur from May and June to September and October, but it is more serious in September and October.

Prevention and treatment:

At the initial stage of the onset of ①, spraying 2000 times of 25% Tylenol wettable powder, or 4000 times of 20% Tylenol emulsion, or 1500 times of 70% methyl topiramate wettable powder, once every 7 to 10 days, for 3 to 4 times, can achieve a good prevention and control effect. Foreign effective agents for the prevention and control of powdery mildew, such as azinamide, carbendazim and so on, can also be used.

② selected disease-resistant varieties and applied more phosphorus and potassium fertilizer to avoid rotation or close to other damaged flowers and plants of the pathogen, so as to avoid mutual infection and aggravate the disease.

Brown spot disease

Symptoms: the disease spot on the leaf is round or nearly round, 1Mel 5mm in diameter, initially brown, then the middle is grayish brown, the edge is dark green, there are inconspicuous wheel lines, when wet, the disease spot is dense with olive brown mildew on both sides.

Pathogens and characteristics: the pathogens are basidiomycetes subphylum, Cercospora, conidium undeveloped, conidiophores clustered, light green, rarely separated or branched, straight or wavy. The pathogen overwintered on the diseased fallen leaves with hyphae, and produced conidia in the following year, which were transmitted by airflow and infected the plant. The disease usually occurs in August and September, and if it is rainy and humid at this time, the disease is more serious.

Prevention and treatment:

Spray 0.5% Bordeaux solution before the onset of ①.

After the onset of ②, 50% carbendazim wettable powder 1000 times or 50% dichlorothalonium 1000 times or 70% chlorothalonil wettable powder can be sprayed.

The disabled body was removed by ③ and treated centrally.