What symptom does tomato powdery mildew have? What are the key points of prevention and control techniques?

Tomato is a kind of nutritious vegetable, which is planted everywhere. In the process of tomato planting, diseases will occur due to some reasons or climatic conditions, such as powdery mildew. What are the symptoms of tomato powdery mildew? What are the key points of prevention and control techniques?

What are the symptoms of tomato powdery mildew?

Leaf disease: in the early stage of the disease, you can see a layer of white mycelium growing on the back of the leaf. At this time, the leaf itself has no other obvious changes. With the development of the disease, the leaf begins to curl upward, like a spoon. At the same time, dark spots, large and small, are produced on the leaf, and then the disease spot gradually expands, and a layer of white powder is produced on the back of the leaf, that is, the conidiophores and conidia of the pathogen. Disease spots generally exist alone, and when they are serious, multiple disease spots are connected together, covering the whole leaf. In the later stage of the disease, the color of the disease spot changed, showing reddish brown, and the edge of the leaf atrophied and died.

Flower bud, flower infection: after the flower is infected, the petals lose their previous color and become pink, and compared with normal buds, the infected buds do not open normally.

Fruit infection: after the fruit is infected, the shape changes, showing a long and thin shape, and can not normally expand, the whole fruit looks dry. If the green fruit is damaged, it will not expand, and the fruit will lose its luster, like a stiff fruit; after the colored fruit is damaged, the coloring speed will slow down, and the fruit surface will be covered with white powder, which will affect the fruit quality and gradually lose its commercial value.

2. Incidence regularity of tomato powdery mildew.

In the north of China, the pathogen overwinters mainly as asexual spores on winter tomatoes, and it can also overwinter on the ground with the remains of the disease. when the conditions are suitable, the ascospores scattered from the closed cysts spread with the airflow, and then produce conidia in the diseased part, and the mature conidia fall behind and re-infect through the air flow. In the perennial tomato planting area in the south, the pathogen had no obvious overwintering phenomenon, and the conidia were produced continuously. The optimum temperature for conidia germination of tomato was 20: 25 ℃, and that of powdery mildew in Tatar was 15: 30 ℃. Open fields mostly occur in June-July or September-October, while greenhouses or plastic greenhouses are more common in March-June or October-November.

Third, what are the key points of prevention and control of tomato powdery mildew?

1. Breeding varieties resistant to powdery mildew and strengthening the management of temperature and humidity in greenhouse. Remove the disease and residue in time after harvest to reduce the source of overwintering bacteria. In the early stage of the disease, the shed can choose the dust method or smoke method, spray more than 10% 100 dust agents in the evening, 1 kg per mu each time, or apply 45% chlorothalonil smoke remover, 250 grams per mu each time, and light it with dark fire for one night.

2. Open field or greenhouse can choose 15% triadimefon (triadimefon) wettable powder 500x, 40% Fuxing EC 100008000x, 10% high water soluble granules 1500 times, 30% Teflin wettable powder 1500002000 times, 50% sulfur suspension 20000x. Or 50% triadimefon EC 500 times 600 times, 2% Wuyisin water agent or 2% agricultural anti-120 water agents 150 times, 25% enemy emulsifiable concentrate 3000 times, 15% triadimefon (triadimefon) wettable powder 2000 times, 25% chlorpromazine demulsifiable oil 4000 times, interval 7~15d1, continuous prevention and treatment for 2 times for 3 times.