Disease prevention and control methods of Verbena

powdery mildew

symptom

It mainly harms leaves, but also infects petioles and stems. In the early stage, nearly circular white powdery spots appear on the leaf surface, which quickly expand and connect into pieces, forming large white powdery areas with unclear edges and covered with white powdery mildew. In severe cases, the leaves turn yellow and wither. Disease pattern: high air humidity. Higher temperatures are conducive to the occurrence of diseases.

measure

Pay attention to ventilation and light, avoid over-dense planting, and remove and burn early diseased leaves. In the early stage of the disease, spray 800-1000 times diluted 50% thiophanate-methyl, or 0.1-0.3 degrees Baume lime sulfur mixture, or 600-800 times diluted thiophanate-methyl once a week for 2-3 times.

Botrytis cinerea

symptom

When the petals are damaged, small water-soaked spots appear, which soon expand, turn brown and rot. The leaves are affected, with brown and soft spots first appearing on the edges and then spreading to the entire leaf. When the weather is humid, a gray mold layer will form, which will then turn brown and dry up. Disease pattern: The pathogen overwinters as sclerotia. It is easy to cause disease when the temperature is 20℃ and the humidity is high.

measure:

Increase the temperature of the environment, reduce humidity, and pay attention to ventilation and light. In the early stage of the disease, spray 600-800 times diluted Haoshengling or 800 times diluted thiophanate-methyl wettable powder. Once a week, three to four times in a row.

Stem rot

symptom

The base of the stem of the affected plants close to the soil surface is dark green at first, and then becomes brown and rots after expanding. When it is humid in the morning, white filaments can be seen on the lesions, and if the damage is severe, the diseased plants will fall over. The disease mostly occurs in rainy weather, excessive watering, and waterlogging in the soil.

measure

Strengthen management during the outbreak period, and water less or not at all when the air humidity is high to keep the soil in the pot moist. Apply less nitrogen fertilizer and more phosphorus and potassium fertilizer. Remove the diseased and old leaves whose lower parts are in contact with the soil in time. After the disease occurs, spray 500-700 times diluted 65% dichlorodiphenyltrichloroethane, or 600-800 times diluted thiamethoxam.