Blight usually occurs from June to harvest, endangering the growth of Perilla.
At the beginning, small brown or black brown spots with different sizes and shapes appeared on the leaf surface, and then developed into large round or polygonal spots with a diameter of 0.2-2.5cm.
The disease spots are not obvious on purple leaves, but more obvious on green leaves. After drying, they often form cavities. In serious cases, the disease spots converge and the leaves fall.
When selecting seeds, we should select the disease-free plants.
Pay attention to the drainage of the soil to avoid over planting.
At the beginning of the onset, 80% wettable zinc 80O solution or 1:1:200 Bordeaux spray were used. Spray 2-3 times every 7 days. However, spraying should be stopped half a month before harvest to ensure that the medicine does not contain pesticides.
From June to August, when the weather is dry and the humidity is high, it is easy to appear.
Red spider adults are small, usually orange red, sometimes yellow. The red spider gathered on the back of the leaf and sucked the juice. At the beginning, the yellow and white spots appeared on the leaves, and then the large yellow and brown spots could be seen on the leaves.
When the spots expand, the whole leaf turns yellow and leaves fall off.
At the early stage of occurrence, 40% dimethoate emulsion 2000 times was used to spray kill. But it is required to stop spraying half a month before harvest to ensure that there is no residual poison on the medicinal materials.
From July to September, the larvae damage the growth of perilla, and the leaves will become hollow. The mature larvae pupate on the plants as thin silk cocoons.
Spray with 90% crystals of 1000 fold water.
