Lagerstroemia indica leaf blight

There are several situations for your reference: nitrogen deficiency: thin plants, slender and hard branches and small leaves. The color of leaves ranges from old leaves to new leaves, from strong green to light green, to reddish purple, until they wither and fall off. In severe cases, the whole plant loses its green color.

Prevention and control methods: increase the application of decomposed human manure, cake manure, manure or fertilizers such as ammonium sulfate, urea and ammonium nitrate. ?

Phosphorus deficiency: the leaves turn from dark green to copper, and the veins (especially petioles) are yellow and purple. It is difficult to form flower buds, and the flowers are small, few and light, which leads to poor fruit development and even premature withering and falling off. ?

Prevention and control methods: increase the application of bone meal, fish meal, poultry manure or calcium superphosphate, ammonium phosphate and potassium phosphate (phosphorus-potassium compound fertilizer), and generally use 0. 10% aqueous solution as root topdressing. ?

Potassium deficiency: the plants are short, the stems are soft and prone to lodging. The leaves often shrink, and the old leaves appear dark brown spots from the tip along the edge of the leaves, and the leaves turn yellow around, while the middle and leaves are still green. ?

Control methods: plant ash, 1% ~ 2% aqueous solution of potassium chloride (bulbs and tubers are not allowed) and 0.30% ~ 0.50% aqueous solution of potassium nitrate are used as topdressing outside the roots, and inorganic fertilizers such as potassium phosphate can also be used. ?

Calcium deficiency: young leaves are green and shriveled, with white stripes on the leaf margin, flowers are blocked, and new leaves are difficult to unfold or morbidly twisted. ?

Prevention and control methods: Before sowing or potting, apply a proper amount of calcium chloride in the soil to increase calcium disinfection (acid flowers are prohibited), and calcium nitrate can also be used as topdressing. ?

Magnesium deficiency: plants do not grow vigorously. Old leaves gradually turn green and white from bottom to top from the edge to the center, and various spots appear on the veins, and finally the whole leaf turns yellow. ?

Control method: continuously spray 0.20% ~ 0.40% magnesium sulfate solution for 3-4 times with an interval of 7- 10 day. Magnesium sulfate 5 ~ 10 kg per mu is used in the soil with serious magnesium deficiency, which is mixed with base fertilizer and applied to the soil in autumn or winter. ?

Sulfur deficiency: young leaves turn yellow from vein, and finally the whole leaves turn yellow, and the root system develops abnormally. ?

Iron deficiency: young leaves turn yellow to old leaves. ?

The prevention method of sulfur deficiency and iron deficiency can be sprayed with 0.30% ferrous sulfate aqueous solution for three times, with an interval of 65438 0 weeks each time, and the fog points should be fine and uniform when spraying. At the same time, 0.20% urea-iron aqueous solution can be used for root topdressing.