Physical injury and Prevention of Sijilan

Physical injury includes drug injury, fertilizer injury, sunburn, frostbite and acid rain erosion. The symptoms of these injuries are very similar to leaf spot disease and are often misjudged as diseases, and some are infected with leaf spot or toxin disease due to physical injury. if carefully observed, there are still many differences in their characteristics.

Take fertilizer damage as an example, the most common is the scorched tail caused by overweight phosphate fertilizer in winter. In the early stage, there is a yellow dot near the 1cm from the tail of the leaf, and there is a water immersion around the yellow spot, then the rhubarb spot, and finally the black focal tail. The reason is that the winter temperature is low, the metabolism is slow, and too much salt accumulates at the end of the leaf. This phenomenon will not happen in other seasons. Although the symptoms are at the end of the leaf, it is not like anthrax to spread intermittently. It is also different from the rotting root scorched tail, which is black and green and occurs in the old plant, while the fertilizer damage occurs in the new plant.

Another kind of fertilizer damage occurs below the bulb, resulting in hardening and necrosis of the root tip and blackening of the root tip. The reason is due to excessive fertilization or the use of incomplete mature organic fertilizer, or the neutralization of fertilizers and pesticides to produce inorganic salts. Most of the seasons occur when the weather is fine after the rain in spring and summer.

Most of the drug damage occurred in the new bud stage, the new bud just unearthed or the opening of the bud center accumulated too many pesticides, resulting in scorched black leaf sheath or leaf rash and wrinkle. Because the injury was at the base of the bud center, the inner and outer leaves showed unequal height drug spots when the plant was grown. The new bud stage is most likely to occur when the room temperature is above 30 ℃, especially copper agents (such as Quadrine, copper sulfate, copper mannapu, copper hydroxide, etc.) and summer oil. Therefore, during the high temperature period in spring and summer, it is safe to reduce the dose by 20% to 50%.

The most common season of sunburn occurs at the turn of spring and summer and the turn of autumn and winter, when the temperature varies and the black net is closed too early or too late, which often burns the turning point or tail of the leaf. For example, "Tianxiang" white claws are easy to scorch and black for this reason. For the sake of safety, it is better to let it grow in vain due to lack of sunshine than to affect its quality because of sunburn.

Four seasons orchid, autumn buds usually sprout in November, the coldest January and February are suitable for the opening period of the bud core, the accumulated dew is easy to frost and frostbite, the leaf back of Gaoyi plant is prone to black spots such as iron rust, and the leaves are scorched black and deciduous in serious cases. The symptoms of new bud frostbite are very similar to drug damage, and the scope is wider. Areas harmed by frost and snow in winter are not suitable for open-air cultivation, it is necessary to move indoors or set up double-layer film protection, single-layer film is easy to make water vapor condense into ice water, dripping to the leaf surface to cause greater damage.

The harm of acid rain in recent years is more serious, especially in metropolises and its suburbs, because the afternoon thunderstorm entrainment of sulfides in the air to form acid rain (PH4.O or so), dripping onto the leaves causing corrosive black spots, different sizes and evenly distributed, old plants and new leaves will be injured, the initial flooding-like spots turn yellow and black two days later, the black spots will not expand and the surrounding halo will not rise. Prevention and treatment: immediately watering after a short shower.

Physical injury, in addition to the above five more common, other such as water pH is too high, EC value is too high, limestone is too heavy, medium is too loose to cause root damage, air pollution, temperature difference is too large, lack of ultraviolet light will also cause poor leaf growth. As these injuries are often mistaken for diseases and insect pests, the exhaustion of all pesticides has no effect, but careful observation can also see the clues.

Note: the effect of ultraviolet rays is to promote phototropism, make leaves thicker and straighter, and increase disease resistance. If the film turns yellow or moss grows, it will hinder the entry of ultraviolet rays, plants can still carry out photosynthesis, but the thread art will degenerate and the leaf shape will be softer and saggy. On the contrary, too much sunshine or too long light exposure (more than 16 hours) will cause leaves to dwarf and yellowing, or even early aging without budding. (Liu Qingyong)