Correct pesticide application methods for landscape plants
In the prevention of plant disease and insect pests of landscape plants, various phytotoxicity will be caused by many factors, which will cause pollution and injury on plant tissues or organs, such as flower, blade and stalk as well as will cause fallen leaves, fallen flowers and fallen fruit under less serious conditions and even lead to plant death under serious condition.
Generally speaking, phytotoxicity can be divided into acute phytotoxicity and chronic phytotoxicity. The former refers to that plants will have abnormal form after 12h-more than 10 days of drug delivery. For example, it will lead to spot, etiolation, withered of leaves and fruits as well as wrinkled leaves, fallen leaves, fallen fruit and so on. The latter refers to the phytotoxicity symptoms that will occur long time after spraying the drugs. For example, the photosynthesis will decrease, the maturation stage will delay, plants will become dwarf and deformed, there will be color difference and so on. Therefore, regarding those landscape plants that are sensitive to pesticide, it is especially important to correctly choose pesticide and application method for preventing plant disease and insect pests.
According to the application range and application method of pesticide, some experiments are needed before using the pesticide, in which it can spray the pesticide by mist spray, powder spray, smearing the leaves, smearing the stems, root irrigation and so on. After a period of time (about 7 days), observe whether the phtotoxicity occurs or not and compare it with the plants that have not been sprayed with pesticides. This step is especially necessary before using a new type of pesticide.
b. Avoid using pesticide in flower sensitive period
Flowers will have different suffertibility to pesticide in different growth period. Generally speaking, the mature organizations will have strong resistance to pesticides, while the young and juicy organizations will be sensitive to pesticides. Therefore, we should spray pesticides according to different organizations. In addition, as most of the flowers will be sensitive to pesticides in the flower season, we should use pesticide carefully so as to avoid excessive drug using on some parts of flowers. Besides, the thickness of cloud point is required to be moderate in mist spray and the spray nozzle should be kept a certain distance from the flowers. Therefore, according to different pesticide property, different application methods should be used.
c. Ensure goof quality of technical material and water
Make sure that the technical liquor is clear and transparent as well as no floccule and no sediment will exist in the liquor. Besides, after adding in the water, make sure that it can disperse automatically and no oil slick will appear on the water surface. No cracking is allowed in the powder pesticide, besides, the powder particle thickness should be kept moderate; make sure that the wettable powder technical can evenly disperse after adding in the water. Use clean soft water instead of pond water and pit water that contain impurity as well as hard water that contain excessive calcium and magnesium ions in diluting the pesticides.
d. Properly control pesticide concentration
As pesticide will all have a safe concentration range when it is used on different flowers, it will cause pytotoxicity on flowers once we exceed this range. Therefore, before making up a prescription, we should accurately calculate and measure strictly. Small area of pharmacodynamic test is needed before using a new type of pesticide so as to confirm the safe use concentration. The pesticide should be prepared and used at the same time and should not be replaced for too long, otherwise, sediment will generate or the effective components will dissolve. Properly control the drug using frequency, as the overfrequency of drug using will be easy to cause phytotoxicity. The application frequency of one kind of pesticide will depend on pest damage frequency and duration of pesticide, which should be mastered flexibly according to the right time and proper circumstances.
e. Pay attention to the mixing taboo of pesticide
Although there will be a lot of advantages by mixing the pesticides, we should also note that some pesticides will react after mixing and will increase toxicity. For example, by mixing organophosphorus pesticide with alkaline pesticide, EC agent with some water soluble agentia, Bordeaux mixture with lime sulphur and so on, it will not only reduce pesticide effect, but also will induce phytotoxicity.
f. Pay attention to the weather condition when spraying pesticide
Most of the pesticides will be easy to cause phytotoxicity when they are sprayed under high temperature.
Mixture, rosin mixture and other pesticide varieties that have high volatility are inhibited using when the air temperature is more than 35 degrees Celsius, or it will cause phytotoxicity. Besides, alkaline pesticides will also be easy to cause phytotoxicity when they are sprayed under high air humidity.
g. Some remedial measures
Below are some detoxication measures that can be taken after the plant phytotoxicity caused by using pesticides.
a. Spray potassium permanganate solution
Potassium permanganate is a kind of strong oxidant, which will have oxidation decomposition effect on many chemical substances. Therefore, by spraying 6000 times of potassium permanganate solution, it can effectively alleviate phytotoxicity.
b. Wash with clear water
If the phytotoxicity is caused by the excessive application concentration, we can fill the clear water in the sprayer and repeatedly spray the water on the leaves so as to flush away the residue pesticide on the leaf surface.
c. Inhibit using the same kind of pesticide
Try to use the pesticide as little as possible before the phytotoxicity has been completely relieved. Especially stop using the same kind of pesticide so as to avoid aggravating phytotoxicity.
d. Fertilize and water in time
After the phytotoxicity occurs, some quick-acting chemical fertilizer should be used combining with watering as well as intertillage is needed, thus plants will return to normal growth and development. Meanwhile, 0.3-0.5 percent of urea and 0.2-0.3 percent of buffer stock solution can be sprayed on the blade surface so as to improve nutritional status and increase root system absorbing ability. Besides, spray the back of leaves evenly at 18-25 degrees Celsius before 10 a.m. and after 16 p.m.