The use of pesticides in fruit trees can both prevent and treat diseases and pests, promote the growth and development of fruit trees, and increase fruit yield and quality. However, because pesticides directly or indirectly act on various parts of the fruit tree, they will also have a certain impact on the fruit tree. Sometimes it will produce phytotoxicity, light leaves, flowers, fruit spots or scorch, heavy leaves, fallen flowers, fruit drop, Even dead branches die. The existence of phytotoxicity threatens the development of fruit production to a certain extent and should arouse our attention. Causes and remedial measures of the injury caused by fruit trees are briefly described.
First, the causes of injury
1. The dosage form of the medicine is not correct: the relationship between the physical and chemical properties of the medicine and the fruit tree is greatest. Under normal circumstances, inorganic agents with high water solubility and low molecular weight are most likely to produce phytotoxicity, such as copper and sulfur. Water-soluble agents are relatively safe and microbial agents are relatively safe for fruit trees. Different formulations of pesticides have different levels of harm caused by pesticides. Oil agents and emulsifiers are more likely to produce phytotoxicity, followed by WP, and milk powder and granules are relatively safe.
2. Fruit trees are sensitive to chemicals: Fruit trees such as peaches, apricots, and plums are sensitive to Bordeaux mixture during the growing season. No matter what kind of formula is used, it is extremely prone to phytotoxicity. When using 45% dexamethasone, pear and apple trees are susceptible to phytotoxicity when the dilution ratio of the liquid is less than 1000 times. Taoyuan, apricot, and cherry orchard use 40% atrazine for weeding, 300 ml per mu, there will be phytotoxicity, light yellow leaves, heavy leaves a lot.
3. Improper application of pharmaceuticals: The drug concentration is too high, the drug dissolves poorly, mixing is unreasonable, the spraying period is improper, etc., all of which are prone to phytotoxicity. If the Bordeaux mixture is mixed with lime sulfur or trehalose, or if the use interval is less than 20 days, it will produce phytotoxicity. Concentration-additive effects after compounding are more likely to occur, and concentrations should be appropriately reduced.
4. Inappropriate environmental conditions: The environmental conditions are most affected by temperature, humidity, and light. High temperature and strong light are prone to phytotoxicity, because the high temperature can enhance the chemical activity and metabolism of the drug, which is conducive to intrusion of the drug solution into the plant tissue and can easily cause phytotoxicity. For example, lime sulfur, the higher the temperature, the better the effect, but the occurrence of phytotoxicity The greater the possibility, but there are exceptions, such as oyster egg ester, in the low temperature and humidity conditions, apples, pears, some species susceptible to phytotoxicity.
When the humidity is too high, the application of some agents is also easy to produce phytotoxicity. If the Bordeaux mixture is sprayed, if the liquid does not dry, it will be in contact with rain, or the leaves will be sprayed when the dew is not dry, which will cause a sudden increase in the content of soluble copper on the leaf surface, which can easily cause leaf burns; When the wind is relatively large, the content of soluble copper on the leaf surface will also increase, causing the leaves to scorch and "wind and rain damage." Spraying herbicides in windy weather is prone to “driftingâ€.
Second, drug injury symptoms:
According to the speed of the occurrence of the injury and the apparent degree of symptoms, it is generally 3 kinds of acute injury, chronic injury and residual injury.
1. Acute injury: It means that symptoms of phytotoxicity appear soon after spraying (in hours or days). It is characterized by rapid development, obvious symptoms and visible to the naked eye. The general appearance is the appearance of spots on the blade, burning, perforation or chlorosis, yellowing, deformity, thickening, leaf curling and even withering, shedding and other symptoms; fruit on the spots, deformities, smaller, falling fruit and other symptoms; flower performance scorch, Flowering, discoloration, rot, buds and other symptoms; plant growth retardation, dwarfing, or even plant death.
2. Chronic phytotoxicity: refers to the injury that does not occur soon after treatment. Its characteristics are slow, some symptoms are not obvious, it is not easy to judge in a short time. In many cases, the growth performance is slow over a long period of time, and the flowering results are delayed due to poor development, fruit drop is increased, the yield is reduced, and the quality is deteriorated.
3. Residual phytotoxicity: When the fruit trees are sprayed, more than half of the pesticides will fall on the ground, and the pesticides in the soil or soil will remain in the soil. Some of these pesticides are decomposed slowly and accumulate to a certain degree in the soil, which will affect the growth of fruit trees. The symptoms are similar to chronic phytotoxicity.
Third, prevention methods:
If you understand the properties of the pesticide, the characteristics of the fruit tree, master the medication environment at the time and the correct application method, when using pesticides, you should strictly abide by the "Pesticide Safety Use Standards" and use it in accordance with the operating procedures. The principles of prevention must be followed. Pay attention to the following three points.
1. Test method: Although various medicines have instructions for use, they are more general or lack of representativeness. Because pesticides are often affected by many other factors, they should be used for small area tests. After 4-7 days, it can be seen whether there is any injury.
2, low-concentration water-washing control method: In the effective range of concentrations of pesticides to reduce the concentration of the liquid than the concentration should be reduced by 10-20%, increase the amount of spray, the tree under the tree, in and out, the leaves are Both sides are washed away, and it is better to avoid phytotoxicity and improve control. This method is particularly suitable for orchards that have developed resistance and have a high density of insect populations. The water flow control is applicable to pests such as leafhoppers and is not suitable for controlling diseases.
3. Scientific use: To avoid phytotoxicity of fruit trees, it should be based on the sensitivity of fruit trees to pesticides and the resistance of control subjects, the selection of pesticides on the road for comprehensive pesticide properties, the strict application of concentration and the time of drug use, and rational scientific drug use, especially Mixed pesticides must be mixed according to regulations.
Fourth, remedial measures:
The occurrence of phytotoxicity due to improper use of pesticides should be based on the specific cause of the phytotoxicity and the degree of harm, and actively take remedial measures to minimize the extent of phytotoxicity.
1. Water spray: If it is found early, sprinkle the water immediately to wash the affected plants to dilute and wash out the pesticides that adhere to the foliage and branches, and reduce the pesticide content in the tree body. The earlier and more timely the effect of this measure, the better.
2. Spraying and neutralizing: If the leaves are damaged by phytotoxicity, you can use the fulvic acid fertilizer Jiamei Jinli 1000 times for foliar spray; or the Jiamei 800-1000 times liquid for irrigation, after 3-5 days the leaves will gradually turn green. If it is caused by the copper sulfate ion in Bordeaux, it can spray 0.5-1% lime water solution to eliminate the phytotoxicity; if it is caused by lime sulfur, it will be sprayed with 400-500 times more rice vinegar solution on the basis of phytotoxicity. , can reduce the harm of medicine; if misuse or excessive use of organic phosphorus, pyrethroids, amino methyl esters and other pesticides caused by phytotoxicity, spray 0.5-1% of lime water, detergent powder, soapy water, wash clean water, etc. In particular, spraying ammonium bicarbonate alkaline fertilizer solution is better, not only has detoxification effect, but also can play a role in promoting growth and development outside the root.
3. Timely top-dressing: After fruit trees are damaged by phytotoxicity, their growth is hindered and they grow weaker. We must top-dress fertilizers in time to prompt the affected fruit trees to resume growth as soon as possible. If the phytotoxicity is caused by an acidic pesticide, some vegetation ash and quicklime can be applied. For the pesticide harm caused by alkaline pesticides, acid fertilizer such as ammonium sulfate can be applied. No matter what kind of phytotoxicity, spraying 800-1000 times of Jiameinao Platinum on the foliar surface, or spraying with 1000 times liquid Jiamei Jinli, spraying once every 5-8 days, spraying 2-3 times, can reduce the drug harm.
4, injection of clean water: in the prevention and treatment of Tianniu, gizil, wood moth and other pests dry, due to excessive drug concentration caused by phytotoxicity, immediately from the trunk hole on the worm to the tree into a lot of water, and Make it flow outward to dilute the pesticide. If it is an acid pesticide, add appropriate amount of quicklime in the water injection solution to accelerate the decomposition of the pesticide.
5, cultivating loose soil: After fruit trees are damaged, timely cultivating loose soil (depth 10-15 cm) on the garden, and artificial cultivation of roots, appropriate application of phosphorus, potassium, calcium fertilizer Fei Jiamei profit or within the potassium Germany, in order to improve the permeability of the soil, promote the development of the root system and enhance the ability of the fruit tree to restore itself.
6. Proper pruning: After the fruit trees are damaged by phytotoxicity, pruning should be carried out in an appropriate amount in time, and the dead branches should be cut off and the dead leaves should be removed to prevent the dead parts from spreading or being infected by pathogens to cause diseases.
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