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Reasons For Poor Herbicide Effectiveness
Source: | Author:pmo9a49c2 | Published time: 2021-11-05 | 785 Views | Share:

1. temperature

The high temperature is good for the herbicide to be absorbed by the weeds and the effect is good. But not the higher the temperature, the better. If the temperature is too high, the sprayed mist will evaporate quickly. Especially for some volatile herbicides and herbicides that are decomposed by light, it will reduce the herbicidal effect, such as 2.4-D, fluorine Le Ling, Heda Zhuang, dimethyl tetrachloride, etc., can also cause phytotoxicity by drifting to surrounding sensitive crops due to volatilization. When the temperature is too low, use Promethazine, the plants cannot degrade it in time, and it is prone to phytotoxicity. The correct application should be: high temperature season, sunny and windless before 11 am and after 4 pm; low temperature season should be between 10 am and 3 pm.


2. Air humidity

Generally speaking, high humidity helps the herbicide to be absorbed by weeds and has a good effect. The best time is when there is no dew on the leaves, no rain, and the air humidity is above 60%. If it is too dry in hot and dry season, do not apply the medicine. 


3. Soil moisture

The soil moisture is sufficient, and the crops and weeds grow vigorously, which is conducive to the decomposition of the pesticide by the crops and the absorption of the pesticide by the weeds and the transmission and transportation in the body, so as to achieve the best weeding effect, especially the soil treatment agent must have the soil moist condition to play Good efficacy. For example, the soil is dry, crops and weeds grow slowly, and crop tolerance is poor, and it is conducive to the formation of a thicker cuticle in the stems and leaves of weeds, which affects the absorption and conduction of herbicides, thereby reducing the efficacy of herbicides. At the same time, in order to adapt to the arid environment, most of the pores of weeds are closed, which affects the absorption of the medicine, and the root system is more developed, which increases the difficulty of control. Therefore, in dry weather, a high limit is recommended, and the amount of water sprayed should be increased when spraying. 


4. Precipitation

Rain falls shortly after application, and the liquid medicine is easily washed away, which affects the efficacy of the medicine.


5. Light

The herbicides such as fendifen and condimentum are all light-activated herbicides, which kill weeds only under the action of light. The photosynthesis inhibitors such as simazine, diuron, and promethazine also need to be in the light to inhibit the photosynthesis of weeds and exert the weeding effect. Trifluralin is volatile when applied to the surface of the soil, and is easily decomposed when exposed to light, so it needs to be mixed with the surface soil in time. 


6. Soil pH value 

When the pH value is between 5.5 and 7.5, most herbicides can work well. Soils that are too acidic and too alkaline will decompose some herbicides, thereby affecting their efficacy. For example, soil sealing herbicides are acidic. The effect of closed weed control in saline soil is poor or even ineffective. Another example is the rapid degradation of chlorsulfuron in acidic soils, which affects the efficacy of the drug, and slow degradation in alkaline soils, which is likely to cause phytotoxicity to sensitive crops.


7. Soil texture and organic matter content 

Soils with loose texture and low organic matter content have less adsorption capacity, and excessive leaching can cause damage to crop roots. Cohesive soil and soil with high organic matter content have strong adsorption capacity, so that the chemical solution cannot move in the soil solution to form a uniform chemical soil layer, which will cause "unsealable" phenomenon and affect the effect. Therefore, the dosage of the chemical should be appropriately increased or used Recommended upper limit. In high water and fertilizer fields with too high organic matter, soil treatment herbicides are generally not used.


8. Water quality

Refers to the hardness and pH of the water mixed during application. Hardness refers to the amount of Ca2+ and Mg2+ ions contained in 100 ml of water. Since the effective ingredients of some herbicides are easily complexed with these two ions to form salts and be fixed, the water with high hardness may reduce the efficacy of the herbicides. Pesticides with acidity and alkalinity mixed with water with higher alkalinity or higher acidity will affect the stability of the medicament and reduce the herbicidal effect.  


9. Wind speed 

Herbicides should be applied when there is no wind or breeze. When the herbicides are sprayed in strong wind, the droplets are prone to drift and harm the surrounding sensitive crops. Especially volatile herbicides should be used with special care. 


10. Grass age

The best control period for weeds is in the 2-3 leaf stage. If the weeds are too old and the resistance increases, the dosage must be increased appropriately. 


11. Application period

In winter wheat producing areas, the application time is divided into pre-winter application and post-holiday application. Herbicides must have a suitable temperature for their efficacy. Low-temperature application will lead to poor weeding effects. In severe cases, wheat poisoning will occur. It is recommended to use products with good low-temperature resistance for application before winter. It is recommended to spray the herbicide 40 days after the winter wheat is sowed with the masking water (first water) after the holiday. At this time, the wheat is at the 4-leaf or 4-leaf 1-heart stage, and it is more tolerant to the herbicide. It is safest to use herbicides after 4 leaves. In addition, when the wheat 4 leaves stage, most of the weeds are already out, and the grass age is relatively small, the wheat has no tillers, and there are not many leaves, which makes it easier to kill the weeds. The herbicide is most effective when used.


12. Secondary dilution

One of the important factors for herbicide efficacy is secondary dilution. First, add a small amount of water to prepare the mother liquor, then pour it into a sprayer with a certain amount of water, then add the amount of water to be added, and stir while adding, mix and dilute. To the required concentration. The secondary dilution is related to whether the medicinal solution is evenly dispersed in the medication equipment, and will eventually affect the weeding effect.


13. Application concentration 

Too much or too little application concentration will have an impact on the weeding effect. Therefore, the water distribution of herbicides should be scientific and should be carried out strictly in accordance with the instructions. Do not increase the dosage without authorization.


14. Chemical application equipment

The final weeding effect will vary depending on the equipment used for spraying. With the improvement of agricultural modernization, machine spraying has become more and more common, and the difference between it and manual spraying has become more and more obvious.

15. Differences in the spraying population 

The application of pesticides by people of different ages and genders will also affect the spraying effect. In addition, people's emotions will also indirectly affect the effect of spraying. 


16. Alternate medication 

Weed resistance is becoming more and more serious. It is easy to develop resistance to weeds using the same herbicide every year, and the weeding effect of alternating drugs will be better.  


17. Miao Qing

For diseased or weak seedlings, reduce the dosage or delay the application.  


18. Choose the right herbicide

There is no best, only the most suitable. A good herbicide is not necessarily the most suitable. The most suitable herbicide should be selected according to the local herbaceous phase, so as to achieve a good weeding effect.