1. corn closed herbicide
corn closed herbicide mainly refers to the soil spraying treatment before sowing (or before transplanting) or before emergence of crops after sowing, which can kill weeds that have not emerged. Such herbicides in corn fields include acetochlor of amide, metolachlor, triazene, etc., and can prevent and kill many annual gramineous weeds and some small-grained broad-leaved weeds in the field.
2. Herbicide after maize seedling
The spraying time of herbicide after maize seedling is 2-5 leaves, when maize has high resistance and is not prone to phytotoxicity. Spraying can be carried out in the whole field before the 5th leaf and after the 6th leaf. It is necessary to lower the nozzle and spray around the corn seeds to prevent the drug from causing phytotoxicity when the liquid medicine is poured into the heart.
Due to drought and low temperature, corn grows slowly and weeds emerge irregularly in the northern spring corn field. When the weeds come out in full bloom, the corn has exceeded the 5-leaf stage. Some pesticides have poor efficacy, and it is easy to cause phytotoxicity if nicosulfuron is used again; It is easy to cause phytotoxicity if applied too early or too late.
if there is no pesticide application or the soil sealing effect is not good at this period, you can choose to use post-emergence herbicides to spray the stems and leaves of weeds that have emerged, and the control effect is still good.
In addition, we should know that the herbicide before seedling was put on the market early, and the herbicide after seedling didn't appear until several years after popularization.
3. Pre-emergence herbicide:
The main ingredients are "acetochlor and atrazine (atrazine)", and there are also products compounded with atrazine by alachlor, butachlor and ipratropium.
advantages: the soil is closed, and there is basically no phytotoxicity to corn.
Disadvantages: It is greatly influenced by the climate, especially in the case of drought, which often affects the weeding effect. In particular, the wheat harvested by machine is too high, the straw coverage rate is high, and the amount of liquid medicine used by farmers is insufficient, which directly affects the effect.
4. Post-emergence herbicide:
The main components are four kinds of nicosulfuron, mesotrione, oxadiazon and oxadiazon (domestic patented products), as well as these four kinds of mixed atrazine products and ternary compound products (all are the marketing methods of products sold by manufacturers, but the main weeding effects are nicosulfuron, mesotrione, oxadiazon and oxadiazole.
It is worth paying special attention to that nicosulfuron is easy to cause phytotoxicity to corn seedlings, even if some manufacturers introduce so-called safeners, they should not be trusted.
Advantages: Compared with pre-emergence herbicides, it uses less water and is less affected by climate.
Disadvantages: Improper use is easy to cause phytotoxicity (especially the first two are easy to cause phytotoxicity, while the latter two are relatively safe but costly).
5. Precautions for the use of corn herbicide
(1) Spray at a constant dose according to the prescribed dose, and do not increase the dosage at will.
(2) adopt the "secondary dilution method", prepare the mother liquor first, and then spray the water evenly.
(3) Generally, the suitable period of herbicide application after maize seedling should be after 2 visible leaves and before 5 visible leaves. If the drug is used at the stage of 5
~7 leaves, it should be used between rows of corn to avoid spraying the liquid medicine into the heart leaves.
(4) Some post-emergence herbicides are sensitive to sweet corn, seed fields and inbred lines, so don't use them. It should be used in strict accordance with the label instructions of herbicides, and I can also be used with Anbijie to prevent phytotoxicity.
(5) Strictly control the application period. Soil sealing treatment should be carried out within 3 days after corn sowing; The treatment of stems and leaves after seedling should be in the 3-5 leaf stage of maize, and the effect of early application is poor (annual weeds are unearthed irregularly)
(6) After soil sealing treatment, people and animals are not allowed to enter the ground for one week, so as not to damage the drug film and reduce the control effect.
(7) Corn treated with organophosphorus pesticides is sensitive to herbicides after seedling. The interval between the two drugs is at least 7 days.
(8) When using a motorized sprayer, the dosage shall not be increased without authorization, and repeated spraying is prohibited.
(9) Pay attention to cleaning the sprayer sprayed with organophosphorus pesticides before using herbicides.