In production, wheat farmers basically know that herbicides can be used for soil closure. After the weeds are emerged, the stem and leaf treatment agent is applied. Currently, there are many kinds of medicaments for controlling wheat weeds, and it is necessary to have a certain understanding to select a herbicide suitable for local weeding.
However, according to the survey, in many places, when using herbicides, attention is not paid to the external environmental conditions, especially the temperature conditions at the time of application. Therefore, the occurrence of phytotoxicity accidents caused by neglecting the weather conditions during application often occurs. There is no undue loss.
Here are some of the herbicides used in the wheat area, which are closely related to the temperature conditions.
Experienced wheat farmers know that when purchasing herbicides for weeding in wheat fields, most of the instructions have been adapted to the temperature range. This must not be ignored, because these instructions are summarized from the production practice. In order to exert the effect of herbicides, not only the herbicidal effect is good in the suitable warm garden, but also the safety of wheat is good; while the temperature influence is neglected, it is easy to cause local or large-scale occurrence of the phytotoxicity. The following are some of the herbicides that are closely related to temperature when used.
Isoproturon
Most of the products currently available on the market are 50% isoproturon WP. In recent years, practice has shown that wheat is weeded in late November or mid-December. At this time, the temperature is low, and even low temperature of about 0 °C or below is used. After the young wheat seedlings grow young, most of the wheat seedlings will die, and the wheat leaves will be boiled with water, the leaves will become darker, the leaves will be drooping, and the symptoms will be dry and white. This is because the drug is a selective systemic herbicide, which is absorbed by the roots and then transported into the leaves with water in the duct to inhibit the photosynthesis of green plants, thereby exerting a herbicidal action. However, isoproturon can reduce the anti-freezing ability of wheat seedlings. After applying isoproturon, the wheat field encounters low-temperature frosty weather in a short period of time, which is commonly referred to as “frozen phytotoxicityâ€. The tip of the leaf is dry and the leaves are like boiled water. If frost occurs at night after application, as well as tender seedlings and accumulated paddy fields, the phytotoxicity will be more serious. The application of isoproteren in the wheat field where the low temperature and frost cause phytotoxicity, if the field wheat seedlings are less damaged, only the leaves appear yellow, no dead seedlings appear, and the wheat field can gradually return to normal growth, which has little effect on the yield. Foliar fertilizers such as potassium dihydrogen phosphate and humic acid are sprayed on the frozen wheat field, which is conducive to the recovery of wheat seedlings.
Isosulfuron
Isosulfuron is a stem and leaf treatment agent, which can prevent grass weeds and broadleaf weeds in wheat fields such as Mai Niang, Mai Mai, wild oats, wild geranium, leeks, and sorghum. The drug is absorbed by weed leaves, leaf sheaths, stems and roots, accumulates at the growth point, inhibits acetolactate synthase, and cannot synthesize branched-chain amino acids, thereby affecting protein synthesis, affecting weed cell division, causing weeds to stop growing and yellowing. Then die. This medicine should not be applied before severe weather such as low temperature frost (minimum temperature below 2 °C). It should not be applied in wheat fields suffering from phlegm, freezing, salt, disease and malnutrition. It should not be flooded within 2 days before and after application. In order to avoid phytotoxicity. Cold weather that cannot be reached within 2 days after application, the minimum temperature is below 0 °C to stop the medication, so as not to cause phytotoxicity to wheat. The sulfonamide has good mixing performance and can be combined with Maixi 58g/L of difluoro. The pyrazolam suspension, flupiroxine, benzenesulfonic acid, bromoxynil, xylene tetrachloride, and isoproturon are mixed to expand the herbicidal spectrum, but cannot be mixed with oxazin.
Bromobenzonitrile
Bromoxynonitrile is a contact-selective post-stem and leaf-leaf treatment agent. The drug is mainly absorbed by the leaves and conducts very limited conduction in plants. The plant tissue is rapidly necrotic by inhibiting various processes of photosynthesis. Generally, the weed leaves are chlorotic and necrotic spots appear within 24 hours after application, and the leaves are accelerated under conditions of high temperature and strong light. It is advisable to apply the medicine when the sunlight is strong and the temperature is high, which is beneficial to the effect of the medicine and accelerate the death of weeds. Wheat is more resistant to this drug, and normal application will not cause phytotoxicity, but if it is not applied properly, it will cause yellowing of wheat leaves. In order to prevent the occurrence of phytotoxicity, the drug should be diluted twice, and the amount of water should be increased to avoid the phytotoxicity caused by excessive application concentration. Generally, 40-50 kg of water per acre is sprayed evenly. In the case of low or high temperature after application of bromoxynil, the herbicidal effect may be reduced and the safety of the crop is also reduced. Generally, after bromoxynil is applied, the detoxification process in the crop is slow and easy to cause phytotoxicity, especially in frosty weather, causing yellowing of the leaves of the wheat seedlings. After 30 days of spraying 40% dimethyl bromide emulsifiable concentrate on the wheat field, there was a low temperature frost weather, which may be the main cause of yellowing of wheat leaves. Bromoxynil is a contact herbicide. The larger wheat seedlings generally do not die after the leaves are damaged. However, the weak seedlings with severe damage and severe damage to the leaves may cause death of the whole plant. After the temperature rises, the affected wheat seedlings can generally resume growth after about half a month. If the wheat is in the tillering stage, there is no jointing, and after a low temperature frost weather about 3 days after the application, the wheat leaves will appear yellow. In severe cases, the wheat seedlings will cause the heart leaves to die, and the weak seedlings are seriously damaged. Injury, there may be death of the whole plant. After the temperature rises, the affected wheat seedlings can generally resume growth after 15-20 days, and the early application of jointing ear fertilizers will accelerate the growth of the wheat seedlings.
Acetochlor
Acetochlor is a selective pre-emergence herbicide, the drug can be absorbed by plant sprouts, monocotyledons are absorbed by the bud sheath, and dicotyledons are absorbed and transmitted through hypocotyls, which interfere with nucleic acid metabolism and protein synthesis in plants, so that sprouts The young roots stop growing. If the field moisture is suitable, the weed shoots are killed without being excavated; if the soil moisture is small, the weeds will increase with the soil moisture and the weeds will take effect after absorbing the drug. The symptoms of grass weed poisoning are heart curl atrophy, Other leaves shrink, and the whole plant is dead. After the application of thifensulfuron and acetochlor in the rain, the humidity in the field is too large or accumulated for a long time, all of which will cause phytotoxicity to wheat, which will lead to no emergence of seedlings. The safety of acetochlor to wheat is relatively poor. After the application of the grass in the wheat field, the soil moisture is too dry, and it is easy to cause obvious phytotoxicity to the emergence of wheat and seedling growth. If there is water in the field, the wheat seedlings in the water will be more seriously damaged. The symptoms of phytotoxicity of wheat were affected by germ growth and emergence, and the emergence rate decreased. The first leaf was distorted, deformed and plant dwarfed. The phytotoxicity is aggravated with the increase of the application amount of the herbaceous plant. When the same amount is applied, the phytotoxicity is aggravated with the increase of the soil water content. Use 20% sulfene per acre. Acacia is 110 grams of wettable powder, and the dosage is slightly larger, but in the case of normal application, it generally does not cause phytotoxicity to wheat, resulting in no emergence. According to reports, if there is moderate rain in the local area 2 days after application, there will be continuous rainy weather. Although there is no water in the field, the soil moisture is too high and the wheat is susceptible to sulfene. Acetochlor is phytotoxic, resulting in no emergence or suppression of wheat seedling growth.
Cholesterol
The herbicide is a commonly used stem and leaf treatment agent for wheat, and is suitable for controlling grass weeds such as Mai Niang, Japanese Mai Niang, Wild Oats, etc. The medicine is divided into two categories: one is the common evil grass. Ling, mainly used for weeding of broad-leaved crops such as soybeans and peanuts, this kind of oxazocilin herbicide has been clearly not used for weeding in wheat fields. Another type of oxazolamide is a safener-added preparation. For example, Bayer-produced hummers are available on the market. They can be used to control grassy weeds in wheat fields, maidens, wild oats, etc. Generally, the use of 6.9% thioxazole grass emulsifiable concentrate per acre is 50-60 ml. When the grass age is large, the dosage can be appropriately increased, but the amount of ar in the hand should not exceed 150 ml, otherwise it may cause phytotoxicity. When using the herbicide Liu, if the cold current is encountered within 3-4 days after application, the wheat seedlings may be yellow, the leaf tips are white, and the wheat seedlings may cause dead seedlings when they are small. Therefore, it is best to choose to apply the medicine on a better sunny day to ensure safety and not to be used after wheat jointing.
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