As the peak season for vegetable production approaches, especially during summer when temperatures rise significantly, farmers across the country often encounter issues related to pesticide application. This can lead to phytotoxicity in vegetables, which is a serious concern for both crop health and yield. The causes of phytotoxicity are multifaceted. First, changes in climate and environmental conditions can increase the risk of chemical damage. Second, improper use of pesticides, such as incorrect dosage or wrong timing, contributes to the problem. Third, poor application techniques, like excessive spraying or incorrect methods, also play a role. Lastly, the lack of preventive measures makes it harder to control the spread of phytotoxic effects.
Common symptoms of herbicide-induced phytotoxicity vary depending on the type of vegetable and the specific herbicide used. For example, monocotyledonous plants exposed to certain herbicides may show growth inhibition, with stunted buds and meristems appearing within five days. Leaves may gradually turn purple or yellow and eventually wither around ten days later. In soybeans, pre-sowing treatment with acetochlor can cause leaf shrinkage, rough surfaces, shortened midribs, and heart-shaped or cup-shaped leaves, resulting in dwarfed plants and pale foliage. If sulfonylurea herbicides like chlorsulfuron-methyl are applied at the three-leaf stage, they may cause yellowing, leaf shrinkage, brown veins, and weakened stems that break easily. Although some branches may develop later, the plants tend to be late-maturing and produce lower yields.
Inappropriate application of glyphosate can lead to chlorosis, necrosis, and drying of the entire plant. Paraquat exposure in sweet corn causes new leaves to wilt and dry out completely. Eggplants and tomatoes affected by carbamoyl herbicides such as chlorfenapyr may exhibit cup-shaped leaves due to growth point inhibition.
To prevent and reduce phytotoxicity caused by herbicides, several practical measures should be taken. First, adjust herbicide application based on environmental conditions. Avoid applying herbicides when temperatures fall below 15°C or exceed 35°C. During high temperatures, droughts, or strong sunlight, it's best to avoid weeding herbicides. Optimal times for application are between 4 AM and 10 AM when temperatures range from 15°C to 30°C and the soil is moist. Herbicides are less effective in soils with low organic matter and high salinity. Conversely, soils rich in organic matter and low in salinity have strong herbicide adsorption capacity and are generally less prone to phytotoxicity.
Selecting the right herbicide and using it at the correct time is crucial. Choose herbicides that target weeds commonly found in local vegetable crops. Dilute them properly according to the active ingredient concentration. Mixing herbicides should be done scientifically, avoiding random or indiscriminate use. Also, pay attention to application timing—whether before sowing, before emergence, or after emergence—and ensure strict adherence to these stages.
If phytotoxicity is detected, quick action is essential. Using products like Huimanfeng active liquid fertilizer can help alleviate the damage. For instance, peppers can be sprayed with a 1:800 to 1:1000 dilution, while other vegetables can use a 1:500 dilution. Spraying 1:800 diluted Harvest No. 1, 0.05% 920 solution, or PBO regulators can also help detoxify and repair damaged cells. Increasing nitrogen fertilizers like urea or manure water can promote seedling growth and recovery. These steps, when applied promptly, can significantly reduce the impact of herbicide toxicity on vegetable crops.
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