As the peak season for vegetable production arrives, especially during summer when temperatures soar, farmers across the country often encounter issues related to pesticide application. This can lead to phytotoxicity in vegetables, which is a serious concern for crop health and yield. The causes of such damage are multifaceted. First, extreme weather conditions and environmental changes can trigger herbicide-related harm. Second, improper use of pesticides—such as incorrect dosage or selection—can result in toxicity. Third, flawed application techniques, including excessive amounts, contribute to the problem. Lastly, a lack of preventive measures makes it harder to control and manage phytotoxicity effectively.
Common symptoms of phytotoxicity vary depending on the type of vegetable and the herbicide used. For instance, monocotyledonous plants may show signs of growth inhibition after exposure to herbicides like glyphosate. Symptoms typically appear within 5 days, with buds and meristems showing abnormalities. After about 10 days, heart leaves and other foliage may turn purple or yellow, eventually leading to withering. In soybeans, pre-sowing application of acetochlor followed by cold and rainy weather can cause leaf shrinkage, rough surfaces, shortened midribs, and deformed leaves that appear heart-shaped or cup-shaped. Plants become stunted and pale. When sulfonylurea herbicides like chlorsulfuron-methyl are applied at the three-leaf stage, they can cause yellowing, leaf shrinking, brown veins, and weak stems that easily break. Although some branches may develop later, the plants tend to mature late, resulting in lower yields.
Improper application of glyphosate can lead to whole-plant chlorosis, necrosis, and drying. Sweet corn exposed to paraquat shows wilting and drying of new leaves. Eggplants and tomatoes affected by carbamoyl herbicides like chlorfenapyr exhibit cup-shaped leaves due to growth point inhibition.
To prevent and reduce herbicide-induced phytotoxicity, several technical measures should be implemented. First, adjust herbicide application based on environmental conditions. Avoid using herbicides when temperatures are below 15°C or above 35°C. During high heat, drought, or strong sunlight, weeding should be avoided. Optimal times for application are between 4:00 AM and 10:00 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, reducing the risk of phytotoxicity.
Second, choose the right herbicides and apply them correctly. Select products suitable for local weed types and vegetable crops. Dilute according to the active ingredient concentration. Mix herbicides scientifically and avoid random or indiscriminate use. Also, pay attention to timing—application before sowing, before emergence, and after emergence should be strictly distinguished.
Lastly, if phytotoxicity occurs, take immediate action. For example, Huimanfeng active liquid fertilizer can help alleviate symptoms. Pepper can be sprayed with a 1:800 to 1:1000 dilution, while other vegetables may benefit from a 1:500 dilution. Solutions like Harvest No. 1 at 1:800, 0.05% 920 solution, or PBO regulators can also be used to detoxify and repair damaged cells. Increasing urea or manure-based fertilizers can help strengthen seedlings and improve recovery. These steps can significantly reduce the impact of herbicide damage and support healthier crop development.
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