Causes of crop injury and its symptoms

Although the causes of phytotoxicity are complex, they can generally be summarized into three main categories: First, the misuse of pesticides or the presence of impurities in them; second, the use of degraded pesticides that contain harmful substances; and third, the lack of proper knowledge in pesticide application techniques, such as spraying at inappropriate crop growth stages, under unsuitable weather conditions, or using incorrect methods. The main symptoms of phytotoxicity include: (1) Spot type: This is characterized by the appearance of spots on leaves, stems, or fruit surfaces. Common types include brown spots, mottled spots, and net-like lesions. For example, improper use of butachlor in rice fields can cause irregular browning on rice leaves. Jinggangmycin may lead to yellow spots on watermelon leaves, while Bordeaux mixture can cause brown net-like spots on apple skin. (2) Yellowing type: This occurs when chlorophyll synthesis is disrupted, leading to leaf yellowing. Symptoms range from localized yellowing to complete plant yellowing. For instance, fenthion may cause yellowing on new shoots of watermelons, while simazine can cause yellowing starting from the leaf edges and spreading inward. Diuron may result in yellowish-green cotton seedlings. (3) Malformation type: This affects stems, leaves, and roots, causing deformities such as curled leaves, clumped growth, swollen roots, or malformed fruits. For example, dimethyltetrachlorobenzene may cause swelling at the base of wheat buds and young roots, while herbicidal ether can cause blister-like damage on cotton leaves. Tomato plants exposed to 2,4-D may develop hollow or misshapen fruits. (4) Withering type: This leads to rapid wilting and death of the entire plant, often due to improper herbicide use. Glyphosate injury on rice seedlings can cause yellowing and eventual death, while chlorotoluron may cause watermelon seedlings to wilt and die. (5) Growth inhibition type: This results in slow growth and reduced yield. Improper use of green mellon in rapeseed may lead to stunted growth and fewer branches, while paclobutrazol in paddy fields can delay heading if not applied correctly. (6) Sterility: This occurs when crops are exposed to harmful chemicals during their reproductive phase, leading to infertility. For example, rice shoot green can cause male sterility in rice, resulting in empty panicles and lower yields. (7) Shedding type: This is common in fruit trees and dicotyledonous plants, where leaves or flowers fall prematurely. Copper-based preparations may cause defoliation in peach trees, while methamidophos during flowering can lead to flower drop in pears. Ethephon misuse in hawthorns may cause both fruit and leaf shedding. (8) Poor fruit quality: This results in smaller, deformed, or low-quality fruits. Ethylene toxicity in watermelons can cause dark red, odorous melons, while copper-based sprays on tomatoes may lead to brown spots on the fruit surface. Grape damage from excessive growth regulators can cause loose clusters and shriveled fruit. What is the difference between phytotoxicity and disease? Phytotoxicity often shows irregular symptoms across the field, while physiological diseases tend to have uniform patterns. Spot-type phytotoxicity varies in size and shape, unlike fungal diseases, which usually have a central onset. Yellowing from phytotoxicity tends to occur rapidly in sunny conditions, whereas nutrient deficiency-related yellowing develops slowly and is consistent across the field. Virus-induced yellowing often appears mottled and systemic, with diseased and healthy plants mixed together. Deformities caused by phytotoxicity are usually localized, while virus diseases often show systemic symptoms like mottled leaves or wrinkled foliage. Wilt from phytotoxicity lacks a clear center and progresses slowly, whereas disease-induced wilting is often rapid and accompanied by root discoloration. To prevent phytotoxicity, it is essential to: (1) Conduct small-scale trials before large-area application to determine appropriate dosage, timing, and method. (2) Use pesticides strictly according to instructions, ensuring correct concentration, timing, and application technique. (3) Clean sprayers thoroughly, especially after using herbicides, to avoid cross-contamination. Plastic sprayers should be soaked in 5% lye, while iron ones should be treated with 1% ferrous sulfate solution. Nozzles and other parts must also be cleaned carefully. After applying pesticides, it’s important to monitor crops closely, especially after using herbicides or growth regulators. If phytotoxicity occurs, several remedial measures can be taken: (1) Fertilization: Applying additional nutrients can help reduce the impact of foliar damage. For example, urea and potassium dihydrogen phosphate can be used to treat wheat affected by chlorotoluron. (2) Irrigation and drainage: Proper watering can mitigate the effects of some herbicides. (3) Hormonal treatment: Spraying gibberellin after exposure to certain herbicides, such as 2,4-D butyl ester or dimethyltetrachlorobenzene, can help alleviate symptoms.

Card Recognition Time Attendance

8 inch touch screen recognition intelligent terminal,Touch Screen Intelligent Terminal,Fingerprint Identification Intelligent Terminal

Shenzhen Bio Technology Co., Ltd , https://www.huifantech.com