What are the common types of crop phytotoxicity

Pesticides play a very important role in agricultural production, but at the same time they also bring more or less adverse effects to crops. If such adverse effects worsen and cause abnormal reactions in crops, resulting in reduced yield and declining quality, this is phytotoxicity. Phytotoxicity varies in severity and in how quickly it appears. Based on the symptoms, it can be summarized into the following types:

Spots

This type of phytotoxicity mainly appears on leaves, including yellow spots, brown spots, and scorched spots. For example, butachlor applied in the early stage of paddy rice in the main field causes brown spots, and high concentrations of mancozeb can cause scorched spots on the edges of rice leaves. Sometimes spots also appear on stems, branches, and fruits. For example, when mancozeb is applied to young pears, spots on the fruit surface are likely to appear.

Yellowing

The cause of yellowing is that the pesticide hinders the synthesis of chlorophyll, or blocks the photosynthesis of chlorophyll, or destroys chlorophyll. For example, applying fenvalerate to watermelon causes new shoots to turn yellow; tribenuron-methyl used in wheat fields drifts onto other crops and causes yellowing, and so on.

Deformity

This type of phytotoxicity can occur in all organs of the plant. Common deformities include leaf curling, bushy growth, root swelling, deformed ears, and deformed fruits. For example, spraying tomato with a high concentration of naphthaleneacetic acid causes leaf curling, improper application of 2,4-D causes hollow fruits and deformed fruits; cucurbits affected by 2,4-D phytotoxicity develop fan-shaped leaves, and low-purity triacontanol easily causes young tomato leaves to curl, and so on.

Withering

This type of phytotoxicity generally affects the whole plant and is mainly caused by herbicides. For example, watermelon seedlings affected by chlorotoluron phytotoxicity show yellowing of young leaves, scorched leaf edges, and plant stunting; spraying legumes with high concentrations of insecticides causes scorching, wilting, and dead seedlings, and other phytotoxicity.

Growth arrest

Phytotoxicity caused by improper application of growth inhibitors and herbicides, such as excessive use of chlormequat causing crop growth arrest.

Sterility

The cause of this type of phytotoxicity is improper pesticide use during the flowering period. For example, applying daojiaoqing when rice is heading can cause empty and shriveled grains.

Shedding

This often occurs on fruit trees and other dicotyledonous plants, including flower drop, leaf drop, and fruit drop. For example, applying methamidophos to peach trees and applying omethoate during the flowering period cause leaf drop, or leaf drop occurs under the influence of copper-based preparations; applying methamidophos to pear trees causes flower drop; improper application of ethephon to hawthorn causes fruit drop and leaf drop.

Inferior fruit

When phytotoxicity occurs in fruits, it sometimes appears as abnormal fruit surface and deteriorated quality. For example, watermelon affected by ethephon phytotoxicity has dark red flesh and an off-flavor.