Is the effect of pesticides related to the weather?

The toxic effects of pesticides on pests and bacteria are usually related to the weather conditions when they are used. Generally speaking, under the conditions of strong wind, heavy rain, high temperature and high humidity, the use of pesticides will reduce the efficacy, shorten the residue period and sometimes even cause phytotoxicity.

High temperature can easily promote the decomposition of pesticides and the volatilization of effective components. When the weather is hot, the chemical activity of pesticides becomes stronger, and accordingly the toxicity of pesticides becomes greater. Crops grow vigorously in hot weather, and the pores on leaves are large and open. When spraying drugs, it is easy to invade objects and cause drug damage. Therefore, in hot weather conditions, try not to use drugs, especially around noon.

The influence of high humidity on pesticides is mainly to accelerate the chemical decomposition of some pesticides, make them ineffective or cause drug damage. If the foliar humidity is high, it is easy to attach powdery pesticides, resulting in uneven application and phytotoxicity. At the same time, the dew on the leaves will dilute the drug and reduce its efficacy. Therefore, chemicals such as Bordeaux liquid and sodium fluorosilicate which are greatly affected by humidity should not be used in fog, dew or after rain. If necessary, corresponding measures should be taken, such as reducing the amount of copper sulfate or increasing the amount of lime when spraying Bordeaux mixture. Generally, it should be used in sunny, windless or windy weather.

If it rains, try not to use medicine. On the one hand, rainwater washing will reduce the efficacy and cause waste. On the other hand, it may also lead to field pollution. Generally speaking, after spraying pesticides, rainfall will occur within a few hours, which will have different degrees of influence according to the size and duration of rainfall. So when taking medicine, pay attention to check the weather forecast in advance to avoid rainy days. In addition, dew in the morning will also reduce the efficacy of most pesticides. However, in the case of powder and wettable powder, dew can promote the adhesion of drugs to leaves, which is conducive to the play of drug efficacy.

The influence of windy weather is obvious. First of all, strong wind will make the liquid medicine disperse and volatilize easily. Secondly, if the strong wind blows the liquid medicine to other crops with low drug resistance, it is easy to have phytotoxicity symptoms. Therefore, it is recommended to spray pesticides in the absence of wind or breeze.