1. Determine the spraying time based on temperature and its trend
Whether it is plants, insects or pathogens, 20-30℃, especially 25℃, is the most suitable temperature for their activities. Spraying at this time will be more effective for the pests, diseases and weeds that are in the active period, and safer for the crops. During the hot summer season, the spraying time should be before 10 a.m. and after 4 p.m. In the cool seasons of spring and autumn, it should be chosen after 10 a.m. and before 2 p.m. In greenhouses in winter and spring, it is best to spray in the morning on a sunny and warm day.
II. Determine the timing of pesticide application based on humidity and its trend
After the pesticide solution sprayed from the nozzle deposits on the target, it needs to spread out to form a uniform film on the target surface in order to cover the target surface to the greatest extent and “suppress” the pests and diseases on the target. The process from deposition to expansion of the pesticide solution is affected by various factors, among which the influence of air humidity is significant. When the air humidity is low, the moisture in the pesticide droplets will quickly evaporate into the air, and even before the pesticide solution can spread on the target surface, this will inevitably reduce the efficacy of the pesticide and even cause burning-type pesticide damage spots. When the air humidity is too high, the pesticide solution deposited on the plant surface, especially large droplets, is prone to coalesce into larger droplets and be affected by gravity to deposit on the lower part of the plant again, which will also cause pesticide damage. Therefore, the timing of pesticide application during the day needs to follow two principles: one is that the air humidity is slightly dry, and the other is that the pesticide solution can form a dried pesticide film on the target surface before sunset after application.
III. Three Common Misconceptions in Pesticide Application
1. Simply determining the amount of pesticide in each bucket based on the dilution ratio
Most people are accustomed to calculating the amount of pesticide to be added to each bucket based on the dilution ratio. However, this is not very reliable. The reason for controlling and calculating the amount of pesticide to be added to the pesticide container is to determine the appropriate dosage of pesticide for each plant area to ensure good efficacy and safety for the plants and the environment. After adding the appropriate amount of pesticide to each bucket based on the dilution ratio, it is necessary to calculate the number of buckets needed per acre, the spraying speed, and other details. Currently, due to the limitation of labor, many people often add more pesticide to the pesticide tank and spray quickly. This reversed approach is obviously incorrect. The most reasonable measure is to choose a sprayer with better spray performance or to add the pesticide according to the product instructions and spray carefully.
2. The closer the nozzle is to the target, the better the efficacy
After the pesticide liquid is sprayed from the nozzle, it collides with the air and breaks into smaller droplets while rushing forward. The result of this chaotic movement is that the droplets become smaller and smaller. That is to say, within a certain distance range, the farther away from the nozzle, the smaller the droplets. Smaller droplets are more likely to deposit and spread on the target. Therefore, it is not necessarily true that the efficacy will be better when the nozzle is close to the plant. Generally, for backpack electric sprayers, the nozzle should be kept at a distance of 30-50 centimeters from the target, and for mobile sprayers, it should be kept at a distance of about 1 meter. By swinging the nozzle to allow the pesticide mist to fall on the target, the efficacy will be better.
3. The smaller the droplet, the better the efficacy
The smaller the droplet is not necessarily better. The size of the droplet is related to its better distribution, deposition, and spread on the target. If the droplet is too small, it will float in the air and be difficult to deposit on the target, which will definitely cause waste; if the droplet is too large, the pesticide liquid that rolls onto the ground will also increase, which is also a waste. Therefore, it is necessary to select the appropriate sprayer and nozzle according to the target of control and the spatial environment. In a relatively enclosed greenhouse for controlling diseases and whiteflies, aphids, etc., a smoke machine can be chosen; in open fields for controlling these diseases and pests, a sprayer with larger droplets should be selected and used.
Post time: Nov-26-2025