What every farmer needs to know about pesticide weather considerations
The importance of weather in pesticide spraying
There is a limited amount of time to control pests and diseases for crops. As the time window opportunity might be even shorter due to unsuitable weather, applicators need to be able to identify and plan accordingly.
Weather plays a huge role in pesticides application timing. It can significantly impact the amount of pesticides that are sprayed, their effectiveness, and the risk of causing harm to the plants and the environment.
The 4 key weather factors in pesticide application success
The four key factors that affect weather and pesticides are temperature, wind, precipitation, and humidity. The worst weather conditions for spraying are strong wind, high temperature, intensive rain, and low humidity. The wind is the most crucial factor because it affects how pesticides move through the air; in extreme cases the application will not affect the plants. Precipitation can also change how pesticides are distributed, but it has a more minor effect than wind movement. Finally, humidity affects how much water is in the air, which can also affect pesticide distribution. Pesticides can be applied as a liquid, powder, or gas. The pesticide used depends on the crop and pest to be controlled. The method of application should also be added to the set of considerations when weather conditions are considered. For example, herbicides can evaporate at a greater rate when sprayed under high temperatures, while fungicides can freeze at lower temperatures.
Temperatures of air and surfaces are important factors in the efficacy of pesticides. Different chemical compounds have different temperature ranges at which they are most effective. For example, the insecticide pyrethroid is most effective at temperatures higher than 50°F.
Spraying pesticides outside is not recommended when there is more risk for a high evaporation rate, degradation, and extended droplet lifetime. These factors increase the chance of drift. Degradation of pesticides can be increased when the humidity is high. High humidity also decreases evaporation, resulting in extended droplet lifetime and increased drift risk. These also play an essential role in safety. Higher concentrations of pesticides in the air can lead to potential health risks for workers and nearby residents. Some pesticides are more sensitive to temperature changes than others. In warm weather, humidity should allow good evaporation conditions. This will ensure that the pesticides have less time to break down into toxic compounds while contacting the plants. Decisions on spraying in such cases become challenging as high temperatures make plants more vulnerable to pests and diseases. Their natural defense systems break down and become more susceptible to pests and diseases like fungi and insects. Therefore, applicators need to carefully choose the timing of spraying to protect plants in such weather conditions.
A better way of telling how quickly pesticide droplets evaporate is the Delta T indicator. Delta T is the difference between wet and dry bulb temperatures, which can be calculated by combining the effect of temperature and relative humidity.
When the temperature increases with the distance from the ground, it is said to be an inversion. The inversion hazard is often highest from dusk to a few hours after sunset and weak at sunrise. Spraying should be avoided in this case as the risk of drifting pesticides to long distances is high.
The wind can carry agricultural pesticides far away from where they were sprayed, making them drift onto other people’s property. This decreases the effectiveness of the spraying and increases the risk of polluting the environment and harming people living in nearby areas. This is why farmers must take into account wind direction when spraying their fields with agricultural pesticides.
Rainfall can have a significant effect on the efficacy of pesticides. Rain has been shown to reduce pesticide wash out in some instances and increase pesticide wash out in others. The primary function of systemic pesticides is to be taken in by the roots, but the rain needs to be relatively light for this to happen without the effect of washing the active material away from the plant surrounding. In general, the plant will absorb most of the systematic pesticide solution within about 2-4 hours. Therefore, it is essential to know how long you need to spray before the rain starts in order to get an acceptable level of control.
Generally speaking, the best time to spray is early morning or late evening when there is little wind, and the temperature is cool. In the case of insecticide, the evening is preferred as the interference with bees is minimized.
How technology can help you with timing spraying
With constant hyper-local weather monitoring and forecasting, we can show you the best spraying opportunities in the Agrio app. We save you time and present you with this information when you decide on a spraying application. In addition, our weather forecasts update every hour, so you can stay updated when forecasts are changing.
Once a spraying strategy is planned, we help you keep a record and send you reminders in due time.
Using weather predictions to optimize treatment timings is an essential tool that will help you to optimize pest and disease control in your fields. We look forward to seeing you leveraging this technology for intelligent and effective pest management in your field.
In the meantime, as always, we wish you an abundant harvest.