Changes in cropping systems can have an impact on the use of pesticides. The lengthening of the rotation of cultures makes it possible to alternate the spring crops and the winter crops in order to break the cycles of the pests. Pests being fewer, the use of pesticides is less necessary. Thus, in order to reduce the pesticide use, longer and more diversified rotations are necessary.
In the case of very short rotations, pests specialise in one type of crop (for their feeding) and get a specific reproduction cycle that fit with the crop rotation. The impact can be important when the climatic context is favorable.
Unlike fertilisation, the division of doses of pesticides is rarely recommended because it is assumed that it increases the resistance of pests. In fact, in order to reduce the doses, it is often recommended to use two different active ingredients at lower doses.
The pesticide spraying is recommended when temperatures are low and relative humidity is high. In general, it is better not to spray when relative humidity is less than 40 per cent and air temperature is above 25°C. This reduces the chance of drift due to temperature inversions or evaporation. Then, optimum spraying conditions are generally early mornings.
The splitting/frequency of pesticide application is, in form of the treatment frequency index (TFI) well established as indicator. Timing of pesticide application may have a strong influence on pesticide losses to the environment, but to establish the data record may be difficult.