Description of the measure 

Honeybees are generally active during daylight and remain in the hive/nest at night. Therefore, changing the timing of application of the pesticide to the evening or night, when honeybees are not active, will avoid direct overspraying of the bees and reduce the risk of adverse effects.

However, bees can also be exposed to deposits of the pesticide on the plants that have been sprayed earlier. In such a case, pesticide application in the evening is only an effective risk mitigation method if the pesticide deposit degrades enough during the night not to be hazardous to bees anymore in the morning. This may be the case for pesticide residues that dissipate rapidly from the plant surface. Generally, pesticides with a residual time to 25% mortality less than 8 hours (RT25 < 8 hours) may pose limited acute risks to honeybees if applied in the evening (see Assessment Methods for more information).

Conditions for effective implementation

The pesticide should degrade rapidly on the crop/vegetation (i.e. RT25 < 8 hours).

The pesticide should not be systemic, because application of systemic pesticides in the evening could still lead to pesticide residues in pollen or nectar later on.

Estimated risk reduction potential

The risk reduction potential of this measure depends much on the speed of degradation of the pesticide on the plant. For rapidly dissipating pesticides, risk may be reduced close to 100%; for more slowly dissipating pesticides risks may still be reduced, but to a lesser extent.

Potential constraints

Spraying at night does not prevent exposure of solitary bees and bumblebees that fly at night or nest in the field or its near vicinity.

Further information

Hazard assessment for honeybees is discussed in the Assessment Methods module.

Further information on pesticide risk reduction for pollinators can be found in the MAgPIE workshop report – Mitigating the risks of plant protection products in the environment. Society for Environmental Toxicology and Chemistry (SETAC)) {INSERTLINK as soon as we have one}