Damage from Pesticides to Bees

Bees are most exposed to contamination during foraging and water collection operations. During these operations, they can come into direct contact with these substances. This occurs when they fly over plots during a treatment or forage for wild flowers below or adjacent to the treated crop. They can, however, also come into contact indirectly, feeding on contaminated nectar and pollen and in turn feeding the brood. Monitoring projects such as BeeNet have found heavy contamination of pollen collected by bees. More than 50% of pollen samples taken from sampled hives contain at least one active ingredient used in agriculture. Studies have in fact confirmed the presence, at low concentrations, of pesticides in the nectar and pollen of plants treated with systemic products.

Assessing the effects of a certain pesticide on the hive can be very difficult. Indeed, it is not sufficient to establish the level of direct mortality, but it is always necessary to analyse the sub-lethal effects of a certain product that can still lead to colony loss. Sub-lethal doses may in fact be responsible for the decline in social behaviour. This involves alterations in the communication and orientation system, effects on the queen such as poor laying and a reduction in the 'quality' of the brood and future adult bees.

The suspicion of poisoning by plant protection products in the vicinity of cultivated areas is greatest at certain times of the year corresponding to the main crop protection periods. In general, poisonings may occur in spring for sowing maize with tanned seeds, in conjunction with pre- and post-flowering treatments in orchards. In the same period, fertigation treatments are also carried out on melon and watermelon. In summer, on the other hand, problems may arise for compulsory treatments against the vine leafhopper and in conjunction with mosquito control treatments. By contrast, fungicides and herbicides are probably less harmful to bees. However, studies suggest that they may cause sub-lethal effects such as malformations and metamorphosis alterations on juvenile stages.

Following poisoning, a more or less sudden depopulation of the hive can be observed. Depopulation is very rapid if the brood is fed with freshly collected contaminated foodstuffs. It is instead slower if pollen is stored. High concentrations of pesticides may be responsible for numerous dead, moribund, unviable or nervous bees in front of the colony. More populous and strong hives often suffer more damage than weak families. The queen in the case of severe poisoning may also stop ovipositing. The presence of a high varroa infestation or other diseases such as Nosema can make bees more susceptible to the toxic principles contributing to the loss of the family.

To date for bees there is no antidote or cure for pesticide poisoning. It is important to try to keep the affected hives vigorous by changing the queen if a decrease in laying is noticed. In the case of a slow and progressive depopulation, indicative of contamination of stored pollen and nectar, it is a good idea to replace combs and proceed with sugar and protein feeding. If the problem persists, moving the apiary may be the only solution.

It is essential to report the phenomenon as soon as possible to the competent ASL, which will carry out analyses to prove the presence of active ingredients in bees. If the poisoning is confirmed by the analyses, the Regional Phytosanitary Service will proceed, directly or through the Provincial Agricultural Services, to ascertain the violation. This is done by means of an inspection on the farms that presumably caused the damage with the use of irregular pesticide treatments. The inspection may also involve taking plant material. The beekeeper is then subject, after ascertaining the violation, to compensation for damages as stated in Article 2050 of the Civil Code.

Dialogue between beekeeper and farmer plays a key role in preventing these phenomena. In addition to the correct use of pesticides and compliance with the strict rules for carrying out phytosanitary treatments, it is important for the farmer to inform beekeepers about the planned treatments. In this way, the apiary can be moved at an appropriate distance to preserve colony health. To limit damage, pharmaceutical companies should also put more effort into the development of low-toxicity pesticides. This problem is in fact very often ignored despite its seriousness. Currently, one of the tricks every beekeeper should put into practice is that of choosing the right location for their apiaries. Opting for pristine locations, far from sources of pollution and crops, especially intensive ones, is the best solution. This allows you to protect your bees better and avoid poisoning incidents.