The Effects of Neonicotinoids on Honey Bees: What can we do to minimize their impact?

In this article we are going to tackle a very sensitive topic, very relevant for today’s beekeeping: the effects of neonicotinoids on honey bees.

Let’s first take note of the current situation from which the discussion has stemmed: in December 2013 the European Commission issued a 2 year moratorium on the use of three specific neonicotinoids: imidacloprid, clothianidin and thiamethoxam. These were being used for treating the seeds of plants that are considered attractive to the honey bee (Canola, Sun-Flower etc.). This ban was introduced following the pressure from various groups that claimed the honey bees are severely affected by the three substances. From the start the opinions were very polarizing; a few laboratory studies that showed sub-lethal effects over individuals and colonies had the greatest impact.

In Romania there were exemptions from this moratorium for Canola, Sun-flower and Corn crops. This decision caused a great wave of criticism among beekeepers who considered the use of the three substances as the main culprit for the depopulation and high mortality of the colonies.

As usual, we consider that the best approach is to analyse the existing evidence, regardless if they are favorable or not and only after that to find the solutions. We will start off with the ones showing the negative effects of neonicotinoids on the honey bees. The vast majority of these studies were carried out in a laboratory and eventually led to the above mentioned moratorium.

A relevant example of such a study that caused a lot of emotion was the one carried out by Italian doctor Vincenzo Girolami. In this experiment the bees consuming the liquid from the guttate of corn crops containing traces of clothianidin died after a short period. This is how the guttate of corn looks like:


The experiment is shown in the video below:

The tests performed in the field in 6 different locations with different climatic conditions from Austria and France, around areas of corn crops, showed that only a very small number of bees had signs of intoxication with insecticide. The most relevant of these studies was one performed in Switzerland by independent expert that showed no signs of intoxication with clothianidin.

It is precisely this difference between lab and real world tests that led to the temporary ban of two years for the use of neonicotinoids. It is clear that these studies cannot provide sufficient relevant information like the once performed in the field. Two years were considered enough for gathering enough data from real world studies. Here are the results from the most popular field studies:

1. In 2011 Chauzat analyzed 187 pollen samples harvested between 2002 and 2005 from France. In 40.5% of these sample he found traces of imidacloprid of up to to 5.7 ppb (parts per billion), but with an average of only 0.9 ppb;

2. Other studies carried out in the same period in Sweden, France and UK showed traces of less than 10 ppb;

3.In more recent studies published after 2012 there were identified quantities between 1.5 and 5 ppb;

4. In a four year study performed in three locations from France there were identified traces of thiamethoxam of less than 1 ppb in the plant’s stem and pollen and between 0.7 and 1.7 ppb in the plant’s nectar (Pilling et al, 2013);

5. A recent study published in Canada (Cutler et al, 2014) that analyzed several samples of nectar, pollen and wax from colonies located around canola fields showed that the vast majority of the samples had no traces of insecticide and a small number showed quantities of clothianidin between 0.5 and 2 ppb;

6. The latest data comes from the USA; the EPA (Environmental Protection Agency) concluded that quantities of more than 25 ppb imidacloprid can cause sub-lethal damage, but only in the case of plants that provide nectar and recommended restricting the use of imidacloprid on nectareous crops.

Solutions for reducing the effects of the potential negative side effects of neonicotinoids

Despite the above mentioned findings, there were some good news – if we can call them that way. Let us see what the good parts are and identify the solutions that will help us minimize the negative effects of these substances:

1. The mixed findings of the studies and the fact that the tests showed different results when compared to the ones carried out in laboratories (when large doses of insecticide were introduced directly into food) hint to the first optimistic conclusion: the problem with exposure to neonicotinoids depends greatly on their concentration, duration and choosing a relatively safe location during nectar flow.

In fact, it is a well known fact that in chemistry dosage and exposure are key elements that make the difference between toxic and beneficial. The conclusion of these experiments only comes to confirm this already established fact. The difference between lab testing and real world conditions regarding the quantity of ingested substance relative to the time it takes to be consumed is around 7 days. During lab testing, the food was consumed immediately, in one take, while in real world conditions it took around 7 days. During this interval the honey bee has the proven capacity to detoxify a large part of the ingested insecticide, in the same way it does with propolis or pollen. Also, the bee will regurgitate nectar shortly after arriving to the hive, which further shortens the exposure to the insecticide. Once it is placed in the comb, the nectar will be ventilated, decreasing the amount of insecticide. If it isn’t used as food immediately it will be mixed and diluted with uncontaminated nectar.

Considering the above mentioned aspects, there are two solutions to attenuate the potential negative side effects of neonicotinoids: short exposure to crops that were treated with neonicotinoids and supplemental feeding after the nectar flow to help dilute the insecticide residues.

Another element that drastically reduced the impact of neonicotinoides was the presence of several harvesting sources around monocultures. This aspect wasn’t taken into consideration during lab testing, but field experiments showed that honey bees will use several sources when given the opportunity.

2. The second good news is related to what was originally thought with regards to the large quantity of insecticide dispersed on the plants surrounding monoculture crops. This aspect was highly covered in media following an incident from 2008 in Germany when, due to the weak fixation of the insecticide on the seeds, large quantities of the substance were dispersed around the crops, leading to high mortality among honey bee colonies. We are of course talking about a lethal and not sub-lethal effect that looked like this:

Regarding this incident and until we have a clear resolution regarding the ban on the use of neonicotinoids, we must make sure that the working procedures are respected by the parties using these substances. These include:

  • the use of pneumatic seeders (as the legislation requires);
  • the use of seeds from certified and authorized sources as opposed to seeds that were treated by individual farmers that will cause massive dispersion of the insecticide. Even so, another good news came from the same Vincenzo Girolami who showed in a 2011 study that in the case of low humidity, the honey bee can cope with quantities of powder insecticide of up to 25 times higher as it will get rid off most of it during flight. The problem is high humidity.

Options for protecting the honey bee: we must make sure that the above mentioned procedures are followed and avoid areas with crops that were treated with neonicotinoids during periods of high humidity. The problems is particularly present with canola crops when there are corn or sun-flower crops near by.


3. The third and most important solution – avoiding the honey bee stress:

  • Nutritional stress
  • Disease stress
  • Thermal stress
  • Physical stress

Nutritional stress

Considering that insecticide exposure already causes a major stress to the honey bee, it is vital for the beekeeper to take any precautionary measures to eliminate or at least minimize the impact of other types of stress that the honey bee is subjected to throughout the year. While insecticide exposure is difficult to control as it largely depends on a third party, we must acknowledge that there also cases where, through bad management, the beekeeper only causes these effects to get worse.

A prime example is during sun-flower nectar flow. Throughout the harvest, the pollen source of the colonies is only one (since we are talking about a monoculture). As we have previously showed, sun-flower pollen is extremely inappropriate for the honey bee’s nutritional needs. This will lead to a nutritional stress of the young bee that must for its fat body during the first days after hatching. This phenomenon also explains why there was massive depopulation during sun-flower nectar flow, even though neonicotinoids were yet to be used.

Disease stress

Considering the above mentioned example, we must not forget that also during sun-flower nectar flow there are massive infestations with Varroa. Even if the treatment is carried out after the sun-flower nectar flow, the viruses transmitted through Varroa mites will continue to cause depopulation for a long period. We are talking here about a second type of stress for the honey bee. Keeping Varroa under control through organic treatments (formic acid or oxalic acid) is an efficient way for reducing or eliminating Varroa induced stress.

Thermal and physical stress

The two types of stress mentioned before can also be aggravated by extreme temperatures during July through August, but also by the faulty positioning of the hives that confuses the honey bee and facilitates the transmission of diseases from one colony to the other. The correct placement of hives during harvest (considering the distance from the nectar source and avoiding the placement of the hives in one continuous line) can contribute to a better sanitary condition of the colonies. We will be talking more about the different types of stress in future articles. As it is the case with many living creatures, stress is often the culprit of various problems despite the use of correct procedures of selection, nutrition or treatments.

As a conclusion, by implementing an adequate management, we can minimize the impact of neonicotinoids on honey bees. This way, until there will be conclusive evidence and clear procedures with regards to the use of neonicotinoides, we won’t suffer from continuous loss of honey bee colonies.

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