Pesticides Close to Home.

Photo from Wikkicommons.

Home Owners Use More Pesticides.

Did you know that home owners/householders generally use more pesticides per unit of land than agricultural producer do in the US, and they often use harmful chemicals on their pets such as neonicotinoid flea treatments?  Do you think that here in UK it will be very different?

Yue et al1 surveyed home owners and discovered that they prioritized efficacy, safety of people and pets, and ease of use. So, using harmful pesticides regularly in this setting is born of ignorance rather than malice. Here in the UK, we currently have a problem with harmful veterinary medicines prescribed and used to target internal and external parasites in pets. These include worms, fleas, and ticks. Imagine how many horses in the UK get wormed with even larger amounts of harmful stuff?

Flea Treatments.

Five pesticides not used in agriculture are commonly used in flea treatments and they are leaching into our water courses posing human health threats and danger to aquatic life. Two of them impact negatively on our endocrine systems and cause cancer. What is shocking is that the neonicotinoid Imidacloprid was banned in the UK and last used in agriculture back in 2013. In that final year 5,407 kg was applied to crops throughout the UK. However, the amount of active ingredient used in flea and tick treatments sold by the UK manufactures in 2017 was a staggering 4,000 kg.

Pesticide Action Network UK.

The list below is taken from Pesticide Action Network UK (PAN UK). You can support the open letter to the UK Government calling for a ban on these chemicals by using this link:

  • Fipronil  (used in Frontline Plus above) – no plant protection products ever approved in the UK but found in 483 parasiticide products for cats and dogs. Detected at 105 (37%) of river sites tested. At all sites, levels of fipronil exceeded the Predicted No Effect Concentration (PNEC), the level above which adverse effects for aquatic wildlife can be expected.
  • Imidacloprid – banned for use on outdoor crops in 2018 but found in 176 parasiticide products for cats and dogs. Detected at 22 (8%) out of 283 sites. In just under half of these sites, the amount of imidacloprid was above safe levels for wildlife.
  • Permethrin – banned for use on crops in 2002 but found in 90 parasiticide products for cats and dogs. Detected at four sites between three and seven times the safe level for wildlife.
  • Dinotefuran – never approved for use on crops but found in 12 parasiticide products for cats and dogs. Not present in Environment Agency testing data
  • Nitenpyram – never approved for use on crops but found in nine parasiticide products for cats and dogs. Not present in Environment Agency testing data

Emotive Topic.

The subject of pesticides in beekeeping is an emotive subject. It’s really a mine field; just post something about them on social media and watch the responses. Because we still know so little about the long-term effects of chemicals, and we read conflicting accounts and sensationalized media reports, it is a confusing topic and hardly surprising that there is so much controversy around them. For example, should UK sugar beet farmers be allowed to use neonicotinoids in an emergency situation, or not, remains a much-debated topic.

What is Toxicity?

To better understand pesticides and their dangers it is worth learning a little about what toxicity is because this can help us work out the level of risk that each chemical poses.

Before a pesticide is registered for use, the LD50 and LC50 values are calculated for each active ingredient in the pesticide. There are other ingredients known as adjuvants which are inert substances that make the main ingredients work better. At the moment, not a lot of attention is being paid to adjuvants, but some of them are toxic to bees2.

So, what do these values mean? The LD50 is the dose that kills 50% of a honey bee population in a short time. It is known as the lethal dose. The LC50 is the concentration of pesticide that kills 50% of the population of bees in a short time period. This is known as the lethal concentration.

Measuring Toxicity.

The usual way of measuring whether a pesticide is toxic to bees is by measuring acute toxicity which is what decides the dose of pesticides that will kill a bee in a certain time. Bees are exposed to different concentrations of toxins either through being fed a solution (oral), or by toxins being applied to their body (contact). The usual time of measuring the results is after 24 hours of exposure but it can be measured at other points up to 96 hours. If bees die shortly after exposure, then this is acute toxicity. So, honey bees dying during foraging or shortly after returning to the hive from a treated crop treated with pesticides have died from acute toxicity.

From McArt, et al, 2017.

So, how can we tell from the LD50 value what the degree of toxicity is? A value of less that 2 micrograms per bee is highly toxic. Between 2-10.99 micrograms per bee is moderately toxic, and levels of 11 or more micrograms per bee are almost non-toxic.

You can see from the chart above that the first 9 insecticides are highly toxic and pose the greatest risk. However, just because fungicides are non-toxic and don’t kill bees immediately, we know that they interfere with honey bee gut microbiomes and can negatively affect nutrition and immunity. We still know so little about the sublethal and longterm affects of pesticides.

Reducing Risks.

What significant steps could growers, beekeepers, landowners, homeowners, and the general public take to reduce pesticide exposure to bees?

The main step common to all groups is to stop using pesticides prophylactically and adopt an Integrated Pest Management (IPM) strategy in any setting. This involves monitoring pest levels, assessing risk, and using pesticides only when crops, plants, and animals are at greater risk of damage than if left untreated by chemicals.

IPM involves using biotechnical methods of pest control and management strategies, and employing pesticides only as a last resort. Using organic chemicals, essential oils or companion planting in gardens are effective alternatives. The latter involves planting flowers like marigolds among vegetables because they contain pyrethrum and give off volatile insecticides. Interestingly, marigold insecticides are toxic to mosquitoes.  Certain predators such as ladybirds eat aphids and avoiding insecticides encourages more of them. Instead of the gardener spraying plants with pesticides soapy water can be used instead.

Garden centres often advertise bee friendly plants for sale but ironically many are treated with neonicotinoids. Banning pesticides is controversial and it is possible that even more toxic chemicals might be used instead. However, neonicotinoids have been banned for some years in Europe, and in the UK, it is only possible to use them on certain crops sugar as sugar beets under certain conditions and derogations.

Landowners, growers, and agriculturists and beekeepers can communicate with each other over when and what will be used where pesticides are used. Schemes such as “Bee Connected” in UK operate when beekeepers join and then they are given at least 24 hours warning of imminent spraying.

Spray operators can ensure that spraying takes place at night, or very early morning before the bees go out flying. Weather conditions must be taken into consideration and spraying is not carried out on windy days to reduce drifting. Ground applications rather than aerial applications should be administered. Spraying is to be avoided when plants are in bloom and this includes nearby weeds. It is important to avoid dust which spreads pesticides more readily but this seems unavoidable when treating corn and soybean crops which have coated seeds and have a higher associated honey bee mortality.

Pet owners using harmful treatments need to bag and bin all pet faeces.

Beekeepers can reduce risks by screening hive entrances in some situations. However, overheating is always a risk so providing extra space by adding an empty hive body and giving water during the time bees are confined can reduce risks. In some settings, and where there are only a few colonies, it might be appropriate to use garden sprinklers turned on the hives to simulate rain during spraying during the day to prevent foragers leaving home. Where possible, beekeepers can choose apiary sites that are lower risk and away from crops that are treated with chemicals3. They can better protect their bees by making themselves known to local farmers and finding out what crops are being grown and what treatments are used.

Other measures that beekeepers can take are to keep colonies healthy, strong and disease-free with young vigorous queens. They can promote propolis producing colonies to boost immunity and protect against infection. Old frames containing entombed pollen and pesticide-laden wax can be changed out on a regular basis to reduce risks of resistance to the varroacides which are trapped in wax and being released constantly in small doses. Nutritional supplements can be given because adequate protein, fat, vitamin, and carbohydrate intakes can help reduce the negative impacts of pesticides.

All groups can lobby Governments to change the laws on risk assessment and pesticide testing before releasing new products. Current research shows a failure to assess sublethal, and long-term effects on honey bees, the effects of inert ingredients (adjuvants), and the effects on other pollinators such as native bees2. Along with positive action, good communications between all the stakeholders are key to reducing pesticide risks for honey bees.

Policy makers, health departments, farmers, beekeepers, and everyone interfacing with the public need to somehow get the message across regarding the dangers of using pesticides, and give advice about the safer alternatives, some of which are easily and cheaply available. Why not set up an educational stand at your next beekeeping association honey show or outreach day and raise awareness?


1C. Yue and T. Hurley. Estimating the Economic Value of Neonicotinoid Insecticides on Flowers, Shrubs, Home Lawns and Trees in the Homescape. AgInfomatics, Madison, Wisconsin, 2014. Accessed 1 December 2018.

2S. McArt, How to Make Pesticides Safer for Bees, January 2024, Americal Bee Journal pp 57-60.

3G. Zhang, R. Olsson, and B. Hopkins, Strategies & Techniques to Mitigate the Negative Impacts of Pesticide Exposure to Honey Bees, Environmental Pollution, Volume 318, 1 February 2023, 120915.

4 thoughts on “Pesticides Close to Home.”

  1. An exceptional account of a very concerning problem. Much of this could be solved by public education and awareness – alas, what government has the budgets to counter the marketing clout of the big Pharma and Chemical giants?

    Your account saves me weeks of trawling through the internet for the pertinent facts, Ann – I’m very grateful to you for taking the time to help us all understand.

  2. What a great article Ann. It is very sad that big pharma has jumped on the rising pet keepers to get their pesticides out there. There are alternatives like Diatomaceous earth for worming and for fleas. wearing a mask is advised as it can get into lungs but the harm is not the toxicity but the tiny sharp fossils in it that break down the skeletal body of the fleas etc. How many people wear a mask when they put flea powder or dab on chemicals on the fur of their animals? Horse wormers are incredibly toxic to the environment and not particularly good for the horses health. Again DE can be used as well as good grazing management and grass / plant diversity for the horse. Worryingly we put this on our vegetables when we get manure from stables etc. My family has a small farm with horses, pigs, sheep, cows hens and use DE for worming as they don’t want any chemicals on their land. They also use garlic. They send their poo samples off for testing every six months.
    When I had hens I used a mixture of wormwood, turmeric, cayenne pepper, garlic, DE, thyme, rosemary and mixed it with their feed as well as a little apple cider vinegar in their water.
    Of course everyone can’t do this but if we want to reduce the use of these harmful chemicals for the bees and all wildlife as well us ourselves then we have to look at what we are putting on our pets and into our pets. Pets have never been so unhealthy. I believe good vets are now questioning the use of pesticides on our pets and what it is doing to their health and ours as well as our water and soil. A good book for looking at alternatives is Juliette Bairacli Levy The complete herbal handbook for the dog and cat. Also there are many others out there too. As always we need to use common sense as we can go down so many rabbit holes on the internet!

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