The Effect of Pesticides on Bees

 Blog  •  Published on: 09 Mar 2020

Pesticides are designed to help in the battle against pests. Insecticides, on the other hand, help prevent the effects insects can have on plants. The sad thing is that insecticides end up affecting honeybees.

Insecticides can kill honey bees in a variety of ways. First, the bees might come into direct contact with the insecticides as they roam around the field. In most cases, the bees will barely get to their hives as they die immediately on the spot. Since the queen, nurse bees and brood remain uncontaminated in this variation, the colony gets to survive. The second form of contamination is more hazardous. It occurs when a bee finds its way back to the colony after coming into contact with the insecticide, either through contaminated nectar, pollen, or on its body.

Bee pesticide kills can be identified by finding a large population of bee dead outside their hive. The sudden loss of a colony’s field force might be another telltale sign. Pesticides may also later cause additional issues in the colony, such as chilled brood and brood diseases, all of which can affect the quality of your honey.

How to Prevent Pesticide Kills

Spray Pesticides at the End of the Day

While they are beneficial to plants, most pesticides might be toxic to honeybees, along with other beneficial insects. Ideally, honey bees will typically be drawn to all types of blooming flowers. As such, spraying blooms directly should be avoided at all costs. If you must spray the blooms, at least do it in the evening hours. Honey bees will mostly be active in the daylight, when the temperatures are conducive enough (above 55-60°F). They then head back to their hives once the sun begins to set. As a result, switching your spray hours to the evening can help reduce honey bee mortality rates by a huge margin.

Pick the Appropriate Formulation

Your choice of formulation can easily dictate whether spraying insecticides will result in honey bee deaths or not. Ideally, pesticides are designed in the different formulation: wettable powders (WP), dusts (D), emulsifiable concentrates (EC), soluble powders (SP), granulars (G), and solutions (LS). The best options are solutions, granulars, and emulsifiable concentrates. Unlike dusts and wettables that leave powdery residues and take time to dry up, solutions and emulsifiables are quick to dry and barely leave any residue. While granulars are a tad similar to dusts, they are larger in size. They are either broadcasted on the ground surface or applied to the soil. Since they are rarely used in blooming plants, they pose no risk to bees.

On the flip side, wettable powders and dusts will typically stick on the tiny hairs on the bees’ bodies. The particles can eventually find their way into beehives and end up being stored alongside the pollen. The entire colony can collapse were the contaminated pollen to be fed to the brood or the queen.

Use Rapidly Degradable and Less Toxic Pesticides

Using pesticides that are low on the toxicity scale and are rapidly degradable can be pivotal in reducing the mortality rates of honey bees (see the table of miticides and insecticides for pesticide residual time and toxicity). Residual time is the time it takes for the activity of the chemical to be reduced to a level safe enough for bee activity. Manufacturers have been coming up with newer pesticides whose residual times are typically short. Instead of taking days or even weeks for the pesticides to degrade once they are sprayed in the fields, it might only take a few hours.

Alter the Method of Application

The risk of pesticide poisoning can also be reduced by the mode of pesticide application used when gardening. Aerial application will expose bees to the potential risk of high fatality rates. In most cases, bee kills will occur once the pesticide moves or drifts from the sprayed target area onto the crops bees are drawn to or into the apiary. This often results in catastrophic outcomes. The risk of drift can also be increased by spraying pesticides during windy days. Methods that confine the pesticide to the target area should be preferred. This includes using methods such as soil treatments and granular formulations as they reduce the chance that the pesticides will drift off.

Establish Apiaries in Safe Locations

Your apiary’s location will have a pivotal role to play in eliminating the risk of pesticide poisoning. As long as the bees are far away from the fields, orchards, and target areas, the chances are that they can evade pesticide poisoning.

At the very least, you should place your apiary 4 miles away from crops that might be treated with toxic material and have a high chance of subjection to drift. If you happen to have your apiary close to agricultural areas that are subjected to high pesticide use levels, moving the bees can help insure them against the imminent future pesticide kills, especially considering how impossible it is to prevent bees from foraging in such areas.

For situations where moving the colonies isn’t possible, you should consider using well-ventilated screens to cover the colonies during peak foraging hours. However, these methods can be counterproductive at times as it might lead to higher mortality rates than if you were to expose the best pesticides. Since colonies might find it tough to control the temperatures of their hives when confined, the hives can easily overheat. Enough care should be taken. For instance, you can introduce water into the screens to help with temperature control. Also, avoid covering the colonies for more than two days. You could also consider providing the colonies with shade and covering them with large wet burlap sacks to help with temperature control.

Helping Bees Recover from Pesticide Exposure

Provided that the proper steps are taken, it can be possible for colonies to recover from pesticide exposure. Despite losing a majority of its field force, a colony that still has a lot of pollen and honey can recuperate without the beekeeper’s assistance.

For situations where the nurse bees and brood keep on dying, the chances are that there is still some pesticide present in the hive as well as the pollen supplies. Mortality will be high as long as the pesticide remains within the hive. The best solution would be to clean and remove the combs. Soak the combs for at least 24 hours before washing the pollen within the cells and allowing the entire comb to dry. You could also remove and replace the entire wax comb and its foundation.

You should consider feeding the colonies with pollen, water, and sugar syrup to help the colonies recuperate. Other ways that can help revive the colony include combining weak colonies, adding a package of bees, moving the apiary to pesticide-free areas with natural pollen sources and nectar, and working to protect the honey bees from the cold or heat.


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