Could garden sprays be killing your bees?

by Hilary Kearney 5 min read

There is nothing worse than discovering your bees have been poisoned. The entrance, once a busy runway for arriving and departing foragers, now silent with only a few twitching bees in the pile of dead below. The suddenness of a colony lost to pesticide poisoning is shocking. What follows is often heartbreaking, humbling and infuriating. So, how can you tell if your colony has been poisoned, what can you do about it and how do you stop it happening in the first place?

Recognising pesticide poisoning

Since honey bees will fly up to three miles to forage, urban beekeepers find themselves at the mercy of their neighbours when it comes to pesticide usage. Unlike agricultural settings, most urban and suburban homeowners are free to use pesticides without restrictions, licensing or instruction. Improper use of pesticides can devastate nearby beehives. Improper use includes using too much, applying it to plants when they are in bloom, or applying it at the wrong time of day. It’s important to understand that the majority of these incidents happen as a result of ignorance, not malice. Many simply fail to read instructions before using the product they buy and do so without an understanding of the consequences of their actions.

When your colony experiences acute pesticide poisoning, you will see:

  • A sudden drop in foragers
  • A large mat of dead bees in front of your hive
  • Spinning, skipping and disoriented bees on the ground around your hive
  • Bees dropping from the frames when you lift them out
  • Dead bees on the bottom board.

The rooftop apiary of a student of mine was recently poisoned and exhibited all of those symptoms. Her two new colonies were thriving and just beginning to fill their second brood box with comb when disaster struck. Nearly all of the foragers were poisoned. Many of them never made it back to the hives, but several hundred did and unfortunately, they passed on the poison to the house bees. When this happens, you will find dead bees inside the hive and young bees will drop off the frames when you lift them out. At this stage of poisoning, a colony’s chance of survival is minimal. However, luckily, in this case after three weeks her queens are still alive and laying well so we are hopeful that they will recover.

How to help a poisoned hive recover

Sadly, most poisoned hives never recover, but in most cases it is a simple numbers game. The bigger your colony is, the better its chance of survival. Once pesticides knock out the field bees, the population will be drastically reduced. A hive with a low population is now at risk for a number of other problems because it will not have the necessary workforce needed to complete daily tasks.

One big one is cleanliness. A poisoned hive can easily become overwhelmed with the housework or cleaning out dead bees and any poisoned larvae. You can’t do much to help this, but if you notice dead bees on the bottom board, be sure to clear them out of the hive to prevent any secondary bacterial infections from taking hold.

Another big problem is food stores. Without foragers, your bees will be forced to live on what they have. If their stores are low, they can end up dying of starvation! Make sure your bees have enough pollen and honey stores and if they do not you should feed them until they can build up their population again.

It is very common for a poisoned colony to end up queenless and it does not always happen right away. You should take special care not to overlook the symptoms of a colony that has lost its queen. If you notice your bees are making new queens, you should let them or replace her yourself. It is likely that your queen has been damaged or killed by the pesticide exposure.

As a rule of thumb, I recommend you reduce the entrance whenever a colony is weakened to protect them from predators. Be sure to do this when your colony is recovering from a poisoning as well as they will be extremely vulnerable.

Lastly, a colony whose population drops suddenly can also fall victim to mites, moths and beetles. Keep a close eye out for these villains in the weeks following the poisoning and take appropriate action against them if you see any signs. It’s a good idea to head off moths and beetles by removing any abandoned comb. A weakened colony may not have the resources to defend all of the combs they once occupied.

Preventing pesticide poisoning

We cannot control where our bees go to forage, but what we can do is educate our communities about protecting our pollinators with responsible pest management practices. Some strategies for reaching your neighbors include: door-to-door canvassing with educational pamphlets, posting on online community forums, contacting local leaders or news organisations, volunteering to speak to garden groups. Here is some useful information to share when employing these outreach strategies.

  • Pesticides are not always necessary. When a plant is under stress, it’s susceptible to pests and other problems. When you use a pesticide or a fungicide you are really only treating a symptom and not the problem. The problem often lies in the soil. Poor soil health leads to weak plants which leads to pest problems. So, before dousing your plant in pesticides, you might want to investigate whether the soil needs to be amended.
  • Pick your poison carefully. Some pesticides are more harmful to bees than others and even the ones that are less harmful can still do damage when applied incorrectly. If you feel that you need to use a pesticide, research which ones are most appropriate and least harmful to the bees.
  • Application matters. Always read the directions on your pesticide product, but in general to protect pollinators, you should not treat plants that are in bloom. It is also important to apply the pesticide in the evening so that it is less likely the bees will encounter it and you should not apply the pesticide in windy or wet conditions because this can lead to drift.

Hilary Kearney is a full-time beekeeper in her home town of San Diego, California. Her business Girl Next Door Honey educates hundreds of new beekeepers each year. She is the author of the Beekeeping Like A Girl blog and maintains popular Instagram, Facebook and Twitter accounts. When she’s not rescuing bees, teaching about bees, photographing bees or managing one of her 60 colonies, she’s sleeping and dreaming of bees.

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