Pesticide alternatives kill bees too

organic pesticides kill bees
Shawn Caza

Pesticides. It’s just one of those words that make you cringe. We’ve been wary of them for years, and recent pollinator declines aren’t making us feel any more approving. What many consumers and policy-makers fail to realize, though, is that organic alternatives might not be much better. 

Until recently, organic-approved pesticides haven’t really been a cause for concern. This is because organic farms are mostly restricted to natural products, and it’s usually assumed that natural products are safer. However, a few studies released this year suggest that may not be the case. In fact, some natural products might even be worse than conventional ones.

Is organic farming really killing bees? Click To Tweet

Natural Pesticides Are Still Poisons

One of this year’s studies came from a group of researchers in Brazil, who examined the effects of botanical insecticides on honeybees. The study included several plant oils, garlic extract, and rotenone, all of which are approved for use on organic farms. Surprisingly, the group reported that many of the substances caused death in either adult and larval bees and that exposed larvae developed into smaller and less-active workers. They also found that males often developed into deformed adults.

But those aren’t the only products that cause problems. A variety of other botanicals have also been found to poison bees. Some, like pyrethrins, are just natural versions of the toxic pesticides they’re meant to replace. The active ingredients are so potent and indiscriminate that they kill almost any kind of invertebrate, including natural enemies, pollinators, and even crayfish. In fact, azadirachtin, which is the active ingredient in neem oil, might even be worse for bees than the synthetic neonicotinoids that have become so controversial.

Last year, a group of scientists from Brazil and Belgium investigated the effect of azadirachtin on bumblebees and found that the compound increased mortality, while also decreasing egg-laying activity and stunting development of reproductive organs. Most alarming was that even at 10% the recommended application rate, azadarachtin caused more damage to the bees than the neonicotonoid imidacloprid.

Studies show organic pesticides are just as harmful to bees. Maybe worse. Click To Tweet

Biological Control

As it turns out, even sticking to biological control for pest management can put pollinators in harm’s way. A study that was released just last week examined the effects of parasitic nematode products on the bumblebee Bombus terrestris. The group found that exposed bees experienced more than 80% death within only a few days, and that the nematode species in one product were lethal even when applied below recommended levels. They also determined that the most harmful nematodes were able to reproduce inside the dead bees, after which they could infect the rest of the colony.

Another “beneficial” organisms is the fungus Beauveria bassiana, which is used to control insect pests by causing white muscadine disease. But Beauveria also infects beneficial insects and has been shown to decrease the lifespan of bumblebees. Spinosad, which is another biological pesticide, kills bees too. But that’s not it…

Fungicides and Bee Health

Yet another problem facing pollinators on organic farms is their exposure to toxic fungicides.  Copper sulphate, for example, is highly toxic to bees according to the Xerces Society for Invertebrate Conservation. Researchers from Wittenberg University and the USDA also found that fungicides decrease the amount of beneficial fungi in honeybee colonies. The effect was even observed when the fungicides were sprayed before flowers were in bloom, and the fungicide exposure seems to increase the susceptibility of the bees to disease, including both chalkbrood and Nosema infection.

“Organic” Isn’t Helping

After reading this, you might not be surprised that organic practices aren’t helping pollinators as much as we would have hoped. Not only are organic-approved products a lot more toxic than we thought, but evidence is beginning to show that reducing pesticides isn’t really what bees needed anyway.

Instead of decreasing pesticides or switching to organic practices, studies are now showing that increasing the availability of natural habitat could be more beneficial. Although it’s true that pesticides have been associated with declines in wild pollinators, several studies have shown that available habitat has more of a positive effect on pollinator abundance than organic practices. The effects of pesticides also seem to be buffered when farms increase the proportion of natural habitat in their landscapes.

Fewer positive results have been seen for wild bees and wasps, than for butterflies and managed bees, but researchers argue that most farms don’t implement the types of habitat that are most valuable to wild bees. It’s also been shown that the plant species used to create pollinator habitat are preferred by honeybees and bumblebees, but rarely used by wild bees and wasps. To save our pollinators, we need to preserve their natural habitats and give them the room they need to recover.

To save our pollinators, we need to preserve their natural habitats and give them room to recover. Click To Tweet

Featured Image Credit: Shawn Caza

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