A potential new threat to bumblebees identified by researchers

Parasitic worm sold to gardeners causes rapid death in bumble bees

A potential new threat to bumblebees has been identified by researchers at Liverpool John Moores University. Biological pest control products being sold to gardeners as a wildlife friendly pest control option can cause 80% of exposed bees to die within four days, according to this laboratory study.

Entomopathogenic nematodes are a type of parasitic worm which has evolved to kill insects, using bacteria released into the insect’s blood. These occur naturally in the wild but only at very low concentrations- but they are now sold for gardeners to apply at very high concentrations to control pest insects.

Dr Sally Williamson, LJMU Senior Lecturer in Neurobiology explained the findings, which were published in the online journal PeerJ:

"There is currently a great deal of concern about population declines in pollinating insects. Many potential threats have been identified which may adversely affect the behaviour and health of both honey bees and bumble bees: these include pesticide exposure, and parasites and pathogens.

"But our studies found that supposedly wildlife friendly biological pest control products sold online for use in gardens and organic farming are in fact potentially much more harmful to bumble bees than conventional pesticides. A major concern is that these biological agents can actually reproduce in the carcasses of dead bees, and therefore could potentially infect a whole bee colony or spread to the wider environment."

The researchers emphasise that neither the manufacturers and retailers, nor the people buying these biological pest control agents, are technically at fault: there is a loop-hole in the legislation regarding the regulation of pest control products containing parasites. Unlike chemical pesticides or microbes, parasites are actually animals, and their sale and use are only regulated for use in a country where they don’t occur naturally.

Dr Williamson, who has previously worked on the effects of chemical pesticides on bees, explains:

"As was the case with neonicotinoid pesticides, the legislation might need to be revised with regard to entomopathogenic nematode pest control products, if the effects we observe in the lab can also occur in the field- but much more research is needed before we can quantify this potential new threat in an ecological context."

A new threat to bees? Entomopathogenic nematodes used in biological pest control cause rapid mortality in Bombus terrestris. Alexandrea Dutka, Alison McNulty and Sally M. Williamson