A bee-safe pesticide based on spider venom
Protecting crops often means using synthetic chemical insecticides, sometimes with collateral damage to humans and other non-target animals. Even newer pesticides that are safe for mammals are killing helpful pollinators, like bees. But a new pesticide based on spider venom attacks the central nervous system of agricultural pests such as aphids and caterpillars without harming honeybees, a new study shows.
Proteins from spider venom, when combined with a carrier protein to transport the neurotoxin across the insect gut wall, will disrupt the calcium channels that allow ions into nerve cells, killing the bugs. Scientists have been developing such fusion protein insecticides for years. One example is Hv1a/GNA, which combines the calcium channel blocker found in the venom of the Australian funnel web spider (Hadronyche versuta) with a carrier protein derived from the snowdrop flower (Galanthus nivalis).
A team led by Angharad Gatehouse from Newcastle University wanted to see if this pesticide would harm beneficial bees. Calcium channels are linked to learning and memory in honeybees, who must learn and remember various floral traits to help them find food and return to their hives. So the team exposed honeybees (Apis mellifera mellifera) to varying doses: Some ate Hv1a/GNA in a sugary solution just once, while others ate massive amounts over the course of seven days.
Ingesting the biopesticide had only a slight effect on honeybee survival, and their larvae were similarly unaffected. Even when the researchers injected the pesticide directly into the bees, less than 17 percent died within two days. The team also conducted memory and learning tests, using a sweet treat to train bees to extend their long mouthparts (or proboscises) when stimulated by a floral scent. Bees exposed to the fusion protein performed the same on these tests as the no-pesticide control bees.
The findings suggest that this bee-benign biopesticide doesn’t block the calcium channels in honeybees, likely because of differences in the channel receptors between bug species. And that’s some good news to take back to the hive. — Janet Fang | 5 June 2014
Source: Nakasu, E.Y.T. et al. Novel biopesticide based on a spider venom peptide shows no adverse effects on honeybees, Proceedings of the Royal Society B (2014). doi: 10.1098/rspb.2014.0619
Image: bee with snowdrop by Petrikov Denis | shutterstock.com
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