“Neonicotinoids are the most widely used insecticides in the world,” according to Margaret Douglas, an entomologist at Penn State. Douglas is the co-author of a study of the ecological effect of the insecticides, often called “neonics” for short. Neonics are often applied to seed, including many types of genetically modified seed. The goal of the insecticide seed treatment is protect plants from early season pests, such as aphids.
Neonics have been implicated in the decline in bee populations. Another effect has just been identified—neonics actually help some organisms, specifically slugs and snails.
Douglas and her supervisor, Dr. Tooker, found that neonics are consumed by slugs and snails (as well as other organisms that live in the soil or on the soil surface). The insecticide doesn’t affect the molluscs themselves, but the chemical travels up the food chain. When slugs and snails are consumed by ground beetles, for example, the beetles are often killed. Spiders and beetles also absorb or consume the pesticide directly from the soil.
As a result, the neonics reduce the populations of natural predators, particularly spiders and beetles. Slugs and snails flourish. As for the crops, “out of the frying pan into the fire” applies—safety from aphids means an attack of the slugs.
Sources: Meta-analysis reveals that neonicotinoid seed treatments and pyrethroids have similar negative effects on abundance of arthropod natural enemies. M. R. Douglas and J. F. Tooker. PeerJ 4:e2776. 2016.
This insecticide lets more slugs eat crops. A'ndrea Elyse Messer, Penn State Agriculture. www.futurity.org. December 4, 2014
- Janet Wallace