The intended targets of neonicotinoid pesticides are aphids, which suck the sap out of plants and can spread viruses from plant to plant. These pesticides are also effective against harmful beetles, fleas, wood boring pests, flies, cockroaches and more.
These pests have natural enemies in the wild - for aphids, one of these is ladybugs. A new study from Penn State determined that these beneficial predators are also adversely affected by the presence of neonicotinoids. Negative effects include a population drop of 10 to 20 percent.
The researchers looked at more than 1,000 observations from field studies across North America and Europe, combining them to test the effect of seed-applied neonicotinoids on predatory insects. Neonics are applied to seeds, which are then planted, allowing the insecticide to enter the soil and plant roots. From there, the chemicals run through the plant to protect it from pests.
While the insect predator population decreased following neonicotinoid application, spiders, who dine on the same pests, were unaffected. This indicates that the population decrease is from the pesticide itself and not the decrease in food supply, which would equally affect both spiders and predatory insects.
The researchers recommended integrated pest management techniques rather than insecticidal seed coatings to control pests.