Lu et al. (2012) reported they were able to replicate [Colony Collapse Disorder] with sub-lethal doses of imidacloprid. The imidacloprid-treated hives were nearly empty, consistent with CCD, and the authors exclude Varroa or Nosema as contributing causes.[10]
In May 2012, researchers at the University of San Diego released a study showing that honey bees treated with a small dose of imidacloprid, comparable to what they would receive in nectar and formerly considered a safe amount, became "picky eaters," refusing nectars of lower sweetness and preferring to feed only on sweeter nectar. It was also found that bees exposed to imidacloprid performed the "waggle dance," the movements that bees use to inform hive mates of the location of foraging plants, at a lower rate.[36]
Researchers from the Canadian Forest Service showed that imidacloprid used on trees at realistic field concentrations decreases leaf litter breakdown owing to adverse sublethal effects on non-target terrestrial invertebrates. The study did not find significant indication that the invertebrates, which normally decompose leaf litter, preferred uncontaminated leaves, and concluded that the invertebrates could not detect the imidacloprid.[37]
A 2012 in situ study provided strong evidence that exposure to sublethal levels of imidacloprid in high fructose corn syrup (HFCS) used to feed honey bees when forage is not available causes bees to exhibit symptoms consistent to CCD 23 weeks post imidacloprid dosing. The researchers suggested that "the observed delayed mortality in honey bees caused by imidacloprid in HFCS is a novel and plausible mechanism for CCD, and should be validated in future studies".[38][39]