STANDING AT THE CROSSROADS (Part II)
ADAPTIVE VARIETY SELECTION AND THE UNCERTAIN ROLE OF IMIDACLOPRIDS IN THE FUTURE OF SOUTHERN GRAPE CULTURE
By: R.L. Winters
Master Horticulturist/Ampelographer Fairhaven American Hybrid Research Foundation
[VT – Please welcome back VintageTexas guest blogger R.L. Winters in this three part blog on the impact of the use of imidacloprid pesticides our grape culture in Texas and the American Southland. Click here to read Part I – The MYSTERY.
NO WAY HOME
In the case of sublethal imidacloprid dosing, the pollinators aren’t killed directly, but absorb or transfer enough of the chemical to the brood to produce toxicity that overlaps into successive generations. In the process of unraveling this paradox, it has become clear that the neonicotinoid was being transferred back to the colony in the form of contaminated pollen. The pollen is then consumed and or conveyed to the developing larvae. As the larvae matured, the ingested tainted pollen delivers the sub-lethal dose that would manifest itself by damaging the foragers neurons to the degree that their ability to master the vital, million-year-old skills of colony behavior, was severely damaged.
As is detailed in the report published by Ecotoxicology 2012 May 21(4) 973-992; “Bees trained to forage on artificial feeders, Bortolotti et al. (2003) noticed that a 500 meter distance between the hive and the feeding area resulted in no foragers at the hive/feeding area up to 24 hours after treatment when foragers were fed with imidacloprid at 500 and 1,000 μg l−1. The latter authors also found that a lower concentration (100 μg l−1 imidacloprid) caused a delay in the returning time (to hive or feeding area) of the foragers”.
At the core of the mystery of the disappearance, the explanation seems to be a macabre set of symptoms that include the inability to navigate correctly.