Stress kills bees, but it's very hard to measure

The typical measure of pesticide potency is the Lethal Dose 50 (LD50). Designed in 1927 (at the same time as the Ford model A ) it measures the amount of a material, given all at once, which causes the death of 50% of a group of test animals. It helps cross compare potency between chemicals, and if you read studies on neonicotinoid pesticides you'll find it is a very common measure.

LD50 fails to measure the impairment of bee skills and the interaction between stresses. For example, forager navigation impairment due to pesticides and a harsh winter will kill the whole colony through starvation long after the summer foragers have died. There are so many vital bee skills: nursing, guarding, cleaning, mating and hidden bonds and connections to ecology, that science is at a total loss to measure. New research shows what every beekeeper knows; a dose of pesticide does not need to be lethal in the LD50 or even a fictional LD1 test sense to be lethal to a colony and stresses combine:

 “This can explain why finding the link between colony failures and a single specific stress factor has so far proved elusive,” John Bryden, a biologist at the Royal Holloway University of London and co-author of the report.

It's not just pesticides which stress bees - regularly opening hives stresses bees. I know many wild colonies of bees in the UK which have flourished for 10+ years. According the National Bee Unit you must treat your bees with chemicals for mites and inspect regularly or they will die in 3 years. However once established, wild bees seem to cope with varroa mites, disease and weather. Regularly opening hives breaks hidden bonds.

Like the Model Ford A, the LD50 test should be retired from service and beekeepers need to think carefully how they might be contributing to stress.

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