This is an interesting study about the impact of pyrethroid pesticides on honeybee fertility. Rather than just flat wiping out bees, these supposedly green pesticides are slowly destroying the queen laying numbers and egg success. So you can soak the bees in the chemical and it is fine, but the real impact is on laying. Beekeepers who have witnesssed the much higher failure rate of queens these days will be especially interested.

"After first establishing the dose that would kill no more than five percent of exposed bees, the researchers laced sugar water near bee hives with either of the pyrethroids at that tolerable dose. Worker bees had access for 20 days to the pseudo-nectar in each of three successive years. Queens in each colony were dosed every five days over each treatment period. Studied bees had no access to outside nectar during the trial periods.

Compared to queens receiving clean sugar water, those in the pyrethroid groups were substantially less fecund. For instance, clean queens in 2006 laid a little more than 1,200 eggs each day, compared to not quite 900 a day in the bifenthrin group and roughly 600 per day in the deltamethrin group. In general, the weight of eggs laid was higher in the pyrethroid-treated hives, but the hatch rate of pyrethroid-exposed eggs was significantly depressed. It varied by year, but in 2008, for instance, 88 percent of eggs in the control hives hatched versus 71.4 percent of those in the bifenthrin-treated hives and 80.5 percent of the deltamethrin-treated bees.

The success rate of hatchlings, that is the share that reached adulthood, varied from 75 to 95 percent in the control hive – making it between 20 and 40 percentage points higher than in hives where bees had been exposed to a pyrethroid. Dai and colleagues report their findings in the March Environmental Toxicology & Chemistry.

The bottom line, Dai’s team concludes: “The impact of pesticides on the colony may be severe.” "

Interesting the study is from China, where the beekeeping industry is no stranger to chemicals...


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