Don’t do that, honey

Field tests show how pes­ti­cides can wreak havoc on hon­ey­bees.

The Star Malaysia - Star2 - - Science - By MIRA ABED

HU­MANS are big fans of bees. We rely on them to pol­li­nate crops like al­monds, wa­ter­mel­ons and ap­ples.

But bees prob­a­bly aren’t big fans of hu­mans – at least, not of our agri­cul­tural prac­tices.

In par­tic­u­lar, they ought to be of­fended by our fond­ness for a widely used class of pes­ti­cides called neon­i­coti­noids (neon­ics, for short).

Stud­ies in the lab have shown that some doses of neon­ics are out­right lethal to many bees and that even sub­lethal doses can shorten a colony’s life­span and harm its over­all health.

Re­sults have been sim­i­lar in small-scale field stud­ies.

Still, ex­actly how these pes­ti­cides, which are ap­plied to seeds be­fore plant­ing, would af­fect bees in the real world re­mains some­thing of a mys­tery.

Sci­en­tists have been locked in a fierce de­bate over how much – and for how long – bees en­counter these pes­ti­cides in their daily lives. Af­ter all, the con­di­tions in a field are far more com­plex than those in a lab.

Now, two stud­ies pub­lished side by side in the jour­nal Sci­ence at­tempt to an­swer this con­tentious ques­tion.

One of the stud­ies was con­ducted in Canada. It com­bined large-scale field work and lab­o­ra­tory ex­per­i­ments to bet­ter un­der­stand real-world neonic ex­po­sure lev­els and their ef­fects on hon­ey­bees.

The other was con­ducted in large fields in Hun­gary, Ger­many and the UK. Its goal was to un­der­stand how the ef­fects of neon­ics vary be­tween coun­tries and how ex­po­sure dur­ing the flow­er­ing sea­son af­fects the long-term health of a bee colony.

The re­search, pub­lished re­cently, pro­vides a lot of new in­for­ma­tion and poses still more ques­tions. Here are some of the key take­aways:

Bees are ex­posed to neon­i­coti­noids for longer than we thought

In the Cana­dian study, bi­ol­o­gist Amro Zayed and his team at York Univer­sity in Toronto mon­i­tored 55 honey­bee colonies in 11 lo­ca­tions from May through Septem­ber 2014, a longer time than pre­vi­ously mea­sured.

They found that hon­ey­bees placed near corn­fields planted with neonic-coated seeds were ex­posed to de­tectable lev­els of neon­i­coti­noids for three to four months.

Even some of the bees placed far away from agri­cul­tural crops were ex­posed for around one month as the pes­ti­cide moved through the ecosys­tem. (More on that in a bit).

In the Eu­ro­pean study, a team led by Ben Wood­cock and Richard Py­well from the Cen­tre for Ecol­ogy and Hy­drol­ogy in Eng­land stud­ied bees in 33 sites, each split into ar­eas that were treated with pes­ti­cides and ar­eas that weren’t.

They found that bees were ex­posed to neon­ics even in the un­treated fields. This was par­tic­u­larly sur­pris­ing con­sid­er­ing that the chem­i­cals have been re­stricted in Eu­rope since 2014.

The re­searchers said this in­di­cates that the pes­ti­cides re­main in the en­vi­ron­ment long af­ter a treated crop has been har­vested.

Real-world doses of neon­i­coti­noids are bad for bees

In gen­eral, both stud­ies showed that the con­cen­tra­tions of neon­i­coti­noids that bees ac­tu­ally en­counter in fields are in­deed dan­ger­ous for bees.

Wood­cock’s team found that, in Hun­gary and the UK, the more neon­i­coti­noids there were in the ecosys­tem, the smaller the size of the honey­bee colonies and the lower the fer­til­ity rate of wild bees.

Zayed and his team showed that worker hon­ey­bees died around five days sooner when ex­posed to neon­ics. That amounted to a 23% de­crease in life­span.

Ex­posed worker bees also dis­played dif­fer­ent be­hav­iour than un­ex­posed bees. They tended to fly far­ther from the hive, as if they were lost.

That symp­tom has been seen in pre­vi­ous stud­ies.

The worker bees also were slower to recog­nise and re­move dead or dy­ing bees from the hive. This is im­por­tant be­cause re­moval keeps colonies healthy by elim­i­nat­ing po­ten­tial sources of dis­ease, Zayed said.

Per­haps most dev­as­tat­ing, ex­posed honey­bee colonies had dif­fi­culty keep­ing a lay­ing queen.

This can be cat­a­strophic be­cause if a re­place­ment queen is not raised within three days of the pre­vi­ous queen’s death, no new eggs can be pro­duced, and the colony will quickly die.

Be­tween 70% and 80% of Zayed’s ex­posed colonies would have died with­out out­side help, he said.

Neonic ex­po­sure can come from un­treated plants

In both stud­ies, neon­i­coti­noids were found in un­treated ar­eas and plants.

Zayed’s group found that most of the con­tam­i­nated pollen col­lected by Cana­dian hon­ey­bees ac­tu­ally was from un­treated wild­flow­ers, not from treated corn or soy.

While sci­en­tists don’t know how neon­i­coti­noids spread in the en­vi­ron­ment, there are sev­eral plau­si­ble ex­pla­na­tions.

Since these pes­ti­cides can dis­solve in wa­ter, it is likely that dis­per­sal oc­curs when neonic-con­tam­i­nated wa­ter is sucked up by other plants, Zayed said.

Richard Shore and Py­well, both re­searchers from the Cen­tre for Ecol­ogy and Hy­drol­ogy, said that wa­ter, soil and dust are all pos­si­ble ways neon­ics might spread.

En­vi­ron­ment mat­ters – and it’s re­ally, re­ally com­pli­cated

One of the big­gest mes­sages from the Eu­ro­pean study is that the real world is in­cred­i­bly com­plex, said Maj Rundlof, who stud­ies bees at the Univer­sity of Cal­i­for­nia, Davis and Lund Univer­sity and was not in­volved in ei­ther of the new stud­ies.

The vari­a­tion is so great, both within and be­tween coun­tries, she said, that there must be a wide va­ri­ety of fac­tors at play.

One is the par­tic­u­lar com­bi­na­tion of agro­chem­i­cals to which bees are ex­posed. Farm­land may be treated with pes­ti­cides, her­bi­cides, fungi­cides and more. Just as some med­i­ca­tions can in­ter­act with oth­ers, Zayed said, agro­chem­i­cals can join forces to in­ten­sify harm to bees.

Zayed’s team an­a­lysed the tox­i­c­ity ef­fects of the two most com­mon com­bi­na­tions found in their field tests.

In one case, the re­sults were star­tling: When the neon­i­coti­noid thi­amethoxam was com­bined with the fungi­cide boscalid, the neonic be­came twice as toxic to hon­ey­bees.

Ad­di­tion­ally, the Wood­cock team found that neon­ics had dif­fer­ent ef­fects in dif­fer­ent coun­tries.

The pes­ti­cides did the least dam­age in Ger­many, and the team has a num­ber of ideas as to why.

The Ger­man bee colonies were much health­ier over­all, with fewer in­stances of dis­ease and par­a­sites. They also had dif­fer­ent di­ets, con­sist­ing of only about 15% neonic-treated rape­seed; in Hun­gary and the UK, by con­trast, rape­seed ac­counts for 40% to 50% of the diet.

This doesn’t nec­es­sar­ily mean we should ban neon­i­coti­noids

The study au­thors and mul­ti­ple other ex­perts said it would be pre­ma­ture to ban neon­i­coti­noids.

Nor­man Car­reck, who re­searches bees at the Univer­sity of Sus­sex and did not work on the new stud­ies, said the EU’s 2014 mora­to­rium on neon­ics has led to pest prob­lems in Eng­land.

The mora­to­rium forced farm­ers to use al­ter­na­tive pes­ti­cides, and their ef­fects on bees are mostly un­known.

“Farm­ers do an im­por­tant job,” Zayed said. In mak­ing a de­ci­sion about neon­i­coti­noid use, we need to find a so­lu­tion that “would re­duce the cost to pol­li­na­tors but at the same time still al­low farm­ers to pro­duce an eco­nom­i­cally vi­able crop”. – Los An­ge­les Times/Tri­bune News Ser­vice

Stud­ies have shown that some doses of a class of pes­ti­cides called neon­i­coti­noids are out­right lethal to many bees and that even sub-lethal doses can shorten a colony’s life­span. — TNS

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