I've never noticed a lack of drones post-canola personally, nor have I ever heard my neigbours who move their bees south for canola pollination mention a lack of drones post-canola (I'm in central Alberta). 

Having said that, it's possible we're missing it because the effect would be seen so late in the season we're assuming it's the natural population cycle of drones in the hive. 

In a field setting, drones fed on canola pollen would be laid sometime mid- July to early August, when the canola is blooming. So they'd be hatching  in August, and then, IF this study were accurate, be dead by late August or early September. 

This mirrors the natural population cycle. Most of the drones are laid much earlier in the season, in May and June. The colonies have already cut back drone laying by July. I would suspect, even if we were losing drones to thiamethoxam, it would be happening so late in the year we would be assuming it's natural end-of-season changes in their population. I certainly see far fewer drones on August 25th than I do on June 25th. 

It's also hard to say because the time before canola and thiamethoxam was so long ago and canola is so ubiquitous today. What we think is a normal, natural dearth of drones in late August and early September may not be. But in general, the overwintering success of hives around here is pretty good, so I would say the effects, if any, aren't having a noticeable impact on the hives nor the industry. 

However, I can't rule out impacts in odd years because every once in a while things "go funny."  There have been plenty of beekeepers complaining about failed late-season supercedure attempts the last couple of years. 

Tracey

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