<...any thought on why the neonic studies with negative results are so often done with canola/rape?>
One reason is that when studies were done on corn, the objections made to EPA by those who are concerned about pollinator exposure to neonicotinics, were that: 1) corn isn't necessarily attractive to bees, and 2) the primary routes of exposure during tassel time is from pollen. The one thing everyone could agree upon, exposure to neonictonics from planter dust was of concern. But, it's hard to control dust exposures, and beekeepers were complaining of general poor performance of colonies in the corn belt.
Based on our own honey bee studies over two years of 53 corn fields in IL, IN, and NE, during tassel time, we observed:
1) Corn pollen collection was a 'last' resort resource. If there was anything else available, the bees went for it. At many locations, bees collected little or no corn pollen.
2) Corn gutation droplets may be another exposure route, but we never saw this, and when I challenged this list to provide a photo of a bee collecting corn gutation droplets, no one did. If you can prove me wrong on this, please provide photographic evidence - I've yet to receive any.
3) Bees eagerly collect pollen from some varieties of sweet corn, but typically do not collect pollen from field corn.
We also sampled 30 canola fields distributed east, west, north, and south of Lethbridge. Due to complaints about basing decisions on corn studies, EPA encouraged studies on canola. Canola is attractive to bees. Seed canola fields are grown in isolated pockets to avoid drift of genetic materials - intentionally kept distant from canola grown for oil. As such, in places like western Canada, one can find large acreages of seed canola, all grown from treated seed. Canola also provides both nectar and pollen to bees. As such, the overall exposure should be much higher than from corn.
In simple terms, huge resources of attractive (canola) nectar and pollen grown from treated seed versus huge resources of unattractive (field corn) pollen grown from treated seed.
We observed:
1) Bee eagerly collected canola pollen and canola nectar,
2) Colonies at some fields collected only canola pollen, yet,
3) Most still collected pollen (and we suspect nectar) from a diverse array of plants in the habitats surrounding the canola fields.
In other words, they may not have had any real need for food resources other than canola, but they still elected to collect food from other resources. Once again, we are reminded of many older studies that indicate that bees thrive on a diversity of pollen and nectar sources.
In all cases, we used pollen traps to collect bee-collected pollen so that we could make slides for microscopic examination, assess the types and amounts of pollen being collected by the bees. And, we used satellite imagery to assess the kinds and amounts of habitats (fields and natural such as riparian zone, and in Canada, prairie) surrounding each sampled field. Sampled fields were a minimum of 1 mile apart, our goal was 3 miles or more, and in every study, we had groups of fields separated by 10s to as far as hundreds of miles (e.g, we covered IL from near the eastern border to the western border of the state).
We are in the final stages of completing a full Good Laboratory Practices audit of these three studies (IL/IN, NE, and Canada) and the Final Technical reports are going to EPA. Preliminary results have been provided to EPA all along, The full report for corn and the full report for canola are at the stage of final sign off by all study partners. I sent what I hope are the last GLP documents and signatures last week.
Jerry
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