The Poisoning of Bees on Sunflower Crops

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Marietjie at Boshoff Apiaries asks:

Do you have any info regarding the poisoning of bees on sunflower crops?

Rusty Burlew replies:

Although sunflowers can produce small crops of seed without the help of bees, bees greatly increase seed set, leading to higher yields per flower. In addition, bees are critical for hybrid seed production, which requires cross-pollination between varieties.  Bees are happy to comply because they get both nectar and pollen from the flowers. Many types of bees can do this work, including honey bees, bumble bees, and some native bees. I have never heard of sunflowers harming bees in any way. In fact, research shows that sunflower pollen helps to control certain pathogens that live inside bee digestive systems. Sunflower pollen can reduce the infection rate of Crithidia in bumble bees and Vairamorpha (Nosema) in honey bees. Poisoning of bees in sunflowers could be a result of insecticides used on the crop, especially systemic ones. If a highly toxic pesticide is applied incorrectly or at the wrong time, it could damage bees. Also, some pesticides travel on airborne particles and could be blown onto a crop of sunflowers. Clouds of toxic dust have killed thousands of pollinators, especially when the dust is stirred up by cultivating and harvesting equipment. In a situation like this with many unknowns, a laboratory examination of dead bees would be a good first step.