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What’s the BUZZ with bees?

By Staff | Jan 20, 2020

-Photo submitted by Amy Toth Honey bees in hives placed near flowering prairies in late summer and early fall were much healthier than those left near soybean fields after August, the researchers found. Pictured here are study co-author Ashley St. Clair (at hives), and Zoe Pritchard, 2018 ISU graduate in biology and environmental studies.



During a recent Iowa Learning Farms’ webinar, Randall Cass, Iowa State University Extension entomologist, gave an overview of some of the research that is being conducted in Iowa with bees, including the implications for farmers, beekeepers and landowners.

Cass said oftentimes, people are surprised to find out there are several hundred species of bees in Iowa.

“I ask people if they know how many species of bees we have in Iowa. They can think of bumblebees, honeybees and of course, some people mention sweat bees. Other than that, people aren’t quite sure,” he said. “We have between 300 and 400 species here in Iowa alone and thousands across North America. It’s important people are talking about these. Honeybees are just one species of bee that is out there.”

Cass said populations of both honeybees and native species of bees are on the decline.

So what can people do about it?

“With honeybees, we have some management techniques we can use in order to keep their populations up,” he said. “But with native species, we don’t have those tools. Finding bees we haven’t seen in years is important. Even in our own backyard we have a bee that is on the endangered species list.”

That bee, Cass said is the rusty patched bumble bee that is native to Iowa. Looking for them and other bees can help with research.

“If you have a good eye and like to take photos of insects you can report sightings of bees,” he said. “If you do end up seeing the rusty patched bumble bee, you can send photos to Bumble Bee Watch and help them get a good idea of where these species can still be found.”

Bumble Bee Watch is a citizen science project dedicated to tracking and conserving North America’s bumble bees.

Honey bees and native bees

Cass said there has been some concern that honeybees and native bees may compete for resources.

“That’s another important factor to highlight when noting that honeybees aren’t native to North America,” he said. “They tend to be more generalist they are willing to forage on a variety of flowers for nectar and pollen, whereas a lot of native species tend to be more specialist they have a specific symbiotic relationship with native flowers.”

And obviously, Iowa’s landscape is not what it used to be.

“When we look at the Iowa landscape, it’s dominated mostly by annual crop production,” he said. “When we compare Iowa to the rest of the U.S., the U.S. has about 40 percent of the land area is dominated by farms. In Iowa, it is more than twice that average with about 85 percent of the land being devoted for agricultural production.”

What does that mean for our bees?

“It means a few things and it’s not all good news,” he said. “It means there is a limited forage availability for the bees. When we take land and turn it into agricultural production, it limits the amount of flowering plants that could provide resources for the bees.”

And, then there’s winter.

“A lot of keepers find they lose hives during the winter for their honey bees,” he said. “It’s either caused by the fluctuations of temperatures or the bees just aren’t able to make it all the way through the winter with the resources they were able to collect during the season. Overall, it can be a challenging landscape for the honeybees.”


When we talk about the challenges that bees face, we tend to focus on three primary stressors:

1. Pesticide exposure.

“That goes without saying that in Iowa, with 85 percent of our land devoted to agriculture, pesticide exposure is something that can affect bees whether that is treated seeds and that systemic insecticide is taken up by the plant and when bees visit it, there’s trace amounts of insecticide in the nectar or pollen they are collecting. Or, it could also be foliar sprays of pesticides or aerial sprays that could be affecting the bees that are living inside the cropland or around cropland edges,” said Cass.

2. Poor forage availability.

“Since 85 percent of our land is in row crops, that limits the amount of flowering plants we have around for our bees,” he said. “Flowering plants are what bees rely on for nectar and pollen resources. It’s their food. Their bread and butter. Without flowering plants there’s no food for the bees to eat off of and if the bees are starving then they are not going to fair very well.”

3. Pests and pathogens.

Cass said Varroa mite is probably the greatest challenge being faced by beekeepers today.

“This parasite lives on the backs of bees,” he said. “It can jump from bee to bee and spread different viruses between them. Beekeepers seem to be most concerned about Varroa mite more so than about insecticides.”


Cass said recent research has been focused on mainly pesticide exposure and forage availability.

In areas of high cultivation, where there is a lot of agriculture present, Cass said hives tended to be heavier.

“That was quite surprising,” he said.

However, despite hive placement in those areas of high cultivation, the hives tended to lose weight towards the end of the season.

“Starting around September and October, hives start to lose weight,” he said. “That means the bees are feeding on all of the resources they have stored up and they are less equipped for going into the winter. In order to survive the winter, they are going to need some food sources.”

In order to help find answers to the questions as to how to maintain hive mass, Cass said they devised an experiment where all of the hives were placed in the middle of a soybean field, which is considered a high cultivation landscape. When the soybeans were done blooming, they moved half of the hives to a prairie.

Cass said the hives that stayed in the soybean field continued to lose weight, whereas the hives that were moved to the prairie site gained a little weight.

“They were given a little boost,” he said. “That’s promising data.”

Next, Cass said they designed a longer study. This particular research project was three years of fieldwork that just came to an end this fall.

In order to increase replications, he said they increased the number of sites and hives and they also wanted to take into account insecticide exposure and look at more specific landscapes.

What have they seen so far?

In terms of insecticide treatment on soybeans, Cass said they have not seen it affect hive mass.

“It doesn’t mean that it’s not having an affect on the hives, but for example, we didn’t see massive die offs, even when hives were placed in fields where there was a pyrethroid spray occurring,” he said. “What this means is, there could be some sub lethal affects that it is having on the hives overall.”

Some of the additional research looked at queen health.

“We were able to see in some incidences, the hives that were placed in conventional sites and the hives that were exposed to insecticide sprays, we saw the queens laying less eggs even after being moved to prairie,” he said. “On hives that weren’t treated with insecticides, moving them to prairie caused the queen to increase the number of eggs she was laying. If that queen was in an insecticide treated hive, she never fully recovered. Data seems to be trending that, although it doesn’t affect overall hive mass, insecticide treatment could have some sub lethal affects on hives.”

Cass said the research is ongoing.

“There is promising data about site selection and how well our hives can thrive,” he said. “There is no significant difference on insecticide treatment, at this point, that we can see with our indicators, but that just means there is more opportunities to look at some of the smaller, sub lethal effects that are happening inside of the hive as a result of insecticide treatments.”

Another part of the research was polling farmers asking them how important they feel pollinator-friendly practices are.

“I was surprised to see that all of the farmers that I have surveyed, so far, say it is very important or somewhat important,” he said. “None of them said it wasn’t important at all. So, that means, this is an area that folks are interested in. Regardless of preconceived notions or what you think people would say. Pollinator-friendly practices and pollinator conservation is something that people are interested in.”

What can you do to attract native bees?

Cass said there are some practices people can do in their own backyard to help attract all beneficial insects in general.

“You need to consider timing of flowering, for bees probably the most crucial parts of the year for floral resources for them are early spring and late fall,” he said.

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