With the warmth of summer comes the grueling task of yard work, but experts say people should be aware of how their planting, trimming, and spraying is affecting a quickly dwindling and vital population: bees.

“Without bees, the diversity in the food we eat would not get pollinated,” said Mary Harris, an Iowa State University adjunct assistant professor of natural resource ecology and management.

Without bees, many common fruits and vegetables would go extinct, including apples, strawberries, onions, and carrots.

Beginning as early as the 1970s, the honeybee population in the United States has been in decline, with some beekeepers reporting losses of up to 70 percent.

Many of the deaths are due to colony collapse disorder.

The disorder occurs when the majority of worker bees in a colony disappear and leave behind a queen and plenty of food.

Not all bee deaths are due to the disorder; however, the U.S. Agriculture Department reports that approximately one-third of all deaths are attributed to it.

Harris said many factors have caused the decline, but the two largest are loss of bee habitat and the use of insecticides.

Bee-friendly plants and flowers have been in decline lately, a critical factor, Harris said, which has not allowed them to properly find nectar the bees need to turn to honey and feed their young.

There are more than 25,000 species of bees in the world; 4,000 of those are native to the United States, and 200 are native to Iowa.

In Iowa, Harris said, the bee problem is only made worse with the high level of agriculture. Instead of planting bee friendly plants, many farmers plant corn and soybeans, which bees are unable to use.

Instead of seasonal crops such as corn, Harris said, bees need a variety of flowers that can last throughout the summer.

The bees are also losing their habitat because of urban growth, said Scott Black, the executive director of the Xerces Society for Invertebrate Conservation.

As communities grow, the concrete, as well as the turf laid by landscapers, is unusable by bees, which forces the hive to relocate, Black said.

Another big concern has been the use of insecticides, he said, with the most concerning insecticide being neonicotinoids.

What makes this insecticide particularly dangerous to bees, Black said, is the neonicotinoids are sprayed on the plants, and then absorbed, where they can live for a very long time.

Scientists are still not certain if there is a definitive link between neonicotinoids and colony collapse disorder. However, Harris said, there is growing evidence the insecticides have negative effects on honey bees.

Black said people need to be careful with all insecticides and only use them when they are absolutely necessary.

Wait till after pest issue has begun before using an insecticide, he said, instead of spraying as a preventive measure.

“We very rarely apply insecticides,” said Shawn Fitzpatrick, the supervisor of landscape services for the University of Iowa’s Facilities Management.

Fitzpatrick said pesticides can be split up into four different groups: herbicides, insecticides, fungicides, and rodenticides.

Appproximately 95 percent of all pesticides the landscape services uses are herbicides, he said.

The service only uses insecticides in the case of emergencies, and it hasn’t had to use insecticides in several years, he said.

However, the landscaping services also doesn’t plant many bee-friendly plants, Fitzpatrick said.  A small bee- and butterfly-friendly flower bed was installed near the east end of the Hancher foot bridge, but not much more has been done.

Black said helping bees is as simple as going outside and planting flowers they can pollinate.

“The neat thing about pollinators is anyone can take action,” he said. “Maybe not everyone can go across the globe to save polar bears, but everyone can plant flowers.”