WASHINGTON (AP) - Two studies suggest a common type of pesticide is causing problems for honeybees and bumblebees, important species already in trouble.
    
The new research suggests the farm chemicals reduce the weight and number of queens in bumblebee hives and that they cause more honeybees to become disoriented and fail to return to their hives.
    
Just last week activists petitioned the government to ban the pesticide, which one producer says is used on 90 percent of the corn grown in the U.S. 

But some scientists say the new research pointing to the chemicals isn't convincing.
    
The studies are published online Thursday in the journal Science.

Bees are needed to pollinate fruit, vegetables and nuts. Without them experts say our diets would be bland.