After routine testing last month showed an Ewa Beach basil farm was using the restricted pesticide methomyl, the Hawaii Department of Health conducted further sampling and found three more farms to be in violation.
"This flagged to us that there is a problem in our agricultural fields," said Deputy Director for Environmental Health Gary Gill. "Our farmers are using pesticides on basil, which are not allowed by law."
Although methomyl and other pesticides discovered by the recent testing are banned for use on basil by the U.S. Environmental Protection Agency, it's believed none of the tainted product reached local markets. All four farms were forced to destroy their crops in front of health inspectors.
"We took action, as we must by law, to restrict that crop (and) to prevent it from going to market," said Gill.
The four farms forced to plow over their basil crops, or cut plants down to the stalk, included Fat Law's Farm in Ewa Beach, Green Produce Farms and Luo's Plantation in Waianae, and S & Z Farm in Laie.
Methomyl is known to cause neurological, gastrointestinal and ocular problems in humans if ingested.
But according to Gill, the amount of pesticide found on Thai and sweet basil was so small, even if it reached grocery shelves or farmers' markets, there would be little threat to the public.
"It would probably be a neurological impact, but you would have to consume a whole lot of basil to have that impact," said Gill. "There's no anticipation of any kind of toxic reaction to the public."
The Hawaii Department of Health is working closely with the Department of Agriculture and the University of Hawaii College of Tropical Agriculture and Human Resources to educate farmers on the proper use of pesticides.
"We teach people how to use them correctly (and) how to use the label, so that they are reducing the risk to consumers," said Jim Hollyer, a farm food safety coach at CTAHR.
Thomas Matsuda, the Pesticides Branch chief for the Department of Agriculture, said many farmers make the mistake of matching a pesticide with the insect it's supposed to kill. Instead, farmers should check which crops the chemical can be used on.
"It's more important that the crop be on the label," said Matsuda. "You start with that."
Another barrier that could be preventing farmers from properly using pesticides is language. Some immigrant farmers in Hawaii may have a difficult time reading instructions in English.
"That is a barrier, so we are addressing that," said Matsuda.
CTAHR recently hired someone who speaks Mandarin to better communicate with farmers of Chinese ancestry. However, a woman who speaks Laotian recently retired and is no longer available.