Synthetic pesticides don’t belong on organic produce.

But studies published in Consumer Reports and academic journals show that conventional pesticides occasionally end up on organic salad greens or apple skins, due to past soil contamination, drift from neighboring farms or actions of unscrupulous operators.

The Organic Foods Production Act – the cornerstone of U.S. organic law – requires regular testing of farms for pesticide residue, adding an extra layer of protection for consumers.

Though seven years have passed since organic regulations first took effect, pesticide-residue testing still is almost never done.

In fact, according to Miles McEvoy, a top federal organic official, only one of 100 government-accredited organic certifiers conducts regular testing, taking annual samples from just 5 percent of the farms it inspects.

That unfulfilled mandate illustrates what the Organic Consumers Association, National Organic Coalition and other groups say is a lack of action by the U.S. Department of Agriculture’s National Organic Program, creating a chasm between consumer expectations and actual industry practices.

Organic program leaders say a small staff and limited funding – the NOP’s 2009 budget was $3.87 million – have hampered its ability to adopt much-needed changes to organic regulations, and punish operations in violation.

But Nancy Ostiguy, a former member of the National Organic Standards Board, which recommends changes to organic rules, said the USDA’s “not-so-benign neglect” and conflicted mission contribute to the organic program’s shortcomings.

“The USDA was – and to a large extent, still is – the wolf watching the chicken house,” said Ostiguy, a Penn State University entomology professor. “It has this dual role of both promoting agriculture and protecting the public against poor agriculture practices. It has this difficulty with which hat it is supposed to be wearing, when.”

Others, including the Cornucopia Institute, an organic watchdog group, blame USDA inaction on a pro-big-business political philosophy and a reluctance to put the brakes on the $23 billion U.S. organic-food industry.