GOLDEN GATE BRIDGE -- Bay Area groups that oppose the spraying of their cities to eradicate the light brown apple moth marched on the Golden Gate Bridge Saturday to help spread awareness of what they say are ineffective and unsafe chemicals.

San Francisco and Marin County conglomerates of anti-spray groups began on either end of the bridge beginning at 10 a.m., met near the middle and then marched to San Francisco together, according to Mothers of Marin Against the Spray Chair Lisa Krausz.

She said the crowd spread across the bridge from end to end and estimated that 400 to 500 marchers were in attendance.

"It was beautiful; it was a beautiful thing," said Krausz.

The crowd then headed over to Crissy Field for a noon rally with a number of speakers and live music.

Among the scheduled speakers were KGO health and fitness expert Joanie Greggains, Sen. Carole Migden, D-San Francisco/North Bay and state Assemblyman Mark Leno, D-San Francisco.

Representatives from the California Alliance to Stop the Spray, Stop the Spray East Bay, Don't Spray San Mateo and Stop the Spray Sonoma were also scheduled to speak at the rally.

The California Department of Food and Agriculture today released a statement in reaction to the march, defending the spraying.

"We would like to take this opportunity to remind the citizens of the Bay Area that aerial treatment with moth pheromone to eradicate the light brown apple moth is a time-tested approach that has been utilized successfully around the world for more than a decade," the department stated.

Dr. Anne Haiden, another speaker scheduled for the protest today, is an integrative functional medical specialist who released a study Thursday that found that more information is needed on the spray used to eradicate the moths.

Haiden said her research found the chemical being sprayed, a pheromone, could adversely affect people's respiratory and endocrine systems.

The California Department of Food and Agriculture has been spraying the synthetic pheromone as part of a statewide campaign to wipe out the moth, which feeds on more than 250 agricultural crops and 2,000 types of plants and trees.

Krausz says the anti-spraying groups believe that state data, which claims that the moth is a threat to California agriculture, is unconvincing and that it has not been proven that the spray will eradicate the pest.

"We are trying to raise public awareness, voice our strong opposition and get people aware of the issue," she said. "Especially of the information, the science that counters what the state is telling us."

In its statement, the department said it would not resume the spraying until independent laboratories conducted tests on the pheromones used in the spray to ensure there would be no adverse health effects.