Ventura County agriculture officials plan to use their authority to eradicate a threat to the citrus industry.
Agriculture Commissioner Henry Gonzales said three breeding populations of Asian citrus psyllid have been detected in the county.
The bug can carry the fatal Huanglongbing disease.
The disease can ruin the color and the taste of citrus crops.
Gonzales said at least four commercial growers have refused to treat their crop regularly with pesticides.
At a meeting on Tuesday, he plans to warn those growers that he has the authority to treat their crops and send them the bill.
Treatment includes spraying the base of every tree at a cost of up to $400 an acre.
Spraying is recommended up to six times a year.
California's citrus industry is worth more than $1 billion a year.