The wine grape and raisin harvest on 2,700 acres of San Joaquin Valley vineyards was halted because of repeated cases of field worker poisonings involving the pesticide Zolone. County agriculture commissioners from Kern County in the south to San Joaquin County in the north alerted growers to halt the harvest in fields that may have been sprayed with the pesticide. Zolone, used to control leaf hoppers in vineyards, has been in use for 18 years. State Department of Food and Agriculture spokesman Jim Wells said he believes that the harvest had been 50% to 60% completed in the fields where spraying had occurred. He said it is unlikely that the ban will be lifted before completion of the harvest season. Most of the 79 workers affected suffered nausea, vomiting, stomach cramps, headaches. Wells said the state will consider, on a case-by-case basis, allowing machine harvesting in the suspected fields or hand harvesting under medical supervision.