Madera County, Calif., grower Philip Hagopian told GrapeLine he had crews walking his Thompson seedless vineyards dusting with sulfur or clipping off bunches trying to head off botrytis ahead of harvest.

Hagopian’s flood-irrigated vineyards include 250 acres of Thompsons, which he grows for raisins, as well as small blocks of wine grapes — Black Muscat and Riesling — and Flame Seedless and Red Globe table grapes.

Earlier in the season, about a third of Hagopian’s Thompson acreage suffered heavy pressure from powdery mildew in parts of three of his four raisin grape blocks. Cracks or splits in the infected berries left the grapes vulnerable to entry of the botrytisorganisms.

Hagopian first noticed botrytis decay in his grapes at mid-August, particularly in areas along pipelines and at row ends where water accumulates.

“We’ve been checking the areas where we had problems with powdery mildew for any signs of rot,” he says. “We’re not finding too much, but where we do, we want to get it out.

“Mildew overwintered in some of our fields. That, coupled with weather conditions conducive to growth of mildew, made it really tough to control the disease in those areas,” he told GrapeLine.

You can read more about what Hapogian had to say about his 2011 crop by visiting back issues of GrapeLine at where you can also subscribe to future, exclusive in depth issues. Mailed twice monthly through September, the e-newsletter is sponsored by Chemtura AgroSolutions.