When it comes to harvesting wine grapes, Stanislaus County vintner John Monnich likes the fruit to hang on the vines as long as needed to achieve the best flavors and smoothest tannins for his wines.

As things looked in early September, he’s expecting his red grape varieties will have plenty of hang time this season.

Monnich, a board member of the San Joaquin Valley Wine Grape Growers Association, and his wife, Judie, own Silkwood Wines, Modesto, Calif. They crush their grapes – Alicante Bouschet, Cabernet Sauvignon, Petite Sirah and Syrah – from vineyards in the Tuolumne River and Dry Creek areas of Stanislaus County.

“We want our wines to be mature, mature and mature,” John says. “Our climate here in the San Joaquin Valley contributes to that by allowing time for the grapes to mature naturally with little concern for rain.”

With his red grapes continuing to ripen for an expected start of harvest in late September, John likes what he’s seeing.

“The fruit is in good condition, with lots of tannins,” he says. “And, it looks to be quite turgid – not soft, but very firm and tight. That’s a good sign that we’ll be able to carry the crop for another three to four weeks to maturity; however, the seeds are still green.

At the first of September, sugar levels of his red varieties were in the range of 22 to 24 ºBrix, except for one block of Petite Sirah, which registered 25 ºBrix

“We like to harvest that variety at 24 to 26 ºBrix, so we’ll try to keep the Petite at 25 ºBrix for a few weeks and watch for any shriveling of the fruit and adjusting the irrigation as needed,” John says.

He anticipates yields this year will fall a little below average, but not as much as they did the last two seasons. That’s when water shortages cut yields each year by about 11 percent below average.

Meanwhile, he looks for quality of the grapes to be up this year.

“As long as we get the hang time we want, we’ll have good grapes,” John says, “The juice is going to be much better in the vineyard this year. The key is to let the fruit hang until it’s ripe and then put it in tight grain oak wood for 4 to 5 years. With warm-climate grapes, that’s the key to making better quality wine. We released a Petite Sirah several months ago after it had been in French Oak barrels for eight years.”

Puncturevine, a recurring threat, has been more prevalent in the vineyards than usual this year. Over the years, the puncturevine weevil has proven successful in keeping this summer annual weed at bay. Two species are released in July in areas where the weed is a problem. One attacks the puncturevine seed, the other attacks the stem.

“The puncturevine weevil has worked well for us,” John says. “Its only food source is puncture vine. So, once these weeds die out, so do the weevils. At one time we were involved with 540 acres of grapes with areas of puncturevine that I treated with the puncturevine weevil. Now, the weed is no longer a problem there.”

This year, pressure from powdery mildew, the main disease concern, has been lower than usual. To reduce the on-going threat from this fungal disease, John is working with a drone manufacturer to develop sensors that will detect the fungal spores in the air before the vines show symptoms of the disease.

He is also testing a tractor-drawn machine, made by Agrothermal Systems, that blows air, heated to 300º to 350^o F., through the canopy to reduce humidity levels and spore numbers. “This treatment is designed to lower powdery mildew pressure on the vines while also killing soft-bodied insect pests and encouraging genome expression of the fruit to improve the wine’s sensory characteristics,” John says.