Bud dissecting information foretells average grape crop

Conventional coffee shop wisdom would suggest the hard, cold winter California has just experienced, coupled with a relatively small grape crop last season, would foretell an unwanted large grape crop this year.

Not necessarily.

Bud dissection information from one of the largest labs in the state and a major raisin packer suggest the 2007 grape crop now in bud break is not that big. Average or maybe a little below is the crop size estimate at this very early stage of the game.

Devin Carroll, Bio Ag Services, Fresno, Calif., one of the leading bud dissectors in the state, has been offering bud dissection services for 19 years, currently analyzing about 16,000 buds per year.

“This year looks pretty close to average across the state,” he says. “We’ve seen a few buds that appeared to be damaged by the frost, but I don't think it will be a big deal.”

According to sources, bud dissection by a major raisin packer is showing that Thompson seedless is running about 75 percent to 85 percent of normal fruitfulness for the upcoming season, slightly better than in 2006.

Bud dissection analysis can provide two types of information, says Stephen Vasquez, UC Cooperative Extension farm advisor in Fresno County and Matthew Fidelibus, UC Cooperative Extension viticulture specialist at UC Kearney Agricultural Center, Parlier, Calif.

It can be used to estimate cluster counts, and gives growers some insight on bud health in specific blocks and whether bud mortality is affecting yields.

However, bud fruitfulness is only one parameter affecting the final yield; other critical variables include percent bud break, cluster size, berry set and size, and soluble solids.

A good example of the one-parameter aspect of bud dissection is that bud dissection did not reflect the huge 2005 grape crop.

Nevertheless, bud dissection is catching on as an analytical tool for predicting yield, discerning necrosis and planning for pruning. “It’s certainly catching on with the 'cutting edge' crowd,” says Carroll. “It’s an inexact science at best, but still a fairly good indicator of yield from year to year.”

In addition to yield potential, Carroll tabulates necrosis and quantifies his findings in three stages — sick, dead, and burnt.

Interest in bud dissection and how valuable it is to the grower has evolved over the years.

“Bud dissecting is not too common in raisin production because both the investment and the return are lower,” he says. “At one time we had more table grape business. In the past 3-4 years, our growth has been mainly with wine growers in high value districts such as Sonoma, Napa, and Lodi.

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