The impact of machine harvesting grapes on the quality of the finished wine is not something that everyone can agree on. There are many in-depth studies investigating the effects of machine harvesting, and like with most studies, the results vary.
There are new and improved grape harvesting machines that can be programmed to accommodate most winemaker's preferences. They can easily be adjusted and pick grapes just as clean as any hand, not to mention harvesting a large area with a lot less time.
It is also works out cheaper per hectare to use machine harvesting as well. Some winemakers argue that their premium quality wines require careful treatment, sticking with the tradition of hand picking.

 

For many vineyards, a dwindling labour force has been a main reason for using machinery. But for others, skepticism takes over raising the argument that there's no opportunity to do selective harvesting, or instruct the machine to leave the second crop, or skip bunches with rot and mold.
Machine harvesting substantially brings down the cost of getting the grapes from the vineyard to the winery. The exact saving depends on a number of factors, but approx 60% savings are an average result. However, does this practice lower the quality of the grapes and the finished wine? The ill-informed purist would say yes (as most of the great vineyards of the world are harvested by hand), but the evidence suggests otherwise.
It is worth noting - that machine harvested fruit is not suitable for the production of all styles of wine. For example, some winemakers produce fine delicate Chardonnay & Rieslings by gently squeezing whole bunches using certain types of presses. Their aim is to minimise the degree of phenolic pickup in the juice as much as possible. Obviously this rules out machine harvesting as the majority of machine harvested fruit comes in as individual and partly juiced grapes. This also rules out Late Harvest or Botrytis grapes which are simply to fragile to be machine harvested.
So whether its machine harvesting or the good old traditional hand-picking, the on-going battle between man and machine has undoubtedly made its way into the wonderful world of wine.