A Closer Look At Grape Splitting
A number of factors can contribute to grape splitting, and this summer, Eric Stafne, Mississippi State University associate extension/research professor – fruit crops, began exploring some of these possible causes in greater detail.
Stafne and his colleagues looked at nine cultivars grown in Mississippi: Blanc du bois, Champanel, Cimarron, Conquistador, FAMU99, MidSouth, Miss blanc, Victoria Red, and Villard blanc. These varieties were chosen in part because they had not previously been tested for splitting tendency.
Part of the study included considering spotted wing drosophila’s role in grape splitting. “We wanted to see if there was any correlation between splitting and infestation with SWD,” Stafne says. “Preliminary results show that SWD doesn’t really like these types of grapes apparently, but we don’t have the final results, so I can’t say one way or another whether there’s any relationship or not.”
Stafne says one of the most interesting findings was that the majority of the varieties did not split, and skin thickness didn’t seem to play a part in splitting tendency. For example, Victoria Red, a relatively new table grape released out of Texas, has fairly thin skin but did not split.
“That was a surprise to me,” Stafne says. “Some of the others – even though they had a thicker skin – did split some, including MidSouth and Conquistador.”
The researchers also looked at how sugar levels and firmness affect splitting but found no correlation. “It seems to be genotype by environment interaction, as far as we can tell,” Stafne says.
Physiologically speaking, grape splitting occurs when water movement across the skin into the berry causes cells in the berry to expand, Stafne explains. Heavy rainfall can cause more splitting, as can improper irrigation. “If you have a really dry period and then you dump a lot of water through irrigation, that can lead to splitting,” he says.
To reduce the risk of splitting, Stafne recommends being consistent with irrigation and not letting the vines get too dry. “If you have a dry period, and you’re not irrigating, don’t go whole-hog and dump a lot of water on there,” he says. “Gradually ease the vines back into it.”
Stafne notes that there’s more work to be done in terms of fully understanding splitting. “I don’t know exactly the mechanism of why they’re splitting and not splitting yet, but it’s something that we’ll continue to look at,” he says.
More information on the study can be found on the Mississippi Fruit and Nut Blog.