In some years, spring frost damage can be catastrophic to vineyards. In some cases, huge crop losses can occur before the growing season as even fully begun. Researchers have developed a novel new way to fend off early spring frost damage in vineyards, based on a naturally occurring, frost preventing, phenomenon from a unlikely source: bacteria.
Common frost prevention techniques in vineyards include using sprinklers, fans, or heating methods to prevent damage to delicate spring vegetation. These techniques can be effective, depending on the specific circumstances of the vineyard, but also can be expensive. University of California Cooperative Extension advisor Glenn McGourty, and Professor Steve Lindow, a plant pathologist from UC Berkeley, have developed a new approach for vineyards, based on years of research in other crops, and examining how ice forms on leaf surfaces.
Microbiology’s role in Vineyard Frost Damage
These researchers have determined that ice formation on vines, as well as on cover crops and on soils usually occurs in the presence of Pseudomonas syringae, a bacteria that is also find in high altitudes and collects moisture from the air to nucleate ice particles in a process known as bio-precipitation.
McGourty and Lindow discovered that, by using copper as a bactericide, they were able to greatly reduce the population of Pseudomonas syringae on grapevines, and as a result the vines could withstand temperatures of 3 degrees (F) below freezing before ice formation, and frost damage, occurred. These additional 3 degrees can make a huge difference in preventing potential frost damage. McGourty reports that over the last 10 years, in the Ukiah Valley of Mendocino County, where he works, 90 percent of frost damage cases occurred in vineyards where temperatures did not drop below 29.5 degrees (F). Because winegrapes are grown in regions where spring frost is not usually severe, most wine growing regions worldwide, could likely expect similar results.
Manipulating the Vineyard Microbiome
While copper has been primarily used in the researchers’ trials to reduce Pseudomonas syringae populations, they are now looking ways to affect the leaf surface’s microbiome with beneficial bacteria, avoiding toxicity concerns associated with copper applications. McGourty and Lindow have focused on Pseudomonas fluorescens A506 as a beneficial bacteria because it is common and safe to humans and animals, and it can out-compete Pseudomonas syringae on leaf surfaces. Most importantly though for frost damage prevention, it does not nucleate ice formation. This bacteria has been show to naturally prevent frost damage in pears and citrus at below freezing levels. McGourty and Lindow have been developing a way to dilute pure cultures of Pseudomonas fluorescens A506 in water and apply to leaf surfaces using a standard spray rig. These applications of the beneficial bacteria are now being tested in vineyards as an alternative to copper, sprinklers, fans or heating, for frost damage prevention and its potential is very exciting for grape growers.