Grapevine pruning is an essential vineyard management practice that helps maintain plant health and fruit quality. However, this practice also exposes vines to various fungal diseases that can be detrimental to vineyard health. In this blog, we share how to understand pruning wounds and discuss the protection options.
How Infection Enters a Vine
When a grapevine is pruned, and a wound is created, it becomes susceptible to infection from various pathogens known as grapevine trunk diseases. These diseases are caused by a group of fungal species called Ascomycota fungi. These fungi can produce fruiting bodies that release spores during the winter, and the spores can land on pruning wounds and cause infections.
Pruning wounds act as entry points for these pathogens, similar to how an unprotected cut in the skin can be a pathway for microorganisms to enter the body. Grapevine trunk diseases encompass a wide range of pathogens, with over 140 fungi associated.
How Spores Find Their Way into Pruning Wounds
The ascomycin pathogens produce two types of fruiting bodies – pycnidia and perithecia. Pycnidia are flask-shaped structures filled with spores, and when precipitation occurs in the vineyard, these pycnidia can be activated and release their spores onto the surface. Rain splash or strong winds can then carry these spores to adjacent vineyard areas, resulting in passive movement.
The pathogens also produce perithecia, which have external sacs containing spores. These fruiting bodies forcefully shoot their spores into the air, which can then be picked up by wind and spread over long distances.
How the Infection Occurs Once the Spore is On the Cut Surface
Once the spores land on the cut surface of the pruning wound, they can germinate quickly due to the sap accumulation that occurs. Similar to a seed sprouting, the pathogens from the spores begin to germinate. Once they have germinated, they can penetrate the wound and start colonizing the area. This initial colonization allows them to multiply and spread from the pruning wound to other parts of the plant.
The Biologicals Process
Biologicals introduce beneficial organisms, such as trichoderma-based fungi or bacterial species, onto the pruning wound. These organisms are non-pathogenic and can colonize the wound, using the sap and nutrients to grow and establish themselves. Unlike synthetic chemicals that only provide temporary protection and need to be reapplied, biologicals aim for long-term sustainability.
These organisms act as a barrier on the pruning wound surface, similar to a protective shield, and can remain effective for extended periods. The specific mode of action varies depending on the biological used. Still, the goal is to have the organism outcompete and prevent the colonization of harmful pathogens, ultimately protecting the pruning wound.
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