Trunk disease management in California

Preventative practices in young vineyards, Post-infection practices in mature vineyards

 

Figure 1

Figure 1

These management guidelines were developed by plant pathologists Kendra Baumgartner, Renaud Travadon, and Mizuho Nita, viticulture farm advisor Monica Cooper, and economist Jonathan Kaplan (Figure 1).  Our collaborative efforts to develop these guidelines are funded by a grant from the USDA-NIFA Specialty Crops Research Initiative (SCRI).  The need for these guidelines (specifically, for guidelines that emphasize the importance of timing practices according to disease incidence and demonstrate the economic benefits of preventative practices) arose from several studies on the usage and perceptions of trunk disease-management practices by grape growers and pest control advisers (PCAs, http://dx.doi.org/10.1094/PHYTO-10-15-0250-R).  The guidelines draw from the experience of and technical reviews by the UCCE viticulture farm advisors, published studies by UCCE Extension Specialists Doug Gubler and Philippe Rolshausen, and the collective work of trunk disease research from the US and abroad.

These guidelines apply to management of the four main trunk diseases: Botryosphaeria dieback, Eutypa dieback, Esca (aka Measles), and Phomopsis dieback.  For details on the diagnosis and spread of trunk diseases, see a presentation by Kendra Baumgartner at http://www.vineyardteam.org/virtual-tailgates/pruning-diseases/ or visit the disease diagnosis page on our SCRI project website at http://treeandvinetrunkdiseases.org/trunk-disease-pamplet/do-you-have-a-trunk-disease

Figure 2

Figure 2

Typically, under conditions favorable for disease establishment and spread (susceptible cultivar, high pathogen pressure, lack of disease management), disease incidence increases as a vineyard matures.  For example, in a susceptible cultivar such as Colombard, by year 10, approximately 20% of the vines are symptomatic (Figure 2).  Although they are caused by different pathogens, trunk diseases cause, the following general canopy symptoms appear: dead spurs, dead cordons, stunted shoots, and/or symptomatic leaves. By year 15, up to 75% of the vines may have canopy symptoms.  This sharp increase in disease incidence is not due to a higher level of susceptibility in years 10 to 15, but rather that visible identification of canopy symptoms occurs years after wood infections are already well established.  To lessen this sharp increase, preventative practices should be adopted when the vineyard is young and healthy in order to minimize infection of pruning wounds.  Once disease incidence is high, however, management based on prevention is no longer optimum, and you should instead focus on post-infection management practices.

To describe the most relevant practices for the different levels of disease incidence encountered in the vineyard, we outline three scenarios here.  The first is Scenario 1, which applies to a young vineyard, 3 to 5-years-old (Figure 3).

Figure 3

Figure 3

The vines are trained and undergo annual pruning.  Symptoms are absent or at very low levels.  Disease incidence can vary according to factors such as cultivar susceptibility and which trunk pathogens are present in the vineyard; symptoms can appear sooner with very susceptible cultivars and when vines are infected by very aggressive pathogens.  Therefore, we provide a range of vineyard ages for scenario 1.  However, we emphasize that disease incidence, and not vineyard age, should be the key criterion in developing a management plan.

 

We expect preventative practices to be most effective for scenario 1 (young vineyard, 3 to 5 years old with few to no symptomatic vines) because they minimize infections of pruning wounds, thus maintaining disease incidence at low levels. Preventative practices that may be implemented include (Figure 4)

Figure 4

Figure 4

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