By Judit Monis, Ph.D.
Last August I participated in the 2nd International Table Grape Conference (CIUM 2025) in Lima organized by PROVID Peru ( the Peruvian association of table grape producers) as an invited speaker. I was asked to address the audience on plant health issues related to grapevine grafting. This is not surprising as I specialize in the study of graft transmissible diseases. Although I had performed virtual consulting work during the pandemic, this was my first time visiting the viticultural regions in Peru. Peruvian vineyards are mainly planted for the production of fresh grapes (table grapes) and pisco (a brandy produced from fermented grape juice). However, a small proportion of grapevine plantings are dedicated to wine production and these are found planted in higher altitude regions (sometimes higher than 10,000 feet) of the country. Most table grape varieties are patented by privately held genetic development companies. This presents a challenge to plant propagation as it relates to plant health. While patented varieties are highly traced and inspected for consumption quality features, they do not participate in certified programs and often, it is difficult to obtain information about their health status. Therefore, it is common and expected to find these varieties infected with graft-transmissible pathogens due to the nature of propagation and the trend of grafting onto rootstocks (material could be infected with graft transmitted pathogens prior to grafting).
Grapevine Diseases Present in Peruvian Vineyards
We know that grapevine pathogens (disease causing agents) originated in the same place where Vitis (the grapevine genus) species originated. These disease agents (bacteria, fungi, and viruses) were introduced to other places in the world with the grapevine propagation and planting material. Specifically, the varieties and clones that are grown in vineyards around the world belong to the Vitis vinifera species (of Eastern European and Asian origin) while the rootstocks grown commercially belong to American Vitis species. When grape cultivation started countries were not set up with quarantine programs, neither modern diagnostic tools we use today (e.g., deep sequencing, PCR, ELISA, etc.) to detect pathogens were available. Consequently, since the early days of grapevine cultivation European and American grapevine pathogens have been moving from one site to another for many generations. Further, with the present trend of grafting grapevine varieties to rootstocks that are resistant to phylloxera, salinity, and nematodes there is an increased potential of disease transmission There has been a limited amount of testing surveys in Peru, however, the commonly known diseases caused by fanleaf virus Leafroll viruses, Pinot Gris virus, Vitiviruses, and fungal trunk pathogens have been reported to be present in Peruvian vineyards. My own work has shown the presence of the Red Globe strain of Grapevine leafroll associated -2 (GLRaV-2 RG) and fungal pathogens. The most frequently found fungi associated with trunk diseases found were: Phaeomoniela, Phaeoacremonium spp. and Ilionecrtria (previously known as Cylindrocarpon spp.) species. These pathogens cause rapid and severe decline of plants. In the projects I was involved, up to a 70% mortality was observed three years after planting. Although, it is difficult to be a detective when we perform testing after a vineyard has been established, my suspect is that the virus and fungal pathogens were imported to the vineyard with nursery planting material. Therefore, it is critical that foundation and nursery plant material be tested for important pathogens prior to their propagation and planting.
The Climate in Northern Peru Allows Two Yearly Harvests
During my time in Peru, I had a chance to visit productive vineyard blocks in the Ica region. My visit in August coincided with the South American winter season. I was surprised to see that the vineyard blocks had green foliage and were flowering, rather than being dormant as expected in other grape growing areas I have visited! I learned that due to Peruvian mild climate, it is possible to manage artificially the vineyard blocks to induce them to produce fruit in desirable timeframes. To accomplish this, the application of chemicals is needed to induce dormancy. Manipulating the harvest time is a trade advantage as the fruit can enter the American, Chinese, and/or EU markets without competing with Chilean produced fruit. In the Northern Peruvian grape growing areas such as Piura with a warmer and desertic climate, certain vineyard blocks are managed to allow two yearly harvests. This strategy is used to increase producer’s profits, recuperate investments earlier, and have more flexibility entering the export market. Highly fertile and vigorous grape varieties that are pruned twice a year to allow an additional harvest are planted in Piura. The double harvest practice is only possible when applying climate protection systems, such as removable or fixed plastic covers to protect the crop from inclement weather. Although this trip did not allow a personal visit to the Northern region, it was impressive to see the extensivity of the high-tech infrastructure utilized for grape growing from my airplane window. In my opinion, while the increased production of grapes in Peru may appear to be profitable, the vineyard operation creates added stress to the vines. Consequently, if applied long-term the life span of vineyards will be negatively impacted as stressed vines are more susceptible to diseases caused by bacterial, fungal and/or viral pathogens.
Conclusions
Plant certification programs have been developed worldwide to reduce the risk of introducing and propagating plant pests and/or pathogens that are detrimental to grape production. Although, certification programs are not perfect and do not exclude every important pathogen, it provides one extra level of confidence. My Peruvian colleagues have voiced concern and wish SENASA (the equivalent to USDA APHIS – plant health inspection service) would provide formal quarantine and testing of introduced patented varieties into the country. Plants of patented varieties are restricted, and although they are propagated locally, they had been imported from areas where pathogens are present. It is my hope that in the future, genetic companies that produce patented grapevine varieties be more transparent and participate in quarantine and certification programs to avoid carrying important pathogens that could cause important outbreaks.
Judit Monis, Ph.D. provides specialized services to help growers, vineyard managers, and nursery personnel avoid the propagation and transmission of disease caused by bacteria, fungi, and viruses in the vineyard.
Judit (based in California) is fluent in Spanish and is available to consult in all wine grape growing regions of the word. Please visit juditmonis.com for information or contact juditmonis@yahoo.com to request a consulting session at your vineyard.
