Trunk Diseases Within New Zealand – a Literature Review

Introduction

New Zealand harbors many trunk diseases which risk the New Zealand Viticulture and wine industry. Therefore analysis of these trunk diseases and there effects on grapevine cultivars is vital to the New Zealand wine industry. This review aims to tackle each of the trunk diseases in New Zealand in alphabetical order. Then the review will address how these diseases can be controlled. The main aim of this literature review is to understand New Zealand trunk diseases; then discuss the management practices that can be put in place to control these trunk diseases and their spread.

The trunk diseases that are currently in New Zealand are Botryopheria dieback, Eutypa dieback, and petri disease and part of the esca complex. These diseases have been found to contribute to low sugars and nutrients in the fruit of the berry. These diseases can also cause vine death and young vine death. The trunk diseases also effect the translocation of nutrients throughout the plant, this in turn affects the plant as it can no longer supply nutrients easily to other points of the plant. Each disease listed in this document have different symptoms specific to the disease. Botryospheria and Eutypa dieback diseases however have very similar symptoms, therefore it can be very difficult to identify the difference between the two when a trained person is monitoring a vineyard.

New Zealand trunk diseases are the same organisms that exist overseas and they are the same organisms that have been the cause of economic loss overseas. One of the cases where this has occurred is California who as of 2014 annually lose 260 million a year from Botryospheria dieback and Eutypa dieback diseases. Trunk diseases have caused other damage to overseas wine industries for example in France dealing with trunk disease has cost a total of 1.14 billion euros. This demonstrates the significant economic losses at stake from trunk diseases if left unmanaged. New Zealand may face similar losses in the future if a greater understanding of trunk disease is not found, therefore this document is meant to be used as a tool to allow greater understanding of vineyard trunk diseases and the management practices used to control these diseases.

All diseases within this document have treatment options these will be addressed collectively at the end of the discussion of New Zealand trunk diseases. This is mainly because two out of the three diseases that pose a significant risk in New Zealand can be managed and controlled in a similar way. The Exception to this rule is young esca/ young vine decline which has different management procedures to that of Botryosperia dieback and Eutypa dieback. Young esca has control mechanisms that require the nursery to take responsibility to ensure clean grafts and good vineyard hygiene, to help with the spread of the disease and to attempt to prevent it from infected newly planted vines and vineyards.

Botryosphaeria dieback

botryosphaeria dieback Is a disease that can affect the trunk of the grapevine. Botryosphaeria dieback can enter though open wounds in the grapevine. This disease is commonly spreads via the wind and rain splash, making it a disease which spreads easily throughout the vineyard. Botryosphaeria has the ability to overwinter in grapevines and remain in the vine till spring returns. This means after winter the disease will re surface the next phenological year.

Botryosphaeria dieback has been known to delay bud break, and cause weak shoots on the grapevine. An infected plant may also have cupped leaves when symptomatic. Botryosphaeria may also appear as a lack of shoots in during the development of the canopy. In a worst case scenario a vine may fail to break dormancy in spring and summer because it is diseased with botryosphaeria dieback. Botryosphaeria dieback can cause dead necrotic in the xylem of a grapevine, causing canker sores and death of parts of the trunk. This process will eventually lead to vine death and a place for fruiting bodies of Botryosphaeria dieback to inhabit.

The blockage of the xylem tissue within the grapevine prevents translocation of nutrients in the grapevine, this will affect the vines leaves and fruit, effecting natural soluble degrees Brixs and yeast assimilable nitrogen content in the berry. For example soluble degrees Brix of non-diseased fruit was 22.3, where as in diseased fruit this was only 21.4 Degrees brix. Most Botryosphaeria symptoms appear only after 8 years of propagation however such symptoms are still possible before this time. The optimum temperature for infection of Botryosphaeria dieback is between 23 and 26 degrees Celsius.

Esca Complex

The Esca complex is a series of different organisms that make up Esca and Petri disease. The Disease Esca does not exist within New Zealand currently. It must be noted however that there are parts of the complex that have been observed within New Zealand. Although some of the parts of the complex within New Zealand may not be a risk right now they may pose a risk in the future. This is why it is included in this list as it is something that cannot be ignored in the long term.

Esca is a set of diseases that colonizes the xylem tissue inside the grapevine, blocking the Xylem tissue and the transportation of nutrients around the plant. Therefore the disease causes wilting of the leaves. The Disease also causes the leaves to get brown or purple spots. Esca can survive over winter as it can survive in cracks in the trunk. Esca is a disease that has two types of disease spread these are Asexual and Sexual stages of the disease.

The Esca disease causes dark spots on berries that often appear between fruit set and ripening phenological stages of the grapevine. The disease Shrivels berries and can cause them to dry out on the grapevine. Shoot tip dieback can occur on grapevines early in the season with this disease, this causes defoliation on the shoots and eventually shoot dieback. When leaves are produced interveinal Leaf chlorosis will persist throughout the canopy. Esca will eventually cause vine death if left untreated.

Eutypa Dieback

Eutypa dieback is a trunk disease that effects vines in a similar way to Botryospheria die back as it blocks the Xylem and causes a wedge of dead Black tissue to form inside the trunk. The disease grows and spreads Readily in high rainfall Especially in areas where rainfall surpasses 600mm per year. Eutypa dieback spreads though open wounds on the grapevine the disease usually appears after the first 10 years of growth.

This disease will make the vine decline in health slowly over time. Eutypa dieback and Botryosphaeria dieback are made from a mixture of different organisms such as libertella blepharis for Eutypa dieback, and Botryosphaeria Stevensii for Botryosphaeria dieback.

Eutypa dieback can cause vine cankers along with death of the vine. Any dead wood on the vine becomes an area where fruiting bodies can be produced and spread from. The disease spreads through rainsplash and water pooling. Where cuts have been made to the vine, in an area prone to water pooling or water accumulation proper care must be taken to prevent Eutypa infection.

Petri disease

Petri disease is a trunk disease which is present in New Zealand. Called Young vine decline it often leads to the stunting of growth and the death of young vines. Within the first 5-6 years of growth the disease can cause early defoliation, along with leaf chlorosis. The disease is part if the Esca complex and is usually derived from infected rootstock. This disease can cause black staining of tissue within the grapevine.

Petri disease usually comes from infected rootstock before grafting, the disease can restrict root growth along with shoot growth the vine is usually affected significantly. Petri disease is part of the Esca complex, however it does not represent the Esca disease. Petri disease can slow root growth and Black vascular streaking as the tissue inside the plant is affected by the disease. This disease usually enters into the grapevine while the plant is at the nursery or being established into a vineyard through the damage in the rootstock causing infection. This disease kills the trunk of the vine.

Control measures

Botryospheria and Eutypa dieback

Preventing damage to the grapevine is a core part of Botryosphaeria and Eutypa dieback management. Both of these diseases infect grapevines though wound sites, these wounds could be caused by anything including under vine mowing and pruning. A good way to prevent Botryospheria and Eutypa dieback is through a process of Covering wounds with a pruning paste. To prevent disease from getting into the grapevine.

If a vine is partially infected Cutting off the infected wood will stop the spread of the disease given that Pruning dressing is applied to any wounds related to this process on the grapevine should stop the spread of these diseases. If the vine is fully infected it needs removal as it cannot be recovered.

Petri disease control

Petri disease can be managed though proper practices taken in the Nursery while grafting grapevines. Ensuring that all propagating material such as rootstocks are clean and healthy is a step in the right direction. These practices can be paired with waxing and dipping the newly grafted grapevines in fungicide, along with removing all deadwood and sterilization of pruning equipment and grafting equipment.

A lot of the processes involved in the Grafted Grapevine Standard cover the control of vine diseases when grafting, in the vine health area of the standard. Therefore to qualify to sell grafted grapevines in New Zealand you must give an assurance that proper sterilization and hygiene was carried out on the budwood and rootstock before vines can be sold. Due to this standard New Zealand has a lower likelihood of having this disease in newly grafted grapevines.

Esca disease control

The Control of esca runs upon the same lines as other trunk disease controls. The best way to deal with esca is to use Pruning pastes, and not to make large cuts during the rain or when rain is expected. Esca disease spreads easily in the rain therefore large cuts should not be made during heavy rainfall. Double pruning and late pruning has been found to have a slight effect on the progression of esca trunk disease. Fortunately this disease is not within New Zealand in the form of esca, however it is important to understand the control mechanisms to prevent esca as it has the ability to develop in New Zealand should the conditions be correct to do so.

The current esca diseases within New Zealand include the white rot stereum hirsutum, along with many other species of wood staining fungi in the esca complex. These include fungi in phaeacremonium species. Esca has no chemical ways of controlling the disease that are currently available, therefore this is why prevention practices need to be carried out in place of other forms of control.

Conclusion

Vineyard practices determine the overall control of New Zealand trunk diseases, without proper vineyard management the industry would be at risk from a lot of these diseases. This is because solving them requires good vineyard hygiene practices and following protocol correctly when it comes to grafting grapevines, and general vineyard procedures. If good hygiene is not maintained the vineyard will get infected with trunk diseases, this will effect fruit and berry composition in the short term and will kill and effect grapevine growth in the long term.

Trunk diseases are significant for the wine industry as they can damage vines and greatly effect crop and yield. The diseases can be very difficult to manage once infected, therefore it is very important for a viticulturalist/vineyard manager or owner to understand the signs of trunk disease on a vineyard. This is so the area can be tended to immediately, and further action can be taken to stop the spread of the disease quickly and effectively.

Trunk diseases in New Zealand often affect the xylem tissue of a plant preventing translocation of nutrients within the grapevine. This is important when considering trunk diseases as it demonstrates the risk of plant death and the costly prospect of block or vineyard re-establishment. To prevent such re-establishment issues it is sensible to consider these diseases as a risk in the pest and disease short term and long term management plan for the vineyard.

Trunk disease can affect the translocation of plant nutrients and therefore effect the nutrients inside the bunches on the grapevine. A lower soluble brix and lower Yan can lead to stuck ferments and lower alcohol concentrations. From a viticulture standpoint it can lower brix levels therefore lowering the price of the fruit from the effected vines or the effected vineyard. This means it will be more costly to fix the problem the longer the infection is left in the vineyard.

Trunk disease uses dead wood to spread spores throughout the area, therefore with any trunk disease it is best to dispose of dead wood and dead vines as fast as possible to avoid the spread of disease throughout the vineyard. Disposing sources of inoculum will make a big difference to the rate of infection on grapevine cultivars as it will mean less spores exist in the vineyard that can inoculate disease on vines. Trunk diseases have the ability to inoculate from any freshly cut wound sites, therefore this is why it is important not to prune in the rain or do mowing before a large expected rain event as these impacts may damage the vine and therefore open up an infection point for disease.

The symptoms of Botryospheria dieback and Eutypa dieback are very similar therefore it can be very difficult to tell the diseases apart without further testing although this does not pose a significant problem for growing grapevines. It is important to understand the differences between the two diseases for accurate representation of a particular disease and the effects that disease on a vineyard. For example Botrytispheria dieback may cause a lack of shoots or no shoots on a particular area of the vine in spring, knowing this allows the vineyard manager to plan the next moves for the vineyard and the crop and sugar content of the grape before fermentation.