Fact Sheet VITICULTURE Grapevine recovery after fire Fire damage to grapevines Fire may damage grapevines to different degrees depending on the intensity and time of exposure to fire or radiant heat. It is important to understand the impacts of the damage on the long-term viability of vines in order to make decisions about how they should b e managed after fir e exposure . The major cause of long-term vine decline or death after fire exposure is damage to the vascular system, the structures which transport water and nutrients between the roots and leaves, in the permanent structures including the cordon, trunk and roots. Understanding the extent to which these structures are damaged can help growers adopt the best management strategies to maximise long-term recovery of the vines. Vascular tissue that is white or green is healthy; tissue that is yellow or light brown is damaged and deteriorating; and tissue that is darker brown is dead (Figure 1). Different levels of damage may occur irregularly around the trunk depending on the duration and location of the fire exposure. Damage to the vascular tissues is permanent and depending on the degree of damage may reduce long-term grapevine viability. Updated January 2020 Fact Sheet VITICULTURE Figure 1. A fire-damaged grapevine trunk showing browning of the vascular tissue (left) and healthy grapevine vascular tissue (right). Assessing vine damage and promoting recovery Damaged tissue of vine shoots, leaves and inflorescences/bunches grown in the current season will not recover. Vines with a small proportion of damaged shoots, leaves and bunches may continue to grow and produce a successful crop; however, vines with a high pro portion of d amage w ill not. In cases where the damage is moderate, the removal of remaining bunches should be considered to promote the recovery of the vines during the remainder of the season. Because there are no non-destructive measures to assess the damage to the vascular system, visual assessment of vine damage may provide a useful guide to the potential for long-term recovery. Irrigation If there is a chance that the vines can be saved or if damage is variable and there are vines which are unaffected by fire, the first priority is to re-instate irrigation to the vines, especially if ongoing dry conditions are forecast. If irrigation infrastructure such as driplines has been damaged, getting it working is paramount. Temporary irrigation systems such as movable sprinklers or furrow irrigation may be useful as an interim solution to ensure vines receive water. Visual assessment of fire-damaged vines Assessing individual blocks and mapping the damage to vines, irrigation, trellis and fencing helps to visualise the damage, to quantify losses and to identify priority areas for attention and redevelopment. It is useful to categorise the severity of vine damage into groups based on visual assessment of the vines and to relate this to the management approach to be taken (Table 1). It is Updated January 2020 Fact Sheet VITICULTURE important to remember that vines will continue to decline during the weeks after the fire and early assessment may not reflect the final status or survival of the vines. Table 1. Example categories for visual assessment of fire damaged vines and potential remedial actions Category Description Action Severe Leaves, shoots and Consider trunk and trunks are damaged. The cordon vascular system is likely redevelopment. to be severely damaged. Moderate Vines have a high Consider trunk and proportion of damaged cordon leaves. Trunk damage redevelopment. may be visible. High potential for damage to the vascular system. Vines may recover with reduced capacity. Minor Vines have a low Continue usual proportion of damaged irrigation and pest leaves and are otherwise and disease unaffected. Vines are control. Consider expected to recov er next bu nch re moval to season. promote vine recovery. Undamaged Vines have not been Continue us ual exposed directly to irrigation and pest flames or radiant heat and disease from fires and show no control. signs of injury. Updated January 2020 Fact Sheet VITICULTURE Vine recovery and vineyard redevelopment after fire Buds and shoots may start to appear within weeks after fire damage. In some cases, especially after hot and dry conditions, new shoots may collapse and dry out. This is caused by damage to the vascular system preventing the flow of water within the xylem to the shoots and leaves. Significant damage to the phloem will have a girdling effect, whereby carbohydrates generated by the leaves are prevented from reaching and replenishing the root system. These vines may start to decline and die over the coming weeks, months and years. Recovery of vines after fire is variable and it can take several months for the full extent of the damage to become apparent. In some cases, where the damage to vines is severe, if the block has a history of poor performance or if a new variety, clone or rootstock is desired, the best action may be to completely remove the vines and replant the block. In an own-rooted vineyard, if the vines are to be retained, it is recommended to confirm that they are viable by waiting for new growth to appear below the fire-damaged tissue. Vines with healthy tissue at the base of the trunk or below the ground may start to produce new shoots from the base within a few weeks after the fire (Figure 2). This new growth should be allowed to grow and lignify. In winter, the damaged trunk and cordon can be removed and a strong shoot from the base retained to form a new trunk. If there is sufficient time left in the growing season to develop a new trunk (at least 12 weeks), it may be desirable to immediately remove the damaged trunk and cordon. Before deciding which action to take, growers should consider the length of time left in the season for regrowth and retraining to occur and the availability of funds and labour to adequately complete the job. The advantages and disadvantages of taking immediate action compared to waiting for signs of recovery are listed in Table 2. Figure 2. A new shoot growing from the base of a fire-damaged vine trunk, four weeks after the fire. Updated January 2020 Fact Sheet VITICULTURE Table 2. Advantages and disadvantages of immediate action after fire damage compared to waiting for signs of vine recovery Action Advantages Disadvantages Wait for signs of No immediate expenditure required Re-growth may occur at varied vine recovery Improved accuracy of damage heights assessment Damaged trunks may be Avoiding expenditure on vines that do susceptible to trunk diseases not survive Immediate removal Trunk removal may be quicker without Wasted expenditure if vines do of damaged trunks new growth at the base not regrow If sufficient time remains in the growing season, trunks may be re- established in the same season Vines growing on rootstocks pose a challenge for reworking after fire damage. If the rootstock regrows, this may be left to redevelop a new trunk and a scion can be grafted on to this in the following year. Alternatively, if there is sufficient rootstock remaining after the damaged tissue is removed, a new scion can be grafted close to the ground level. Other things to consider after fire damage to vineyards Stay safe Smoke and ash can be toxic. It is important to follow the advice of government agencies before re- entering an area damaged by fire and wear appropriate protective equipment, especially when dealing with burnt CCA-treated posts. Written records Accurate record-keeping is recommended for insurance and other pu rposes. Maintain a detailed record of any damage incurred, significant dates and the remedial actions taken. Records may include photographs and the time taken on recovery activities. Rubbish removal Fire-damaged vineyard posts, wire and driplines should be separated and stockpiled. The local Environmental Protection Agency can provide advice on disposal. Risks of erosion Burnt vineyards may be at a greater risk of soil erosion. Temporary control of water run-off may be achieved using contours or hay bales. Updated January 2020 Fact Sheet VITICULTURE Acknowledgement This work was supported by Australia's grapegrowers and winemakers through their investment body Wine Australia, with matching funds from the Australian Government. The AWRI is a member of the Wine Innovation Cluster in Adelaide, SA. Further reading Collins, C., Gao, H., Wilkinson, K.L. 2014. An observational study into the recovery of grapevines (L.) following a bushfire. Am. J. Enol. Vitic. 65 (3): 285-292. Whiting, J. Recovery of grapevines from fire damage. 2012. Aust. N.Z. Grapegrower Winemaker (580): 25-31. Whiting, J. Options for managing fire damaged grapevines. http://agriculture.vic.gov.au/agriculture/horticulture/wine-and-grapes/options-for-managing-fire- damaged-grapevines Hincksman, M. Preparing your vineyard for fire. http://agriculture.vic.gov.au/agriculture/horticulture/wine-and-grapes/preparing-your-vineyard-for- fire Scarlett, N. Needs, S. Downey, M.O. 2011. Assessing vineyard viability after bushfire. Aust. N.Z. Grapegrower Winemaker (564): 21-25. Whiting, J. Grapevine recovery from fire damage. https://www.awri.com.au/wp- content/uploads/grapevine_recovery.pdf Wilkinson, K. Collins, C. 2010. Grapevine recovery following fire damage. Aust. N.Z. Grapegrower Winemaker (556): 42–43. Rose, B. Pruning smoke, fire and heat-impacted vines. 2009. Aust. N.Z. Grapegrower Winemaker (545): 34–35. Contact For further information, please contact: AWRI helpdesk Phone 08 8313 6600 Fax 08 8313 6601 Email [email protected] Website https://www.awri.com.au/industry_support/winemaking_resources/smoke-taint/ Address Wine Innovation Central Building, Corner of Hartley Grove & Paratoo Rd, Urrbrae (Adelaide), SA 5064 Updated January 2020