Mothballing: Considerations When Taking Vineyards Out of Production

Cristopher C. Chen, Ph.D., Cooperative Extension, Division of Agriculture and Natural Resources, University of California, Hopland Research and Extension Center, CA

In 2024, the CDFA Grape Crush Report provided data that supports what winegrape growers are experiencing; tonnage of winegrapes crushed in California was down by approximately 21% from 2023 and approximately 20% when compared with the average of the previous five years [1]. In response, grape producers may look for options to reduce or eliminate vineyard management costs during this period of low demand. In 2024, self-reported, bearing acreage of winegrapes fell by 4% which is represented by a loss of 20,000 acres [2]. These values are self-reported by grape producers and are likely under representative of the actual loss of productive winegrapes across California. This reflects a removal of mature grapevines from either production status or complete removal of the vines themselves.

Recently, grape producers have been searching for alternatives to full vine removal that still allows them to adapt their operations to current market realities. Among those options is a concept called “Mothballing”; this term was first used by Australian grape growers in the early 2000s and refers to a form of long-term “storage” of grapevines without expectations of productivity. It can be more formally defined as: Maintaining a non-producing vineyard with minimal, critical inputs to allow for a rapid return to production in the future.

Mothballing vineyards provides another option for grape growers who may have barriers or no desire to remove their grapevines entirely. However, we have little peer-reviewed information to help identify the best practices for pursuing mothballing in a vineyard. Some work from Australia identifies reasons for mothballing and some basic strategies for success, such as integration of livestock [3]. Other work identifies various reasons for mothballing which include economic hardship, resource scarcity, and more[4]. However, the overall resources and available information are lacking as it relates to methods, time frame, and feasibility of mothballing vineyards anywhere in the world. In the current conditions winegrape producers face, it is essential to further explore the nuances of mothballing vineyards to ease the pressure of poor market conditions.

In Mendocino County, UC Cooperative Extension is beginning to explore the various approaches to mothballing vineyards. Through interaction with grape producers and review of literature, mothballing approaches could be easily categorized into three groups: (1) Type I Mothballing – No harvest planned with minimal management for pests only (2) Type II Mothballing – No harvest planned with management for pests and for later vine recovery (3) Type III Mothballing – Salvageable harvest with reduced management intensity. This categorization of mothballing practices is subject to change as new knowledge is developed in this field. Regardless of the grower’s approach to mothballing, management of pests and diseases will still be essential; this helps reduce pest pressure on neighboring vineyards and mitigate risk of the vineyard being declared “abandoned”. Each type can be summarized as follows:

• Type I: no vine management; little to no consideration to vine recovery after mothballing. Little to no inputs (e.g., water or nutrients)
• Type II: vine is managed for recovery after mothballing only; often pruning is the only practice preserved. Minimal inputs to preserve vine health and growth
• Type III: most practices are continued at reduced intensity, but extraneous practices are eliminated, and inputs are minimized

The majority of mothballing approaches have the primary objective of reducing labor hours to reduce per-acre management costs. Reduced vine management can lead to challenges with pest and disease control and may lead to increased pest pressure for neighboring farms and for the grower themselves as they try to return to production practices after the mothballing period has ended. This is a major concern when deciding to mothball a vineyard. However, some practices may be implemented at little cost to reduce pest risks. Targeting the reduction of canopy vigor can indirectly reduce pest and disease pressure in vineyards and can be achieved in a few ways at little cost.

Integration of livestock like sheep or goats has the potential to limit habitat and food sources for many pests and diseases. Livestock rotation in mothballed vineyards allows for both cover crop reduction and canopy management through feeding from the livestock. Reduction of foliar tissue and litter on the vineyard floor means less habitat for pests and fewer locations for pest overwintering. Livestock may be effective at reducing pest and disease pressure in vineyards where they are allowed to graze [5].

Livestock integration may not be an option in all grape growing regions and may be unavailable due to a lack of livestock sources or may be prohibitively expensive for the purposes of reducing vineyard management costs. To achieve a reduction in canopy vigor and reduce pest and disease pressure, another option could be the reduction or outright elimination of resource inputs into the vineyard. Reducing nutrient inputs can be relatively straightforward. Limiting macronutrient applications should help reduce vine growth over seasonal timeframes. However, growers should be careful not to let the vines fall too far into specific nutrient deficiencies to avoid long-term and lasting damage. Reduction in water inputs must be more carefully considered. Vines that have been cropped with ample irrigation over their lifespan may be significantly damaged from a total loss of irrigation water; likewise, vineyards on soil types that do not have substantial water holding capacity should not be completely cut off from irrigation water right away. Reductions in inputs has the potential to help reduce vine vigor in spring and summer and often leads to smaller canopies. Indirectly, this approach could also help lower pest pressure, especially if applied in conjunction with livestock integration.

There are risks when mothballing vineyards. Growers should be aware of the chance of long-term damage to grapevines. Losses of primary buds, reliance on latent buds for return to production, large pruning cuts when returning to production, and low inputs may all lead to vines with lower production potential upon the end of the mothballing period. There is little information related to the long-term impact of mothballing on vine health and productivity, on the success of various methods, or on the economic viability of mothballing on long time scales.

If you are planning to mothball your vineyard, it’s recommended that you discuss your plan with your neighbors prior to implementation. Having the information that a mothballed vineyard is nearby can help other grape producers respond to the potential for higher pest and disease risk ahead of any potential effects.

UC Cooperative Extension, North Coast Viticulture has started to pursue research into the efficacy and methodology of mothballing vineyards. This study plans to examine the effects of various mothballing practices on vine health, pest and disease pressure, and recovery of vines. Practices applied in this study will include livestock integration, low resource inputs, and methods to return to production. This work began in Spring of 2025 and will be seeking funding to expand and continue to pursue this topic going forward.

 

References

1. CDFA, Grape Crush Report 2024 Report, Final. 2024, California Department of Food and Agriculture.
2. CDFA, California Grape Acreage Report 2024 Crop. 2024, California Department of Food and Agriculture.
3. Kleeman, G., The Australian wine industry: from boom to gloom? Geography Bulletin, 2006. 38(4): p. 32-37.
4. White, R.E., Wither water in vineyards? Australian and New Zealand Grapegrower and Winemaker, 2009(551): p. 56-59.
5. Wilson, H. and K.M. Daane Review of Ecologically-Based Pest Management in California Vineyards. Insects, 2017. 8, DOI: 10.3390/insects8040108.