From the late 1990’s sporadic articles and research documents have sprung up here and there about the Grapevine Leafroll threat in South African vineyards. Since then, numerous more appeared, most asking the question: “What is actually being done about this?”.
I wrote an article about this a while back called “Grapevine Leafroll Virus – A National Viticultural Crisis”, which highlights the dilemma we are currently in.
So what are the industry leaders (except for some individual farms like Creation, Vergelegen and now Delaire Graff) really doing about this pandemic, besides a lot of research with no real measurable action plan to win this battle? Looking at the state most vineyards are in – especially in Stellenbosch, the sad truth is “not a lot”.
I consult on a couple of farms that have vineyards infected anything from 30-80% with GLV. The difference is that we have a 10 year plan to eradicate this virus on these specific farms – a plan that few farms have, especially with regards to Cabernet Sauvignon, due to the high demand for this noble grape.
Companies like Rupert & Rothschild and DGB are adamant on buying grapes from blocks that has no virus, an ever increasing difficulty facing them as production teams.
I was frustrated that I couldn’t do more to get an initiative going to help and promote better practices amongst estates and producers. But that all changed on the 3rd of May 2017, following a stunning vertical tasting at Delaire Graff wine estate, presented by winemaker Morne.
The concept of ultra-premium luxury goods are nothing new to the Graff family, so it was only natural that they have the same philosophy towards the wines they produce. But something was threatening this quality concept on their farm – Grapevine Leafroll Virus. They uprooted about 60% of the vineyards in 2009, replacing them with virus free material. The strategy onwards is to replace whatever vine shows signs of GLV with new vines the next year. The remaining vineyards had about 350 vines replaced in the first year. That same vineyard saw a replacement of a mere 10 vines in 2016, making this vineyard almost 100% GLV free.
So that made me think. I know not all producers are in the financial position to replace 60% of their vineyards, but if we can start a nationwide program where the producers start replacing infected vines yearly – all according to what they can afford – we can actually start to track our progress in fighting this pandemic head on. With less and less infected vines to feed on, coupled with following proper mealybug and ant control protocols, we can surely defeat this virus in our vineyards.
So was born the Grapevine Leafroll Eradication Program™
This program is 100% voluntary, non-regulated and purely based on honesty. All you need to do is sign up and submit the amount of vines per variety that you replaced in that year. Submissions are done by the end of September each year. Each year after submission you will receive a digital participation certificate.
This list will also serve as a trading platform, giving companies and winemakers insights as to who is actually serious about this and who they can create a long term relationship with, virus free and quality guaranteed.
Grapevine Leafroll Control Strategy – The Process
- Counting infected vines
- This must be done annually to determine the percentage vines infected. This will determine whether you follow a control strategy or replacement. Use a GPS to mark the vines for future reference and to keep track of vines infected and replaced. This will ultimately show where problem areas exist
- More than 20% infection I would suggest only to control ants and mealy bugs
- Less than 20% infection I would follow a replacement strategy
- Control Strategy
- During the growing season
- The aim is to control the spread of the virus through vectors. The main goal is to control ants and mealy bugs (they spread the virus). This is done by means of an integrated pest management program making use of chemicals and natural predators
- Ants must be controlled immediately when activity is visible. Take a look at the IPW site so see registered products.
- The mealy bugs must be controlled by releasing natural predators – a combination of Wasps and Ladybugs – rather than with pesticides
- After harvest
- The use of Imidacloprid plays an integral role in the control of mealy bugs that feed and survive on the roots of the vineyards. Administer every 3 years (Every 2 years where mealy bug pressure is high)
- Keep in mind that Imidacloprid has a with holding period of more than 3 months when administered at budding
*It is important to keep in mind, when you have newly established vineyard next to an infected block, to apply a total control strategy around a buffer zone of about 25 meters in and around the infected vine to prevent the spread to the new block.
- Replacement Program
- Imidacloprid must be administered in the year that plant removal is planned. This is done after harvest and aims to kill mealy bugs that feed on the root system
- Infected vines must be marked early autumn – red varieties are easier – look for red leaves with green veins
- The probability that neighboring vines are infected are quite big, so depending on your budget I would recommend that they too be marked
- These vines must be cut down and a herbicide must be applied to the trunk wound to kill off the root system where surviving mealy bugs can chill.
- Try to remove as many roots as possible
- Once removed, let the soil chillax till next year when you plant your new, virus free vine
- Planting the new vines
- This is not an easy task. Careful planning and execution is needed
- Vines must be ordered a year in advance, preferably from a nursery that offers blue band vines (registered virus free)
- Make a proper planting hole. Mix the soil with compost or pelleted organic fertilizer.
- If you can, use a old wine box with both ends open, put that in the planting hole and plant the vine in the middle of the box. This will prevent neighboring roots to suppress the young vine. The box will rot in about 4 years and you will have a healthy vine
These processes must become part of your monthly planning. Work this in there, execute it and you will see your vines prosper, grow old, produce the crop they are supposed to and bless you with wonderful wine.
Industry progress
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