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How 4 North American Grape Vine Diseases Destroyed the Vineyards of Europe

The History of French Wine Law - Part I

It’s the middle of the 19th century, wine is THE most traded commodity in the world. It was not the arms trade (as it is today); it was wine. Then 4 North American grapevine diseases cross the Atlantic and destroy most of the vineyards of Europe – the epicenter of wine production (and still is today). The diseases kill the vineyards and causes an economic depression felt throughout the world.

In this post, we’ll discover those 4 diseases that ravaged the wine world: powdery mildew, the phylloxera louse, downy mildew and black rot. In the process, we’ll uncover what they are, what they do to the vine, how it spreads and how we can prevent them.

What’s amazing to me, is that these 4 diseases are still feared today. So if you are wanting to plant a vineyard, you’d best pay attention to the lessons of the past.

Further, if you are looking to expand on this topic, take a look at the other posts in this series. In part 2, we take a look at the devastating effects on the peasant class during the ‘dark ages’ of wine. Finally, in part 3, read about the History of French Wine Law as it unfolds in Bordeaux, Champagne and Southern France.


The backdrop...

Improved transportation routes such as railways increased worldwide demand for wine

Imagine living during the Industrial Revolution: a time of progress, technology, speed and immense changes to the social order. Railways and steamships connect goods quicker than ever to markets around the entire globe.

Previously, society was rigid and simply divided. There were peasants and there was the nobility. But during this time, two other classes emerge; the middle class of small business owners, doctors, and scientists and an upper class of wealthy entrepreneurs such as factory owners.

Not only would this new wealth require a much larger working class of domestic workers to service them, it meant that wine was affordable to a much broader population.



So, new codes form to govern social behaviour. The middle classes create etiquette rules that govern how to dress, give a dinner party and pay social calls. What’s more, wine becomes a central feature of middle class affluence.

These thriving middle and upper classes create unfettered consumer demand for European wines. At the same time, international trade routes connect wines at speeds never before imagined to relentlessly growing markets.

[Want to know the effects of the economic crashes on the peasant class? Read this post here]


Conversely, inside France, trade routes were still cumbersome and slow. 

Nevertheless, in Western Europe farmers rush to meet the demand of the drinking habits of the rising middle class. It stimulates a planting frenzy that ensues throughout France, Italy and Spain. 

In fact, France, Italy and Spain are still the largest wine producers in the world.

And then, the wine market crashes. Not just once, but many times.


How 4 North American Grapevine Diseases Destroyed Vineyards in Europe

So why during the golden era of wine trading, did the market crash?

The wine market crashes of 1845, 1863, 1882 and 1885.

At this time, wine growth during the 19th century is primarily fuelled by improved trade routes that bring goods to markets around the world.  Ironically, it is equally the cause of it’s demise. 

The journey at this time, only takes a short 8 or 9 days as opposed to the 6-14 weeks of before. Therefore, grapevine diseases and lice from North America survive the journey back –  and European vines can’t withstand them. 

So, here are the 4 North American grapevine diseases that destroyed the vineyards in Europe.


The 4 North American Vine Diseases that Destroyed Europe's Vineyards...

1. Powdery Mildew - 1845

What is it?

Powdery mildew (öidium in French; uncinula necator in Latin; Erysiphe necator to specify the disease specifically in grapevines and now more widely known as E. necator). This grapevine disease attacks the green parts of vines. It gets it’s name from the spores that multiply into powdery looking cobweb-like growths.

How does it spread?

Winds will swiftly spread the disease. Found in England in 1845, it will cross the Atlantic to France by 1847. This is the first grapevine disease that will destroy the vineyards of Europe.


powdery mildew's cobweb like spores - a grapevine disease that destroyed vineyards in Europe
powdery mildew disease destroyed vineyards in Europe -"Papaya (Carica papaya): Powdery mildew" by Plant pests and diseases is licensed under CC PDM 1.0

It spreads by 2 main mechanisms. First it spreads easily by wind in its ‘conidia’ powdery form, where it can later overwinter in the vine. If powdery mildew infects the buds, the shoots that grow in the spring (called flag shoots) will have the cobweb looking ‘conidia’ all over and spread it to the rest of the green parts of the plant as it grows.

Second, there is a sexual form of powdery mildew called ‘cleistothecia’. These are black spherical bodies that overwinter in the vine bark. These are particularly dangerous as it allows the fungus to reproduce. In this situation, powdery mildew has the ability to build a resistance to fungicides.

What does it do?

Unlike other fungal diseases, powdery mildew can germinate in dry conditions. In fact, rain can actually hinder it’s development. Still, it particularly loves damp, shaded areas. The shade part being most helpful in creating conditions that are good for powdery mildew.

Powdery mildew decreases both the amount of wine made from the plants as well, the quality is terrible. When the grapes are infected, berries will split, exposing juice to unwanted oxidation and makes mouldy tasting wine. It also reduces the colour and the amount of wine that can be made.

Powdery mildew will cause the disasterous vintage of 1854 – France’s smallest since 1788. In fact, it’s so damaging even today that famous wine scientist Jamie Goode considers E. necator to be the wine world’s biggest problem.

What is the cure?

Fortunately, the gardener who first disovers powdery mildew in England also notices the cure – a mixture of sulphur, lime and water – and sprays it on the vines. After 1854, this solution is widely accepted (and still used today).

Sulphur must be sprayed evenly on all green areas of the vine and must be applied weekly during peak times (end of June in Northern Hemisphere and at Christmas in the Southern Hemisphere . We now know that E. necator doesn’t like UV light. So exposing grapes to sunlight and air by pruning helps to prevent it’s spread.

Unfortunately, preventative measures against powdery mildew are not as effective as they are against downy mildew (see below). Spraying will be necessary.

Organic or natural treatments

However, using too much sulphur and lime in solution (called Bordeaux mixture) over long periods is known to cause adverse affects in the soil. Therefore, viticulturalists looking for less harmful sprays can use a mixture of milk and water. If you are a certified organic producer, use organic milk. 

Most recommend a 40/60 ratio of milk to water and spray accordingly.

2. Phylloxera - discovered in France in 1863

What it is and what it does?

Phylloxera is a louse (plural: lice). In fact this phylloxera is famously known as the Great French Wine Blight. It has three stages to it’s life cycle and over all three can attack both the roots and the leaves (leaf galls only forming on American vines).

First, the females which are barely visible to the naked eye, feeds off the roots. Over a summer, 7 generations build producing eggs and feeding. It feeds off the roots of vines causing it to bleed out the sap causing deformities and eventually kills the plant.

The eggs also produce ‘crawlers’ that move to other roots. The disease fans out in a circular form around the original infection site. Furthermore, they can move up the plant and be blown to other areas by the wind.  So just as France’s vineyards recover from powdery mildew, this bug will come along.

a close up of the phylloxera louse known as the Great French Wine Blight - a grapevine disease that destroyed vineyards in Europe
Phylloxera Vastatrix or 'the Devastator', a grapevine disease that destroyed most of the vineyards in Europe - "Phylloxeria Plant Louse" by treegrow is licensed under CC BY 2.0

How it spreads?

Grapevines were already travelling between the Americas and Europe over centuries at this point. Yet advanced steamships with improved engines made this trip at record breaking speeds previously only dreamed of. Voyages in wooden ships using masts and sails took many months and the lice would die on the long transatlantic voyage.

Today, it is still most commonly spread by rootlings or one-year-old dormant plants but can be spread through soil stuck to farming equipment or through foliage on trimmers and harvesters.

The French discover the bug in 1863, making it the second grapevine disease to destroy Europe’s vineyards. Slowly through the decades, phylloxera will crawl its way throughout Europe. Originally called Phylloxera Vastatrix (the devastator), it is now called Dactylasphaera Vitifolia.


Phylloxera galls on a vine leaf. Phylloxera causes one of the wine crashes in the 19th century. Online Wine Course

Image of a grape leaf that has been attackged by phylloxera lice. Originally called Phylloxera Vastatrix ‘the devastator’, it’s known as the Great French Wine Blight. These galls form mostly on American vines, on French hybrids and only moderately on the European species Vitis Vinifera during humid conditions. In European grapevines, the female aphid that attacks the roots is barely visible. However, the rootstocks they attack will have deformities.

Truly, the social and economic effects of phylloxera are massive and can be compared to the failed potato harvests of Ireland. In France alone, that bloody bug will annihilate 2.5 million hectares of vineyards!

In fact, riots will ensue in Burgundy. Lynch mobs will attack the teams sent in to spray the vines and soldiers are sent in to surround and protect the famous Meursault vineyard.

Imagine the trauma of watching your neighbour’s entire vineyard die and then waiting and watching as that bug comes for your own.

The treatment and possible cure?

Eventually, scientists discover they can graft French vines onto American rootstocks and save their plants. American vines form a scab over the feeding area so the vine doesn’t bleed to death and survives.

But, it will take some time to implement this change, to find rootstocks that will work in French soils and…to convince the French. Indeed, Burgundy will outlaw this solution until 1887, almost 20 years after it’s arrival there.

3. Downy Mildew or Peronspera (introduced in France sometime before 1882)

What is it?

While the cure for phylloxera is fully underway, a new disaster will strike. Likely carried on the rootstocks sent from North America to prevent phylloxera, a fungus called downy mildew will slip into the country.

By 1882, the disease is already widespread throughout France. It’s the third in a row of grapevine diseases that destroy Europe’s vineyards. In fact, downy mildew is one of the most economically significant grapevine diseases for decades to come, producing many record low-yielding vintages up until 1969.

What does it do?

Downy mildew attacks the green parts of the vine where yellowish patches appear on the leaves (called oil patches) and it delays ripening. In fact, it can cause the leaves to fall off completely – thereby halting photosynthesis entirely. Furthermore, downy mildew eventually decreases the winter hardiness of the vines.

Affected berries will turn either a dull green or reddish-purple colour. They may then fall from the cluster.

You can’t make much wine with what’s leftover and the resultant wines are weak.

Downy Mildew, a North American grapevine disease destroyed vineyards in Europe
Downy Mildew fungus, considered a grapevine disease that destroyed vineyards in Europe - Plasmopara viticola a1 (4) by Jerzy Opiola cc BY-SA 4.0

How it spreads, the treatment and cure?

This fungus is generally spread during cool, wet vintages and can hit at any time of the year. The oil patches are actually spores that are spread by winds.

Copper sprays are the first effective treatment. However, copper buildup in soils has proven to be bad for soil health. So now in the EU, copper treatments are legally controlled and can only be 3 kg/ha/yr for organic vineyards to a maximum of 6 kg/ha/yr for others (these are based on the average applications over a 5 year period and the amounts allowed depend on the climate zone of the vineyard).  For organic vineyards, expensive fungicides are also used. Visit this post for a recent study of the effectiveness of copper alternatives and the most cost effective ones to use.

Unlike with powdery mildew, prevention methods against downy mildew are very effective. These include maintaining low yields, choosing the right cover crop, and make sure the foliage dries quickly after rain by removing leaves, tying up branches and so on.

4. Black rot - 1885

Black rot as seen on grapevine leaves, a grapevine disease that destroyed vineyards in Europe
Black Rot or "Guignardia bidwellii 08" -North American grapevine diseases destroyed vineyards of Europe by Danile Molitor CC BY 2.0

What is it?

American rootstocks also brought black rot fungus to Europe (Guignardia Bidwelli).

In fact, right now it’s currently contaminating vines in Europe.

How it spreads what does it do?

It’s spread by mild, wet temperatures and can kill upwards of 80% of your crop. It attacks leaves, shoots, and berries. Early signs show tan coloured spots on the leaves (as shown on the left). Later, black spots will form. This schmo is such a swindler as grapes will appear to be normal until mid-summer when berries will turn black, shrivel and turn into ‘mummies’.

when black rot attacks grapes they become mummies
when black rot attacks grapes they become mummies

Treatment and the cure?

This is the bane of organic growers because of the limited ways to control it. Infected mummified berries must be painstakingly removed (along with parts of the cane) and burned. Otherwise, the spores will survive over winter and come back in the spring.

It takes merely 7 hours in warm, wet conditions for black rot to spread!

For non-organic growers, fungicides need to be applied in the spring continuously until the fruit ripens.


4 North American grapevine diseases destroyed the vineyards in Europe and caused the complete annihilation of the wine market in the 19th century. At this time, steamships and trains very quickly brought wine from France, Italy and Spain to growing new markets the world over.

Then after European wine was delivered to North America, grapevine diseases piggybacked on organic material travelling back to Europe.

Steamships could now finish the journey in just 8-9 days. So the diseases could survive the journey.

Furthermore, these fungi and lice were developed in isolation of European vine species which had no defence mechanisms to protect themselves from them.

So even today, viticulturalists spray against powdery mildew with either a mixture of sulphur, lime and water (Bordeaux mixture) or of milk and water in solution (the natural choice). Moreover, precautions such as grafting vitis vinifera vines onto specific American rootstocks is still advised to prevent the phylloxera louse from killing your vineyard. In fact, specific rootstocks are grown in nurseries to be resistant to many diseases – so know where you are planting and the disease pressures you will face before you plant! Choose rootstocks accordingly. 

There are also ways to prevent downy mildew that are very effective. These include maintaining low yields, choosing the right cover crop, and make sure the foliage dries quickly after rain showers by removing leaves, tying up branches and so on. 

Finally, the only organic or natural solution to contain black rot is to painstakingly pick all of the rotting vegetation and burn it before the spores spread. However, you’d best just spray it with organic fungicides because if you miss any of it, you’ll have a bigger mess on your hands the following year!


“Cooperation and Conflicts: Institutional Innovation in France’s Wine Markets, 1870-1911” by James Simpson. In The Business History Review Vol. 79, No. 3 (Autumn, 2005), pp. 527-558. Published by the President and Fellows of Harvard and found on

“Grape Phylloxera Pest Management Program for Grape Series” by Todd Leuty for the Ministry of Agriculture, Food and Rural Affairs of Ontario.

“Wine science: powdery mildew, the wine world’s biggest problem.” by Jamie Goode, March 27, 2020

Research Center website

“Revolt of the Languedoc Winegrowers” in Wikipedia, the Free Encyclopedia. Retrieved on February 10, 2020.

“The Oxford Companion to Wine” Edited by Jancis Robinson and Julia Harding. Oxford University Press, 2015. Entries on “France”, “Powdery Mildew”, “Black rot”, “Downy Mildew”, “Phylloxera”, “Vitis Vinifera”

“The Changing Attitudes and Values During the Industrial Revolution” by Morgan Ashli, last updated December 1, 2011, published on Prezi.

“The Great French Wine Blight” in Wikipedia, the Free Encyclopedia. Retrieved on January 30, 2020.

“The Great French Wine Blight” by Pat Montague and published in Wine Tidings No. 96, July/August, 1986.

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