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Economy

Plasmopara viticola, the oomycete responsible for downy mildew, is considered to be the most devastating grape pathogen to be known in North America and Europe.

This disease was originally observed in the United States in 1834 and has been most abundantly found in the northern and midwestern areas of the United States. Shortly after, the pathogen was introduced in European countries where it played a devastating role in the yield and production of their grapes, and consequently their wine. In 1878, the first cases of downy mildew were observed in France in the region of Lyon and also in Swizerland and Italy. Depending on the year, production of grapes in France has been estimated to be at a loss of 50% or more. Because of numbers and results like these, downy mildew has been considered the most devastating disease of a filamentous pathogen to affect European vineyards.

In the past few months (June 2015) there has been another violent attack of mildew on the grapevines in the Aquitaine region. Up to 60% of wine grapes have been infected on certain parcels and the vice president of the agriculture chamber, Patrick Vasseur, hasn't been underestimating the economic significance this could have since the wine production will evidently be affected. He calls the situation "exceptional" since "even the main branches are affected"

Serge Audubert, head of 3 castles in the region and owning a total of 24 ha, has been watching the effects on his land. On his 17 ha of château-laborde grapevines, in Saint-Médard-de-Guizières, 2 ha are severly touched. « the leaves, the branches, the grapes, everything is affected. We are going to loose at least 50% of the grapes on these 2 ha. » On the first of may, this vinyard observed a spot on a branch, nothing severe especially since the « Bulletin de santé du végétal » which came out a few days before clearly states that the conditions dont allow contaminations. As a precaution, Serge Audubert starts his preventive treatments on the 7th of may. On the 15th of May, the outburst starts, shicking the entire region: « I have been living here since 1987. I have never seen something like this. Informatics models were supposed to alert us when mildew evolution becomes dangerous. »

This year, mildew outburst are worrying vineyards in Aquitaine

A bit of History

In 2010, each hectar or grapevine had received around 16 chemical treatments (this number was 15 in 2006) and varies greatly between regions. Amongst the biological threats on grapevine, mushroom parasites are far ahead of insects and fungi (12 fungicides are used against 2 insecticides and 2 weedkillers). Over 95% of the fongicide treatments in 2010 were due to mildew and oidium, sicknesses that are favorized by rain, humidity and heat. They bring the global quality of the wine down by reducing it's composition in phenols and sugars

The risc of contamination on the leaves begin during the period where the floral buds and futur grapes are growing and lasts until the moment when the grapes touch each other. The sensibility period between oidium and mildew have common momments and vinyards don't heasitate to mix anti-mildew and anti-oidium solutions making the concentrations of these chemicals twice more concentrated in the grounds.

What are the problems with these treatments? Are they really efficient?

To have a really efficient treatment what would you need?

little comics ?

Our iGEM team has been following this year's effect of mildew closely reading the official vineyard mildew bulletins available on the vinopole website. We can see on the graph that there is a significant increase of mildew on parcels that haven't been treated with copper sulfate (TNT)whereas it's evolution on treated parcels seams to be more controlable. this proves that downy mildew is still a constant threat to vineyards.

Aquitaine is one of the regions where the risks are the highest at the moment. However, the weather conditions are positive for the fllowing weeks since pluviometry is expected to decrease, rendering the conditions unfavorable to the development of downy mildew.

iGEM Bordeaux: Contacting vineyards

to be continued ...

Read more at http://www.lavigne-mag.fr/actualites/bordeaux-enquete-sur-une-attaque-imprevue-de-mildiou-105408.html#JrRQ87eWGid6OCFo.99

Downy mildew requires optimum conditions to reproduce and infect. A warm, moist, and humid environment is required. Studies in Sicily have shown optimum time for oospore germination is between the end of February and the middle of March. With this understanding, if fungicides are used just before these conditions occur, and have proven to be efficient measures. Other methods include proper watering, and a good location where the plant can receive continual sunlight.