What is Leaf Rust and Why Should I Care?

If you love speciality coffee, as I do, then you and I have a problem. That problem is called leaf rust – AKA coffee rust, or Roya, or Hemileia vastatrix if you want to sound clever, and it’s a much bigger problem for coffee farmers than it is for us.

You will have heard of this issue I’m sure, but if you’re anything like me, you may have not understood previously what a really big deal it is. 

I was inspired to do some further about leaf rust in order to write this post, when I recently discovered that the bag of El Salvador Finca Argentine San Jorge Bourbon I had via my weekly coffee subscription from hasbean, was the last time this coffee would be available due to the disease. 

This farm had a devastating leaf rust issue in 2013 which lead to only 70 bags of coffee being produced, and they worked very hard to keep going after that. But their Bourbon plants are just no longer commercially viable, so that’s the end of this lovely coffee from this particular producer, which is such a shame. This lead me to spend some time researching this disease to see what it is specifically, and what issues it’s causing – and what I discovered shocked me!

Roya, Coffee Rust.

Photo Credit: The Coffee Trust


What exactly is leaf rust?

Fungus. Coffee Rust Isn't a Fun Guy...

Coffee Rust Isn’t a Fun Guy… Photo Credit: Dave McLear

I realise now that I’ve done a bit of research, that I had misunderstood what leaf rust was and how it works, now I know exactly what it is and how it operates, I can see what a huge issue it is. In fact now I know more about it, I’m really surprised that it hasn’t had an even worse impact that is has. 

What we know of as roya, or leaf rust, is a parasitic fungus. When you hear the word parasitic, you’ll probably initially picture parasites which effect humans and animals, such as tapeworms. What this disease has in common with things like tapeworms, is that it feeds of the host and leaves it depleted. Leaf rust causes leaves to drop, which means effected trees can’t properly photosynthesize in order to generate energy, so they grow smaller cherries and less of them. 

What it doesn’t have in common with most animal parasites though, is that being a fungus, is it’s an airborne parasite, it spreads via spores. Once it begins to infect a coffee plant, in as little as one to two days it can be ready to erupt with hundreds of thousands of spores which can spread not only to local crops, but depending on the wind the spores have been known to travel hundreds, and even thousands of Kilometres! 

Does it only effect speciality coffee?

No, all coffee is at risk. Although, in theory speciality coffee is effected more directly, because commodity coffee isn’t as dependent on specific varietals or on origin.

When you buy instant coffee, and whole bean or pre-ground coffee beans from supermarkets, the packaging may display the origin in some cases, but usually it’s just “coffee”. Even if it’s 100% Arabica, you don’t know if it’s Bourbon, Typica, Catuia, or whatever the case may be, and often it’s blends from various different origins. So the big coffee buyers who’re buying large quantities of coffee can shop around, and go for varietals which aren’t as effected by the problem. 

When you take into account the fact that there are many different hybrids that are not known for their quality but are known for their resistance to leaf rust, then on the surface it would seem that the commodity coffee industry is probably safe. If you’re buying tonnes of mixed Arabica beans from all over the world, mixing it with Robusta, and then roasting it in huge batches to within an inch of dust to be made into instant, some changes in the mix of beans I would assume make little difference to the resulting cup. The speciality coffee market is different, we’re not just buying coffee, we’re buying specific varietals or blends that have been very carefully grown, processed and then small batch roasted in order  to achieve specific taste profiles. 

The reason I say “in theory” though, is that in practice it seems that  leaf rust has the potential to effect all origins, and maybe even all varietals including the trees that are supposedly resistant, such as  Lempira and ihcafe 90 which have recently been effected.  See Coffee Leaf Rust Rears its Ugly Head Again in Honduras

What it means to coffee farmers.

No Leaf Rust - Happy Coffee Farmer

Photo Credit: Shared Interest

In a word, devastation. In the late 1800’s, Sri Lanka (or Ceylon as it was known at the time) saw the first recorded outbreak, and it went on to completely wipe out all coffee trees on the island!

In the outbreak that began in 2011/2012 in Central America, close to two million people lost their jobs, and it is estimated that a total of over $3 billion was lost.

As much as 50% of coffee trees have been lost in central American countries since this outbreak. See worldcoffeeresearch.org for more info. 

So it’s bad! 

What it means to speciality coffee lovers. 

When you see the numbers above, it’s no wonder that leaf rust is leading to price increases, and I think further increase in price is inevitable. The strength of the dollar against the pound has made a difference, and any other issues which make coffee more expensive to grow and to export also increase the price, but leaf rust in particular I would expect to continue to drive up the price. 

I actually think speciality coffee is cheap at the moment. Even at the higher end you’re probably looking at around 40-70 pence per cup depending on the brew method, and I don’t think you’ll even find a burger van that will sell you a polystyrene cup of instant this cheap ;-). In 10 or 20 years we’ll probably be reminiscing about the good old days when we could pay six or seven quid for a quarter kilo bag of amazing coffee, so we should make the most of it while it’s relatively cheap. 

Rising prices are a pain, but it’s not the worse that could happen. I realise that what happened in Sri Lanka was a long time ago and we have better technology now, but still – the worse case scenario may be extinction of the varietals we love, and a total reliance on the newest hybrid varietals have been created in the lab to be resistant to the current strain. I hope this never happens, and it probably won’t, I’m probably being over dramatic – but still, I see this as a very good excuse to enjoy speciality coffee as much as we can right now. 

Life is like a box of chocolates, so follow me on twitter, and visit the list of UK coffee roasters, and that’s all I have to say about that.



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