How Kona Coffee Is Affected by CLR

If you follow Kona Coffee, you have most likely heard about Coffee Leaf Rust (CLR). 

Coffee Leaf Rust (CLR) is a devastating fungus that has impacted coffee crops worldwide for centuries. The disease is caused by the Hemileia vastatrix fungus, which infects coffee trees by attacking the leaves. The first signs of CLR appear as little yellow spots on the leaves. On the underside of the leaf are lesions that eventually break open, releasing spores that spread to other leaves, eventually causing defoliation. Once leaves begin to drop, the trees can no longer photosynthesis effectively.

CLR didn't appear in Hawaii until 2020, first in Kona and then spreading to the rest of the island and, eventually the entire state. This year, the impact was felt even more keenly - with a reduction in harvest yields by as much as 60%. Sadly, many farmers lost their whole orchards, with trees defoliated to the point that they were forced to stump their trees in an attempt to "reset" the plants.

What Can Be Done?

At the recent Kona Coffee Syposium hosted by the Kona Coffee Farmer's Assocation, CLR was the number one topic of concern at the event. We heard speakers on an arrange of topics, from soil health and farm management to the latest in scientific research being done to identify the best methods for managing the CLR pathogen. Hawaii Department of Agriculture is spearheading these efforts, with a number of fungicide trials and studies to determine the most effective farm management methods.

Kona coffee farmers Steve & Joanie Wynn inspect their orchard regularly for signs of coffee leaf rust.

In a nutshell, here are the takeaways from this industry educational event:

Monitor:

Growers need to be vigilant as they manage their fields, looking for signs of CLR and acting quickly at the first signs to address the problem.

Orchard Management:

CLR thrives in warm, wet, and humid conditions, so ensuring the tree has access to adequate sunlight and airflow prevents it from taking hold. Pruning, suckering, weed control, and removing old or dying trees will help support tree health and make it less attractive to CLR pathogens. Pruning and weed control is also a way to remove competitors to the trees' vital nutrients. These farm management practices contribute to the overall hygiene of the trees and are considered an essential part of maintaining optimum tree health.

Good orchard sanitation practices are helpful for other pests such as the Coffee Berry Borer Beetle (CBB) and the white moth that attacks the tree trunks.

Nutrition:

Soil and foliar health are vital to support trees' natural ability to fight disease. Fertilizers can be added to achieve optimum pH levels and add nutrition to the growing environment. Foliar sprays can also protect and improve leaf retention. Though costly, these additives are another key contributing factor to maintaining trees that are thriving, supporting them to produce the best crop yield.

Treatment:

Fungicide sprays have proven to be the most effective in treating CLR. There are a variety of methods currently being studied to determine what is the most effective. Some are preventative, others inhibit spore germination and disease spread.

Unfortunately, these management tactics treatments are costly in terms of both the chemicals employed and the labor used to implement them. Overall, experts advised that Kona coffee growers should plan to spend 3-10% of profits to control CLR. 

In conclusion, the best way to manage and prevent CLR is through a combination of careful monitoring, farm management practices, nutrition, and treatment. 

Once a pathogen like CLR takes hold, it is virtually impossible to remove it entirely.  That said, this disease can be managed with diligence and knowledge, though not eradicated entirely.  

We encourage all Kona coffee farmers to stay informed about the latest research and collaborate with researchers for more solutions to this threat. Our hope is that by continuing to work together, we can help preserve Kona's treasured coffee legacy for generations to come. Thank you!