Coffee Leaf Rust Experiment Update: One Month In

It has been just over a month since our initial sampling and treatments in the coffee leaf rust experiment that we are running here in La Unión (for the basics, read here). We have applied all organic treatments twice, all conventional treatments once, and have just finished looking at the data from one month in.

So what did we see?

Pedro must take precautions when
applying conventional treatments.

First, the conventional treatments: Although Alto 10 poses health and environmental hazards, it is hard to dispute its effectiveness. Of all the treatments, it is the only one that showed a decrease of rust incidence in all measured severity factors. Silvacur, the other systemic fungicide we are testing, showed a slowing of rust development, but didn’t show a decrease in the measured severity. Copper, the final conventional treatment, did not show significant initial results. However, this is logical, since copper is a preventative treatment whose effects are more likely to be seen over a longer time period.

Now, the organic treatments: When compared to the copper trial, milk whey showed a slight decrease in infected leaves, number of spots, and coverage area of rust. However, these decreases are relatively small and could still be attributed to random error. Sodium Bicarbonate showed a decrease in all areas when compared to copper. However, these decreases are also relatively small and could also still be attributed to random error.

And finally, the madrifol  treatment: Of all of the areas, this treatment is perhaps the most confusing. Upon initial analysis, it appears that there was a large increase in the number of rust spots in this plot. However, it was observed that two of the five treated plants appeared to have decreased rust incidence, while the other three showed significant increases in rust severity.

Martir applies organic
treatments to the plants.

We currently believe that this difference is due to differences in spacing—the two plants that showed a decrease have normal spacing while the three plants that showed an increase have closer than normal spacing due to planting irregularities on the test farm. This spacing difference appears to cause overlap of branches, leading to areas of higher infection.

We separated out the two trees that have normal spacing and found a decrease in both coverage and spot size, suggesting that madrifol may actually interrupt the development of rust spots, but only with proper spacing and pruning.

We are continuing to apply both organic and conventional treatments on the test farm. We will take the next sampling in another 30 days, and we will keep you updated on the progress of the experiment.