Thriving coffee seedlings treated with foliar fertilizers, symbolizing disease control and plant health.

Coffee Plant SOS: Can Foliar Fertilizers Beat Phoma Leaf Spot?

Jordan Keane in Science & Nature July 2025 • 4 min read.

"Discover how innovative fertilizer strategies are helping coffee farmers combat disease and boost yields sustainably."

For coffee growers, Phoma leaf spot is a persistent headache. This fungal disease, caused by Phoma tarda, leads to leaf lesions, branch dieback, and fruit rot, significantly impacting crop yields. In some cases, farmers face losses ranging from 15% to 43%.

Traditionally, Brazilian coffee cultivars have been protected by periodic applications of chemical fungicides. However, growing consumer demand for residue-free food is pushing farmers to explore alternative, more sustainable disease management strategies.

This article delves into the findings of a recent study investigating the effectiveness of foliar fertilizers in managing Phoma leaf spot. We'll explore how these fertilizers, packed with macro- and micronutrients, can bolster coffee seedlings' natural defenses and reduce the reliance on synthetic chemicals.

Foliar Fertilizers: A Nutritional Approach to Disease Control

Thriving coffee seedlings treated with foliar fertilizers, symbolizing disease control and plant health.

The research focused on several foliar fertilizer formulations, each designed to provide specific nutritional support to coffee seedlings:

The fertilizers included:

Fmm: A blend of macro- and micronutrients (10% N, 4% S, B, 5% Fe, and 5% Zn)
Fcm: Cobalt and molybdenum (2% Co and 3% Mo)
FMn: Manganese phosphite (30% P2O5 and 9% Mn)
Combinations: FMn+Fmm, Fcm+Fmm, and FMn+Fcm+Fmm

These treatments were compared against a control group (no treatment) and a group treated with a boscalid fungicide, a common synthetic option. The researchers then monitored disease severity, chlorophyll content, photosynthetic rate, and key defense enzyme activity.

The Verdict: A Promising Path to Sustainable Coffee Farming

The study's results indicate that foliar fertilizers, particularly FMn+Fmm and Fcm, can effectively reduce Phoma leaf spot severity in coffee seedlings. These treatments boosted the activity of phenylalanine ammonia-lyase (PAL), a key enzyme in plant defense. The FMn treatment also led to the highest increase in photosynthetic rate, indicating improved plant health and vigor.

While the synthetic fungicide still provided the highest level of disease control, the foliar fertilizer treatments offer a compelling alternative for farmers seeking to reduce their reliance on chemicals. By providing essential nutrients and stimulating natural defense mechanisms, these fertilizers can contribute to a more sustainable and environmentally friendly approach to coffee production.

Further research is needed to optimize fertilizer formulations and application strategies. However, these initial findings suggest that foliar fertilizers hold significant promise for managing Phoma leaf spot and promoting the long-term health of coffee plantations.

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This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1111/jph.12745, Alternate LINK

Title: Foliar Fertilizers For The Management Of Phoma Leaf Spot On Coffee Seedlings

Subject: Plant Science

Journal: Journal of Phytopathology

Publisher: Wiley

Authors: Manoel Batista Da Silva Júnior, Edson A. Pozza, Mário L. V. Resende, Pedro M. R. Júnior, Bruno H. G. Costa, Camila A. Carvalho, Alexandre R. M. Resende, Deila Magna Dos Santos Botelho

Published: 2018-07-17

Everything You Need To Know

What is Phoma leaf spot, and how does it impact coffee plants?

Phoma leaf spot, caused by the fungus Phoma tarda, is a disease that affects coffee plants. It leads to leaf lesions, branch dieback, and fruit rot, which can significantly reduce crop yields. Farmers can experience losses ranging from 15% to 43% due to this disease. Understanding the lifecycle and spread of Phoma tarda is crucial for implementing effective control measures.

How do foliar fertilizers help coffee seedlings fight Phoma leaf spot?

Foliar fertilizers, such as Fmm (a blend of macro- and micronutrients), Fcm (cobalt and molybdenum), and FMn (manganese phosphite), are designed to provide coffee seedlings with essential nutrients directly through their leaves. This nutritional boost can enhance the plants' natural defenses and reduce the severity of Phoma leaf spot. These fertilizers offer a sustainable alternative to traditional chemical fungicides by promoting plant health from within.

Which foliar fertilizer treatments have proven most effective against Phoma leaf spot, and how do they compare to traditional fungicides like boscalid?

The combination of FMn and Fmm, as well as Fcm alone, has shown effectiveness in reducing the severity of Phoma leaf spot in coffee seedlings. FMn treatment also significantly increased the photosynthetic rate, indicating improved plant health and vigor. These treatments work by boosting the activity of phenylalanine ammonia-lyase (PAL), a key enzyme in plant defense. While boscalid fungicide, a common synthetic option, can be effective, these fertilizer combinations offer a more sustainable approach.

How do foliar fertilizers boost coffee seedlings' natural defenses against diseases like Phoma leaf spot?

Foliar fertilizer treatments bolster the plant's own defense mechanisms, particularly by increasing the activity of phenylalanine ammonia-lyase (PAL). PAL is an enzyme crucial in plant defense responses. By enhancing PAL activity, the coffee seedlings become more resistant to Phoma tarda, reducing the impact of the disease. This approach aligns with a broader trend toward sustainable agriculture, where promoting plant health is prioritized over solely relying on chemical interventions.

What are the broader implications of using foliar fertilizers for coffee farming?

The findings suggest a promising path toward more sustainable coffee farming practices. By strategically using foliar fertilizers like FMn, Fmm, and Fcm, coffee growers can reduce their reliance on synthetic fungicides while still effectively managing Phoma leaf spot. This approach not only benefits the environment but also addresses the growing consumer demand for residue-free food. Further research and field trials are needed to optimize the application of these fertilizers and fully understand their long-term effects on coffee plant health and yield.