Growers can manage plant nutrition to achieve resistance to pests and diseases
The presence of pests and diseases is often a symptom of deeper problems in plant health. While agricultural practices have traditionally responded to these issues with pesticides and other interventions, a growing body of evidence supports a different approach: building plant health to prevent susceptibility.
Healthy plants, with the right nutrition, have natural defenses against many pests and diseases. This concept is more than theoretical — it has practical applications on the farm, allowing growers to foster robust, resilient crops.
Understanding Plant Immunity
Plant immunity can be understood as a progressive journey through four distinct levels, each tied to specific physiological processes and nutrient requirements. As plants ascend each level, they gain new immunity, beginning with soil-borne fungal pathogens and advancing toward resilience against more complex threats, including insects and even viruses.
Level 1: Complete Photosynthesis
The foundation of plant health begins with complete photosynthesis. This stage is critical, as it enhances the plant’s capacity to produce sugars — vital energy sources that power growth and immune functions. A plant photosynthesizing at full capacity can boost its sugar production by as much as 3-4 times, a shift that can be easily monitored in the field with a refractometer to measure Brix levels. When plants photosynthesize efficiently, their Brix readings can leap from an average of 3-5 up to 12-15 or higher, indicating healthier, more robust energy production.
This increase in sugar quantity goes hand-in-hand with improved sugar quality. Plants at this stage produce complex carbohydrates instead of simple, non-reducing sugars, changing the profile of carbohydrates in the plant’s root exudates. This shift has significant implications for soil health, as complex carbohydrates support a microbial community in the rhizosphere that actively suppresses soil-borne fungal pathogens. At this level, plants become naturally resistant to soil-borne fungal diseases, such as verticillium, fusarium and rhizoctonia.
To achieve Level 1, plants need five critical minerals involved in photosynthesis: magnesium, nitrogen, iron, manganese and phosphorus. While magnesium and nitrogen are essential to chlorophyll synthesis, iron is crucial for chlorophyll assembly, and manganese is needed for water hydrolysis in photosynthesis. Phosphorus supports ATP production, which is essential for metabolizing the sugars generated.
Level 2: Complete Protein Synthesis
The second level of plant health centers on the synthesis of complete proteins. Plants at this stage efficiently convert nitrogen into complete proteins. At this point, plants become resistant to pests with simple digestive systems, such as larval insects and aphids, as these pests do not have the digestive capacity to handle complete proteins. Growers can monitor a plant’s protein synthesis through plant sap analysis to observe nitrate and ammonium levels, which should be close to zero if the plant is actively synthesizing proteins.
To advance to this level, plants need four essential minerals: magnesium, sulfur, molybdenum and boron. Magnesium, sulfur and molybdenum directly support nitrogen synthesis, while boron strengthens pest resistance by stabilizing cell walls.
Levels 1 and 2: Passive Immunity through Balanced Chemistry
Levels 1 and 2 provide passive immunity to pests and diseases. In these stages, plants create metabolic conditions so that they are no longer a food source, deterring infestations before they begin. This type of immunity relies on balanced plant chemistry and can often be achieved quickly with targeted nutrient applications. Growers aiming to reach these levels can apply the required minerals through well-formulated foliar applications to address common nutrient imbalances.
Level 3: Increased Lipid Synthesis
At Level 3, plants reach a state of energy surplus, allowing them to produce lipids, which they store as a waxy layer on their leaves. This layer becomes a physical shield, preventing airborne pathogens from penetrating plant tissues. Plants at this stage develop resilience against fungal and bacterial pathogens, including powdery mildew, downy mildew and rust.
Unlike Levels 1 and 2, which are largely chemistry-driven, Level 3 is influenced by the microbiome. As plants interact with soil microbes, they absorb complex nutrients, conserving energy that would otherwise go toward nutrient processing. This “prefabricated” nutrition enables sufficient energy reserves for lipid synthesis, creating the physical barriers essential for Level 3 immunity.
Level 4: Elevated Phytonutrient Synthesis
The pinnacle of plant health, Level 4, is marked by the production of plant secondary metabolites — compounds such as flavonoids, terpenoids and alkaloids. These phytonutrients act as potent defenses against a broad spectrum of threats, including chewing insects like beetles and, potentially, viruses. At this level, plants shift to active immunity, using biochemical defenses to repel pests and pathogens. To sustain this level of resistance, plants depend on a diverse and abundant microbiome, which stimulates systemic acquired resistance (SAR) and induced systemic resistance (ISR) within the plant.
Integrating the Plant Health Pyramid into Farm Management
The plant health pyramid provides a roadmap for growers to enhance crop resilience through balanced nutrition and microbiome management. By systematically progressing through each level, growers can support their plants in achieving new levels of health and immunity, reducing reliance on chemical interventions while producing healthier crops and contributing to a more sustainable agricultural ecosystem.
As growers strive to manage plant nutrition and microbiome health, they move beyond symptom treatment and embrace a holistic approach that supports plant resilience. This approach not only strengthens crop productivity but also promotes regenerative agriculture, where healthy plants, ecosystems and communities thrive together.
Jason Stoll is a senior agronomist with Advancing Eco Agriculture.
