Sometimes the best approach to deterring insects is a good offense, for plants, that means keeping them healthy to shore up their defenses. Using plant nutrition as a weapon against the ongoing battle with insects is a preventative measure that can have long-lasting benefits. However, the key to using this integrated pest management (IPM) strategy is to maintain balanced nutrient levels. Disproportionate amounts of nutrients can have the unwanted effect of attracting insect populations instead of discouraging them.
Nutrients strengthen plant defense systems
Plant health influences the development of plant defense systems, both externally and internally. Mechanical barriers (e.g., cell walls, bark, etc.) are plants’ first line of defense against insects and disease. Without nutrients such as calcium, boron, zinc and silicon, these barriers would be weak, malformed and ineffective. Potassium and manganese are responsible for facilitating the release of defensive chemicals that help inoculate plants against attacks, a process known as systemic acquired resistance (SAR).
Effects of elevated nutrient levels
Elevated nutrient levels can be an invitation for insects to move in. Plants with excessive nitrogen levels, for example, can attract mites and aphids. High nitrogen levels also promote leafy, new growth. While this may seem like a good thing at first, the new foliage is often weak and straggly, making it the perfect target for insects.
In 2004, an article in Hortscience included the research results of a study on the effects of phosphorous and nitrogen levels in impatiens on Western flower thrips (WFT) populations. Researchers found that elevated phosphorus levels contributed to the accelerated growth of WFT populations.
Effects of low nutrient levels
Not enough of a good thing can cause problems too. An article published by the University of Florida extension service and authored by Timothy Spann and Arthur Schumann gives the example of the Asian citrus psyllid (Diaphorina citri), a vector for the devastating bacterial greening disease (HLB, Huanglongbin). This sap-sucking insect tends to gravitate towards yellow reflecting surfaces. Yellowing leaves is unfortunately one of the side effects of nitrogen, iron, potassium, magnesium, sulfur and zinc deficiencies.
Nutrient deficiencies also inhibit the production of a plant’s biochemical defense compounds. Potassium, boron and manganese are all necessary for the manufacture of defensive chemicals. Silicon influences the release of defensive compounds.
Keep plant nutrition balanced
Maintaining balanced plant nutrition is a good preventative measure for control of insects on plants, especially when combined with other integrated pest management practices. A good integrated pest management plan should include a balanced nutrition program based on crop type, plant lifecycle, and soil type.
Plant tissue analysis, combined with soil sampling, is the best way to accurately determine nutrient needs and diagnose problems. Since nutrient levels vary throughout the growing season, it may be helpful to test more than once a year. This is a good way to assess the effectiveness of fertilizer programs.
Sources:
Spann, Timothy and Arnold Schumann. 2010. “Mineral Nutrition Contributes to Plant and Pest diseases.” Gainesville, Florida: University of Florida Extension Service.
Williams, Kimberly and Yan Chen, Brent K. Harbaugh, Michelle L. Bell. 2004. “Effects of Tissue Phosphorus and Nitrogen in Impatiens walleriana on Western Flower Thrips (Frankliniella occidentalis) Population Levels and Plant Damage.” HortScience: 39(3):545-550.
Keyplex products have a patented blend of chelated micronutrients, enhanced alpha-keto acids and humic acid that helps fuel the energy requirements necessary for plant defense, growth and reproduction. Scientific data confirms that KeyPlex products elicit the production of defensive proteins (SAR), stimulates plants resistance to infection and aids in eradicating the damaging effects of environmental stresses.