Biorational Pest Control



The most important aspect of plant health care is to improve and maintain growing conditions and management with intelligent landscape and farm design, compatible plantings, good soil and water management, regular inspections, anticipation of potential plant problems, and utilizing early intervention with bio-rational methods and materials when needed. With intelligent plant management and soil fertility, resistance to pest infestations and disease infections can be enhanced, therefore reducing need for pesticides.


  • Synthetic pesticides are manufactured in a laboratory and marketed by a chemical company. Synthetic pesticides are generally grouped into similar chemical classes such as neonicotinoids, organophosphates, pyrethroids, or carbamates.
  • Natural and botanical pesticides like rotenone, pyrethrum, nicotine, and neem extracts are products of living organisms. Often they are chemicals that plants use to protect themselves from parasites and pathogens.
  • Inorganic pesticides like borates, silicates and sulfur, are minerals that are mined from the earth and ground into a fine powder. Some work as poisons and some work by physically interfering with the pest’s metabolism, reproduction, and/or feeding.
  • Bio-rational pesticides are those synthetic, organic, or inorganic pesticides that are both low toxicity and exhibit a very low impact on the environment. They also have minimal impact on species for which they are not intended. Bio-rational pesticides include botanicals (plant-based), horticultural oils, insecticidal soap, herbicidal soap, microbials (biological controls and biological fungicides).  See BIOPESTICIDES below.

 Reduced Risk Pesticides, as defined by the US EPA, are those commercially available products that are “viable alternatives to riskier conventional pesticides such as neurotoxins, carcinogens, reproductive and developmental toxicants, and groundwater contaminants.”

 According to the EPA reduced risk pesticides offer:

Low impact on human health

Lower toxicity to non-target organisms (birds, fish, plants)

Low potential for groundwater contamination

Low use rates

Low pest resistance potential

Compatibility with Integrated Pest Management (IPM) practices


A bio-rational approach to pest and disease management can utilize reduced risk materials, and also methods of application that reduce applicator and environmental exposure.

Hydraulic spraying of the foliar canopy:  Reduced risk pesticides can be sprayed onto the foliar canopy of the tree for a contact kill of a pest, or as a repellent, anti-feedant, reproductive disruptor.  Some systemic pesticides can be absorbed through the leaves for translaminar movement through the leaf or translocation throughout the plant tissues, so that when a pest sucks the tree sap or chews the leaves, it ingests the pesticide.

Soil drench and Sub-surface soil Injection: Soil applications use water soluble fertilizers or pesticides applied to the soil surface, or injected with hydraulic equipment below the soil surface. These systemic materials are then absorbed by tree roots and dispersed throughout the tree through its vascular system.

Trunk (Stem) Injection: Trunk injection is a closed system method which involves drilling into the tree trunk and injecting a pesticide or fertilizer directly into the conductive tissue of the tree where it is taken up and translocated throughout the tissues.

Basal Bark Application: This technique uses a specialized water-soluble systemic solution, mixed with a bark penetrating surfactant, sprayed on the tree trunk for absorption through the bark, into the tree conductive tissue.

With intelligent plant management and use of bio-rational methods and materials, soil and plant health can be maintained with minimal use of pesticides and exposure to harmful substances.


This is a simplified description. There is much more to the classification of pesticides, toxicity, modes of action and adjuvants.

See the book “The Safe and Effective Use of Pesticides” a UC publication.

See also: