Dealing with insect and mite pests in organic production systems can be challenging primarily due to the limited availability of pest control materials (in this case, insecticides and miticides).It is important to implement a holistic pest management strategy that involves scouting (using colored sticky cards), cultural practices (sanitation, and water and fertility management), physical controls (screening greenhouse openings), and biological controls (parasitoids, predators, and entomopathogenic nematodes). These strategies should be executed in conjunction with applications of pest control materials. Furthermore, minimizing the use of pest control materials to deal with insect and mite pests is always recommended in order to avoid potential problems associated with resistance and phytotoxicity (plant injury).

There are a number of pest control materials available for use in organic production systems including the active ingredients Bacillus thuringiensis, Beauveria bassiana, potassium salts of fatty acids, azadirachtin, neem oil, pyrethrum, spinosad, and horticultural oils (e.g. petroleum, plant, and fish-based). Nearly all of these pest control materials share the following characteristics: 1) short-residual activity, 2) subject to ultra-violet (UV) light degradation and rainfall, 3) primarily active on the immature stages of insect and mite pests, 4) generally less  harmful to natural enemies such as parasitoids and predators, 5) low mammalian toxicity, and 6) may take longer to kill target insect and/or mite pests compared to conventional pest control materials. Below are a number of characteristics associated with pest control materials that may be used to regulate insect and mite pest populations in organic production systems. One or two trade names are provided for each category as examples; a complete list of approved products is available at www.omri.org.

Bacillus thuringiensis (soil-derived bacterium)
  •Products: Bacillus thuringiensis spp. kurstaki or Btk (Dipel and other trade names) and B. thuringiensis spp. israelensis or Bti (Gnatrol).
•Btk is active only on caterpillars whereas Bti is active only on fungus gnats.
•Insects must consume the material in order to be affected.
•In general, more active on young larvae than older larvae.
•Subject to ultra-violet light degradation and rainfall.
•May indirectly impact natural enemies by reducing the quantity of hosts.

Beauveria bassiana (entomopathogenic fungus)
•Products: Mycotrol and Naturalis.
•Insects are affected either by consuming the fungus or the fungus penetrates the cuticle.
•Speed of kill depends on the number or concentration of spores contacting the insect, insect age, and environmental conditions (temperature and relative humidity).
•Active on soft-bodied insects such as thrips, whiteflies, aphids, and caterpillars.
•Susceptible to ultra-violet light degradation.
•Multiple applications are typically required.
•In general, active on young larvae more so than older larvae.

Potassium salts of fatty acids (insecticidal soap)
•Products: M-Pede.
•Kills target insect (and mite) pests by disrupting the cuticle resulting in desiccation.
•Contact only, so thorough coverage of all plant parts is essential. Also, has short residual activity.
•Primarily effective against soft-bodied insect and mite pests such as aphids, whiteflies, spider mites, and mealybugs.
•“Hard” water or water with high amounts of calcium or magnesium may reduce effectiveness.
•Harmful (=phytotoxic) to plants if used too often.
•In general, not indirectly (sub-lethal) toxic to natural enemies.

Azadirachtin
•Products: AZA-Direct, Neemix
•Derived from the neem tree, Azadirachta indica.
•Multiple mechanisms of action: insect growth regulator, antifeedant, sterilant, and oviposition inhibitor.
•Primarily active on caterpillars; more so than other insect and mite pests.
•Multiple applications are typically required.
•Subject to ultra-violet degradation and rainfall.
•More effective on young (larvae and/or nymph) stages than eggs and adults.
•Tends to be more effective at temperatures above 70°F.

Neem oil
•Products: Triact and Organica (neem oil and soap).
•Active ingredient: clarified hydrophobic extract of neem oil.
•Works by suffocating or blocking the breathing pores of insect and mite pests. 
•Primarily active on soft-bodied insect and mite pests such as aphids, spider mites, whiteflies, mealybugs, and scales.
• May be phytotoxic if applied too often.
•May directly (lethal) affect natural enemies.

Pyrethrum
•Product: Pyganic.
•Pyrethrum is the generic name; pyrethrins are six active constituent compounds derived from chrysanthemum flowers.
•Works by contact only, so thorough coverage of all plant parts is critical. Also, has very short residual activity.
•Highly toxic to bees.
•Susceptible to ultra-violet light degradation.
•May be active on a broad range of insect and mite pests including true bugs, caterpillars, flies, aphids, and whiteflies.
•Final spray solution should be buffered to a pH of 5.5 to 7.0.

Spinosad
•Product: Entrust.
•Active ingredient: Saccharopolyspora spinosa.
•Composed of spinosyns A (85%) and D (15%).
•Fast-acting, and has both contact and ingestion activity.
•Has translaminar properties. This means that the material penetrates leaf tissues and forms a reservoir of active ingredient within the leaf thus providing protection even after spray residues have dried.
•Active on caterpillars, thrips, flies, and certain beetles.
•Any wet residues may directly or indirectly harm certain natural enemies, particularly parasitoids.

Horticultural oils
•Products: PureSpray Green, Organocide.
•Types: Petroleum (or mineral), plant, and fish-based.
•Works by preventing normal exchange of gases or by suffocation via blocking openings in the respiratory system.
•Active on most life stages of insect and mite pests including eggs, larvae or nymph, and adult.
•Primarily effective against soft-bodied insect and mite pests such as aphids, spider mites, scales, thrips, whiteflies, and mealybugs.
•Contact only, so thorough coverage of all plant parts is important; however, may be phytotoxic if applied too often or if applied during conditions of high humidity (above 75%).
•May be directly (lethal) harmful to natural enemies.

As always, the primary means of avoiding substantial problems with insect and mite pests when growing crops organically is to implement a variety of different management tactics including scouting, cultural, physical, and/or biological. Relying solely on insecticides and miticides will, on most occasions, make it difficult to prevent insect and mite pest outbreaks.   

Raymond A. Cloyd is Associate Professor and Extension Specialist in Ornamental Entomology/Integrated Pest Management at Kansas State University. He can be reached at rcloyd@ksu.edu