Article 4-1 Trimming Technique

Gardeners Guide to Proper Insecticide

The information contained in this article is designed to enhance the gardener’s knowledge of insecticides and for the gardener to attain the best results from applying them. Due to the variety of Insecticides available, in this issue, we will review botanical insecticides, the next issue we will review synthetic insecticides and our last article in this series will be on Integrated Pest Management. IPM is commonly referred to as Predator Mites.

Proper Use of Insecticide Sprays and Powders

First and foremost, identify the type of plant you are growing and the pest (use a 20X magnifier) that is causing the problem. If you are growing a food crop that will be ingested, be cautious of what type of insecticide you use, find one that is approved for food crops. In order for a insecticide to be sold as an insecticide it must have a Pest Control Product Registration Number, be sure that any products you use are registered, otherwise – user beware. The manufacturer of Registered Pest Control Products have had efficacy tests conducted in laboratories – at a great expense – thus allowing them to make statements about their products which can be backed up by official government data.

Proper Use:

  1. Read all labels before applying any insecticides or fungicides.
  2. Before spraying insecticides or fungicide make sure the plants are well watered, with more water in the system, plants will suffer less shock from the spray or powder applied to them.
  3. When using contact sprays or powders be sure to follow the cautions set out on the label, i.e. if spraying, be sure to use a face mask or respirator or when applying powders to wear protective clothing and gloves.
  4. Contact sprays and powders must contact the insects in order to be 100% effective.
  5. Do not spray or apply powders in direct sunlight or with HID lamps on. Early morning or evening is preferred/be sure the wind is calm or for indoor environments shut off all circulation fans.
  6. When spraying plants a light mist is all that is necessary. DO NOT WET FOLIAGE – this will damage the plant by burning the leaves, the shock from this will slow plant growth and postpone your harvest date. Be sure to spray stems and surrounding growth medium.
  7. If you see a white residual on foliage from applying contact sprays, you are over applying the insecticide – REMEMBER… A LIGHT MIST IS ALL THAT IS NECESSARY.
  8. Do not spray on vegetables, fruits, vines or herbs with in three days of harvest.
  9. Be sure to spray your plants thoroughly with room temperature Ph balanced water a day before harvest. This will wash off any dust or residuals left on your plants from previous insecticide applications.
  10. If you want your finished product to be 100% Organic, discontinue the use of any synthetic chemicals or any products containing piperonyl butoxide (PBO) as soon as your plants begin to show fruits or flowers.


  1. PYRETHRUM(Tanacetum ‘Chrysanthemuml. Cinrarlifolium) Pyrethrum has been in use since the pyramids in Egypt were built. Pyrethrum is the safest and most effective of all botanical insecticides. A broad spectrum non-systemic botanical insecticide that causes paralysis initially, with death of the insect thereafter. Pyrethrum is very toxic to insects. Applied as a spray, pyrethrum is very effective to control crawling and flying insects. Pyrethrum is non-toxic to animals or humans. Natural pyrethrum degrades quickly in the presence of sunlight or (HID lamps), air and moderate humidity. Pyrethrum is approved for organic gardening.
  2. Insecticidal Soaps are mild contact insecticides made from potassium or sodium salts of fatty acids of animals Soaps are effective in drying up soft-bodied insects only while the soapy liquid is in direct contact with the waxy cuticle of insects such as aphids and whiteflies. Commercial soap formulations are formulated to reduce damage to the plant, but in some cases, plant injury can still occur. Since there is no Insecticidal effect of these soaps once they are dry, growers sometime rinse off the soapy residues. This not only helps the plant, but the rinsing removes additional pests by physically washing them away. None of the soaps are very toxic to animals. Dishwashing soaps and detergents can also be effective against soft bodied insects but have not been formally evaluated as pesticides and may damage the plant by breaking down the waxy layer protecting the leaf surface. Soft soaps such as Ivory are biodegradable and kill insects but are not potent. Do not use detergent soaps, they may be caustic. Soaps take time to mix and must be applied many times to be effective. Soaps do not have any residual effects and are essentially ineffective.
  3. Horticultural Oils are safe, non-poisonous and non-polluting insecticides. Oil kills slow moving and immobile sucking insects by smothering and suffocating them. Oils when applied to plants, clog the stomata and slow the plants growing process. They can control aphids, spider mites, scale plant bugs and lace bugs for up to a week after application. Horticulture oils are typically applied as a 2% solution in water. Although horticultural oils are generally considered safe for use on vegetables, they should still be tested on a small scale to detect possible plant injury on each cultivar prior to large-scale use. Plants in bloom and water stressed plants are most susceptible to oil damage than non-flowering or unstressed plants. Oils and fungicides should not be tank mixed or used within two weeks of each other to avoid toxic effects on the foliage. To avoid ‘boiling’ the plant in oil, horticultural oils should not be used when temperatures are above 90°F. By controlling aphids and thrips, oils have the potential to control virus spread. Oil sprays have been found to slow the spread of virus by delaying primary infection. Once 10% to 20% of the plants are infected, however, oil may not be very effective in controlling further spread. Use horticultural oils with extreme caution as they are not recommended for a large number of plants and ornamentals.
  4. Diatomaceous Earth (DE) is formed by the lacy shells of trillions of minute one celled silicate (algae diatoms) that have died and settled to the bottom of oceans or lake beds. These prehistoric lightweight snowflake-like skeletons have been fossilized. They form deposits hundreds of feet thick that are mined, pulverized and sold as non-toxic wettable powder that is fatal to most soft bodied insects including aphids, slugs and spider mites. Some beneficial insects are also subject to the piercing DE. The diatomaceous earth (DE) works by puncturing or slicing the pest’s body, causing dehydration. If a pest ingests the razor-sharp diatomaceous earth, it disrupts vital body functions. Animals, humans and birds however, can digest diatomaceous earth and are not effected by it. CAUTION: Earthworms, honeybees, caterpillars, predator mites and ladybugs will die if they ingest diatomaceous earth. Use a protective mask when openly handling this fine powder to guard against irritations. Spread DE in a quarter-inch deep, two-inch wide border to prevent slugs and snails from crossing over to eat plants. Mix 1 part DE with 3 to 5 parts water and a few drops of biodegradable dish soap to use as a spray. Apply this spray to infestations of pest insects. A dusting of DE is most effective. Use a commercial duster to apply DE dust to the undersides of moist foliage. The dust sticks to the moist leaves where it stays until washed off by rain, irrigation or manual spraying for indoor environments. For best results, do not water for 48 hours after application. CAUTION! Do not use swimming pool diatomaceous earth. It is chemically treated and heated. This product contains crystalline silica that is hazardous if inhaled. The body is unable to dissolve the crystalline form of silica, which causes chronic irritation.
  5. Rotenone is extracted from the roots of several tropical legumes such as the Cube plant grown in Peru. Originally used as a fish poison by the Indians, it is highly toxic to fish and moderately toxic to humans. A broad-spectrum poison mainly used to control leaf-eating beetles and caterpillars, rotenone breaks down quickly in sunlight or when mixed with soaps or lime. Rotenone is very toxic to humans, be sure to follow precautions as written on label.
  6. Nicotine derived from tobacco, is extremely toxic and fast-acting on mammals. Most organic certification programs do not allow the use of nicotine. The most common use is in greenhouses and to control soft bodied insects such as aphids and mites. Nicotine is only available as a fumigator.
  7. Neem derived from the neem tree of and tropical regions, contains many active compounds that act as feeding deterrents and as growth regulators. The active ingredient is azadirachtin, which is said to be effective on 200 types of insects, mites and nematodes. It has low toxicity to mammals. Three trade names are Margosan-0 (Grace), Einstein Oil and BioNeem (Ringer). Use is restricted to a few states where it has been registered to control white flies, thrips and caterpillars on ornamentals. A neem solution cannot be exposed to direct sunlight (HID lamps) and is effective for only eight hours after preparation. The water used in preparation should be 500 to 950F. It is most effective under humid conditions or when the plants and insects are damp. In Canada, Neem oil is not recognized as a true insecticide as it is unregistered and recommended for ornamentals only. Neem Oil is not a contact spray. It is a systemic – it requires at least 10 days in order for it to be ingested into the vascular structure of the plant, at which time it will prevent the adult insects from multiplying. Unless you maintain absolute sterile conditions, Neem oil will not prevent damage from insects, however it will help reduce the number of insects by preventing the adults to lay eggs. Neem Oil is not approved for food crops. Neem Oil is not recommended in environments with Predator Mites as it will prevent them from laying eggs and will kill them as well.
  8. Sabadilla is an alkaloid derived from the seeds of a tropical American lily. It is most effective against true bugs such as harlequin bugs and squash bugs. Sabadilla degrades quickly. The purified form is highly toxic to mammals. The dust is moderately toxic to mammals, but is highly toxic to honey bees.
  9. Ryania is an alkaloid derived from the stems of a South American shrub. A slow-acting stomach poison with moderate toxicity to mammals, it has longer residual activity than most botanicals. Toxicity to mammals is moderate.
  10. Piperonyl Butoxide (PBO) (synergist) is derived from sesame. Because it enhances the effect of many botanicals, PBO is more appropriately described as a synergist than as an insecticide. PBO inactivates enzymes on the bodies of insects (and mammals) that break down toxins. Using PBO reduces the amount of insecticide needed and increases the likelihood that insects will be killed rather than just temporarily paralyzed. Chronic exposure of humans to PBO can damage the nervous system. Piperonyl butoxide is now made synthetically and is not approved for organic gardening.