San Antonio Express News
GARDENING, Etc.
Sunday, June 13, 2004

By Nathan Riggs

These days, many gardeners and outdoor plant enthusiasts are seeking to use more “natural” products to control pests in their landscapes. While there are not too many “natural” options available, the ones on the market can provide some relief in the bug and weed battle. For clarification, the use of “natural” or “organic” in this article refers to ingredients that come from a natural source. For all of you familiar with Extension, you know that we can only suggest methods that are backed by legitimate research efforts. Some of the ingredients below come from anecdotal evidence and do not have research proof as of yet. Let’s look:

• NEEM
  Extract of the Neem Tree seeds (contains azidirachtin).
  Has fungicidal, insecticidal and insect anti-feeding properties.
  Kills aphids, scales, mealybugs, thrips.
  Use in gardens, lawns, landscapes
• PYRETHINS
  Extract of the African Chrysanthemum Daisy.
  Powerful, natural insecticide that is sensitive to UV rays from the sun.
  Kills all insects on contact with two or three day’s residual activity.
  Use in gardens, lawns, landscapes.
• SPINOSAD
  Extract of a fermentation process of a soil bacteria.
  Kills caterpillars, borers, leaf-feeding beetles, leafminers and fire ants; sensitive to UV rays.
  Gentle on beneficial insects like lacewings, wasps and ladybugs.
  Use in gardens, lawns and landscapes.
• DIATOMACEOUS EARTH (DE)
  Made from the skeletons of microscopic diatoms (sea creatures).
  Skeletons are made of glass (silicon dioxide).
  Processed DE is crushed into a powder with jagged edges.
  Affects insects by abrading (scratching) their exoskeletons, making them susceptible to desiccation (drying out).
  Use outdoors in any situation.
• ORANGE OIL (d-limonene)
  Extracted in a cold press process from citrus peels.
  Affects a wide variety of insects.
  Can cause damage to plants or grasses if applied too strongly.
  Apply to lawns, gardens and landscapes.
• ROTENONE
  Extracted from roots of seven genera of tropical plants.
  Kills a wide variety of insects. Also very deadly to aquatic organisms, including fish.
  Apply to gardens and ornamentals.
• KAOLIN CLAY
  A powdered, processed form of clay used in horticulture that is sprayed onto plants to deter insects from feeding.
  The spray leaves a harmless, white film on the leaves that does not affect photosynthesis, but protects against sunburn and heat stress.
  Sold as Surround® WP Crop Protectant.
• BACILLUS THURINGIENSIS
  Toxic crystals formed from stressing Bt bacteria.
  Crystals are toxic only to caterpillars and mosquito larvae when eaten.
  Comes in dusts, liquids and bait granules.
  Apply to gardens, ornamentals, landscapes or standing water.
• INSECTICIDAL SOAP
  Not a true soap; it is a fatty acid preparation of a salt.
  Kills soft-bodied insects (aphids, scales, mealybugs) on contact; residues are not effective.
  Apply to gardens, lawns, ornamentals, landscapes.
• HORTICULTURAL OILS
  Light paraffinic oils
  Sprayed onto trees in winter or some plants in spring or summer.
  Covers and suffocates insect eggs as well as aphids, scales and mealybugs.
  Time of year is very important when applying; can cause plant damage. Don’t spray during the heat of day.
• AROMATIC PLANT OILS*
  (Clove Oil, Thyme Oil, Rosemary Oil, Wintergreen Oil)
  Extracted from various plants and emulsified to mix effectively with water.
  Very effective at repelling insects; may kill some on contact.
  Apply to gardens, lawns, landscapes.
  *Not widely tested at the university level.
• CEDAR OIL
  Extracted from cedar trees.
  Very repellant to all insects.
  Apply to lawns, landscapes and gardens.
• BENEFICIAL NEMATODES
  Microscopic soil-dwelling worms that attack insects under the soil.
  Will attack and kill flea larvae, white grubs, mole crickets, fungus gnat larvae, termites and other soil insects underground.
  Require moist soil to survive.
  Will not harm animals or plants.
• NOSEMA LOCUSTAE BAITS
  Contains infective spores of the protozoan Nosema locustae.
  Effective at killing young grasshoppers up to 3rd instar stage.
  Apply early in the season when small grasshoppers are present.
  Apply to lawns, landscapes, pastures and gardens.
  Harmless to people, animals and other insects.
  Sold as Nolo-Bait® and Semaspore® Bait
• VINEGAR*
  Used as an herbicide, but provides top-kill only of sprayed plants; non-selective.
  *Not tested at university level
• LIQUID SEAWEED*
  Used as a foliar nutrient for plants.
  Master Gardeners have noticed that whitefly and spider mite populations decrease on plants sprayed with liquid seaweed.
  *Not tested at the university level

As you can see, there are natural products on the market that have the ability to provide some help against pests in the garden or landscape. Even though these ingredients come from natural sources, some of them are still very powerful (pyrethrins) in their own right and must be used with caution, and exactly as the packaging directs. As more research is done on these ingredients, perhaps more “organic” products will enter the market place.

Nathan Riggs is Extension Agent-IPM with Texas Cooperative Extension in Bexar County. For more information, please call 210 / 467-6575.