A Chemical-Free Answer to a Bug-Free Garden
4/10/01

By Russell Enos
Commercial Sales Associate, Miramar Wholesale Nurseries

Don’t like to apply chemical pesticides to your plants? Wormcastings could be nature’s alternative to costly and sometimes useless insecticides and fungicides. Wormcastings are a non-toxic, easy-to-use method of repelling insects on ornamentals.

If you’ve ever lifted or moved a potted plant and found granules of soil pellets in small piles at the drainage holes, then you’ve seen evidence of earthworms at work. As they burrow, they help aerate the soil while breaking down organic matter into simpler forms that are more readily absorbed by plants. This process occurs in the worm’s digestive tract, and the waste material is called “wormcastings.”

Research shows that wormcastings stimulate micro-organisms in plants that produce an enzyme called chitinase. Chitinase dissolves chitin, and it is chitin which makes up the exoskeleton of an insect. Wormcastings do not actually kill insects. They simply activate the plant’s natural insect repellant so bugs no longer find the plant desirable.

Research to genetically alter plants to produce high levels of chitinase is underway. However, wormcastings are available now. They are 100% organic, non-toxic, plus they eliminate pathogens and contain no salts — so will not burn. Also, wormcastings can be used without fungicides, insecticides or other poisons. It takes about 25% more wormcastings annually to be effective when not paired with these traditional methods of repelling bugs.

Aphids, whitefly, spider mites, some scale and other bugs that feed on plant juices are susceptible to wormcastings. Tests also show wormcastings are effective in controlling some fungus problems by releasing nitrogen, which also helps plants grow.

APPLICATION
Wormcastings are effective, but they don’t work overnight. The chitinase-producing organisms in the plant have to multiply to levels high enough for the pest to detect, then the pest will go away. A small houseplant with spider mites will become repellant in about two or three weeks. Roses will repel aphids in about two months, and a 10-foot hibiscus with whitefly may take up to three months to begin repelling its pests.

Tests show that using a 10 percent to 20 percent (a one-half- to one-inch layer) ratio is most effective.

OUTDOOR PLANTS
To prepare existing outdoor plants, begin by raking the top of the soil, but be mindful of surface feeder roots. Add a one-inch layer of castings from the base of the plant (about one-inch out) covering from root pattern to drip line. Cover with a one-inch layer of compost. Water.

Note: Worms cover each casting with a mucous coating which makes each casting repel water, unless it is allowed time to soak. The layer of compost will hold the moisture and allow water to soak the castings.

POTTED PLANTS
Scratch the top of the soil of your potted indoor or outdoor plants to one-half inch. Add a one-half- to one-inch layer of castings, followed by a layer of compost. Water.

NEW PLANTINGS
Mix a 10 percent ratio with any potting soil or planters mix. Place a one-half-inch layer at the base — castings are needed where the roots will be located. Plant and water.

To keep your plants chemical free and pest free, an additional 25 percent of the original application is needed annually. Wormcastings can be found at your local commercial landscape center.

Russell Enos is a Commercial Sales Associate at Miramar Wholesale Nurseries, Southern California’s leading supplier of landscape plant materials and supplies. The nurseries carry bagged “Wormgold Castings” in 20-quart containers.