©2000 Bonnie Wren
All Rights Reserved

Is There Really an Organic Way to Repel Fire Ants and Other Insect Pests From Our Yards?

The Worm Man

Not long after my fire ant column, "Go Away! Ant That Means YOU" made it into the San Diego Union-Tribune I received a phone call from a reader, a Mr. George Hahn.

After our initial confusion (I thought he was an editor--he thought I was a reporter) Hahn explained that he owns California Vermiculture, the company that produces Wormgold earthworm castings.

My disappointment at not being hired as a columnist was great, but I got over it. Besides, Hahn's subject matter was pretty entertaining.

For those of you who don't know, worm castings are a polite way of saying worm POOP. And Hahn was on the phone to tell me he has the organic solution to California's recent fire ant invasion: worm poop.

The Enzyme

According to Hahn, worm castings contain an enzyme called chitinase. Insects avoid chitinase because it dissolves chitin, the main ingredient in their exoskeletons. If a plant contains a high level of chitinase, Hahn says insect pests like aphids, spider mites and whiteflies shy away from it. He claims they won't walk on it, either.

In other words, when a plant absorbs chitinase with other nutrients from the soil, it makes them taste bad. Insects may take a bite but will say "blech!" and go looking for better tasting chow. If they step on chitinase, they'll cry, "Aieee!" and hurry off to a chintinase-free zone.

To be honest, at first I thought Mr. Hahn was just another overeager salesman and I wished I had thought to pay Pac Bell for an unlisted number. But his enthusiasm was hard to resist and the information he faxed me was interesting.

In addition to general product information about Wormgold (Hahn's brand of castings), he included a copy of a letter written to him by Randall Ismay, Horticultural Consultant for Water and Landscape Consultants of Laguna Niguel.

The Fire Ants

In this letter, Ismay states that he reluctantly yielded to Hahn's prodding and distributed a one-inch thick layer of castings over several dozen confirmed RIFA mounds. To Ismay's astonishment, he observed that, "literally all visible ant activity ceased completely. In every single instance, without even one exception."

Ten weeks after Ismay's initial tests, the fire ants did not reappear in the treated areas.

The Whiteflies

In Hahn's information packet there was also a clipping of a Los Angeles Times article dated Saturday, May 27, 2000 by garden writer Julie Bawden Davis.

Davis wrote that she had been battling whiteflies on her hibiscus plant for over two years without success. But one month after spreading a one-inch layer of worm castings around the base of the hibiscus, she noticed "that the whitefly population had dwindled. Three weeks later there were absolutely no whiteflies on the plant. It's now back to its healthy self and producing lots of blooms."

The Suits

Hahn says he called the California Department of Food and Agriculture to tell them worm castings might be a non-toxic solution to the RIFA dilemma, but was immediately accused of illegally promoting an insect repellent without authorized government approval. They warned him that such claims could result in prison time.

"Heck," Hahn says he told them, "you're going to send me to prison because I tell people to spread worm poop in their back yards? It's already sold everywhere as a fertilizer!"

This is true. Worm castings have long been known to be an excellent organic fertilizer and are sold in countless nurseries all over the world. The stuff doesn't burn and is odor-free, unlike other manure products.

The Professors

Nevertheless, I wanted an expert opinion. I forwarded Hahn's packet of information to the horticultural department at two California universities to ask some experts what they thought about all this.

Dr. Robert Rice from Cal Poly San Luis Obispo was kind enough to send me this response:

I haven't seen any data to support Mr. Hahn's claims in the scientific literature. Mr. Hahn repeatedly refers to scientific evaluation yet does not cite the published sources. . . there are too many variables and the whitefly could have gone away for a completely different reason which coincided roughly with the application of the earthworm castings. So, I am not discounting the possibility that the castings have some repellent properties but until it was evaluated under controlled conditions I am skeptical.

An opinion from another California university was more blunt:

If this stuff really worked we (entomologist, PCA's and people in horticulture) would be recommending the material. Personally, I think he is trying to make money. There is a sucker born every minute! The worm industry was in its heyday a few years ago and people lost money in the "worm business." I believe in biocontrol but it doesn't work in every situation. A lot of claims without any documentation.

Hahn admits he needs scientific research, not just anecdotal evidence to back up his claims. Currently, he says his worm castings are being used in a study at the Quail Botanical Gardens Pinetum in Encinitas, California. And in anticipation of receiving government approval of his worm castings as an insect repellent, he has also applied for a patent.

The Hardhead

Being the hardhead that I am, I decided I'd like to see for myself if this stuff works. While we don't have fire ants in our neighborhood yet, most of San Diego is suffering from an overabundance of Argentine Ants and whiteflies.

I purchased Wormgold worm castings and spread it over an area in my yard where Argentine Ants are a serious problem (I refrained from applying it in my kitchen).

With my neighbor Sophie's permission, I also spread the stuff under her hibiscus plants, which are dying a slow death from whiteflies, as are most hibiscuses in the San Diego area.

I made note of my experiences in a log, but summarized the results of my experiment here.

You might want to experiment in your yard, too. Follow the instructions for using worm castings and let me know what happens. If you give me permission, I'll print your experience on this site.

Remember, Hahn is not claiming worm castings will kill fire ants or other insect pests. Rather, he is saying the castings will repel them.

If it works as Hahn says, when we treat our yards with castings, we should observe insect pests moving to a chitinase-free area, like the neighbors' yards. If so, this might upset the neighbors, but so what? Tell them to get their own worm poop.

The Disclaimer

1. I am not receiving any compensation (not even a free bag of poop!) from George Hahn, California Vermiculture, or any other agency.
2. I am not a gardening expert. I am, however, a mom who prefers to use natural solutions for her insect pest problems. (See "Babies on Board.")
3. You want a truly scientific opinion on this topic, go talk to a scientist.

Subscribe to columns by Bonnie Wren and earn her undying gratitude.

The Results