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The best caterpillar control

If you're watching your veggie garden being digested by caterpillars, fight back with a natural product that stops only them.


© St. Petersburg Times, published April 28, 2001

Spring is caterpillar time in central Florida. Maybe your yard looks like a scene from that '60s Japanese sci-fi movie Mothra, with giant caterpillars wreaking havoc before transforming into winged beauties. Sod webworms may ravage your St. Augustine lawn, and cabbage looper caterpillars may strip your mustard and broccoli bare. You may even have found a tomato hornworm so big you couldn't stand to pick it off and step on it. I've seen oleanders looking furry with orange caterpillars that have long black hairs.

Before we declare war on them with insecticides, even natural ones, let's remember that those crawling, munching monsters mature into butterflies and moths, many cherished for their beauty and grace.

Let's control them only where they can render harm, in the veggie garden and St. Augustine lawn. Let's also feed our favorites by planting butterfly weed, flat-leaf parsley, fennel and dill in our flower gardens for the baby caterpillars to feed on.

Organic gardeners enjoy a help from natural allies such as birds and wasps that eat caterpillars and carry them off to their nests for their young to feed on. I have even seen wasps clutching caterpillars in their legs while in flight.

Since we don't want our food crops and lawns ruined, we need a specific tool to quickly destroy caterpillars where they are not wanted. Luckily, this silver bullet has been around since the 1930s and is available in many garden shops and feed stores.

It's a natural bacteria called Bacillus thuringiensis (BT), sold under product names such as Dipel, Biotrol and Thuricide. This plague of the caterpillar world is not genetically engineered and doesn't hurt any other living things; not honeybees, earthworms, butterflies, kids, pets, birds or in-laws.

Caterpillars ingest it by biting a leaf sprinkled with BT. The organisms multiply inside their bodies, paralyzing their digestive tracts with sharp crystals of a protein that is toxic to them. As a result they quit feeding on your plants, often within 20 minutes of that first bite. Soon, they die, and their bodies split open, releasing billions more bacteria to further protect your lawn or garden.

That is why BT is the kiss of death for the butterfly garden so many of us have enjoyed creating and living with. Use it judiciously, and only where needed. My experience in 20 years of gardening in the Tampa Bay area is that just one application permanently inoculates the organically maintained lawn or veggie garden; the bacteria are soil dwelling and welcome the absence of fungicides and agricultural antibiotics. To be sure you have enough of them living in your lawn or garden, consider reapplying BT each spring. It is least expensive in 3-pound bags from feed stores and is available in 1-pound canisters at many garden shops.

I never use the liquid forms, as the petroleum distillates they contain force the bacteria into the spore stage, delaying their becoming active in the garden. Just sprinkle the powder on the damp leaves or lawn so the moisture can bring the bacteria to life. Some folks prefer to mix the powder into bottled water (the chlorine in tap water can kill the bacteria) in their garden sprayer, then spray it just where it is needed.

None of us want caterpillars pillaging our yards, but butterflies and moths are essential aspects of the color and charm of Florida. As more of us invite them in with butterfly gardens, perhaps fewer will become extinct as a result of habitat loss.

But caterpillars on my broccoli? Ear worms in my corn? No thanks!

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John A. Starnes Jr. is an avid gardener and rosarian who studies, collects, cultivates and hybridizes roses for the diverse regions of Florida and Colorado. He can be reached at:

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