Any number of insect pests can invade your garden, and many gardeners come to rely on chemical pesticides as their first line of defense against crop damage. One of those reliable foot soldiers in the pest war is carbaryl, sold under the Sevin brand name and others. It's effective against dozens of insect pests that would otherwise attack your tomatoes and other vegetables, but if you use Sevin dust on tomato plants, it must be used with care to avoid collateral damage to the gardener, children, pets and the environment.
What Is Sevin Dust?
Sevin is a well-known brand name for the chemical carbaryl. It's a toxin that attacks the nervous system of insects, killing them within minutes of exposure. It's available in other forms, including spray and granules, but Sevin dust is popular because it's easy and uncomplicated for amateurs to apply.
Once the pesticide is in place on your tomato plants, it provides protection from a wide range of insect pests for up to three months. As a dry powder, it can be washed off, though, so if you live in an area that's prone to heavy rain, you'll probably need to reapply it once your plants have dried. Also, you should irrigate your tomatoes with drip hoses or water them at the base of the plants rather than using a sprinkler or simply hosing them.
Using Sevin Dust on Tomatoes
Before you apply Sevin dust or any other powerful pesticide, read the label carefully and be sure you understand and follow the manufacturer's guidelines for safe application. At a minimum, you'll need to wear eye protection, long sleeves and pants and chemical-proof nitrile gloves for your hands.
Choose a dry day with minimal wind, ideally at least 24 to 48 hours after the last rain but as soon as possible after you notice the first sign of insect activity or damage. To apply, simply sprinkle a light, even dusting of Sevin over the entire tomato plant right from the canister's built-in shaker. It's like dusting a cake with icing sugar; you'll easily be able to see the dust on the plant's leaves and fruit. Start at the back corner of your tomato bed and work your way to the front so you're not walking through the already-applied area or accidentally applying the pesticide twice.
The dust needs to settle completely before you resume normal gardening activities, so give it at least a few hours — or ideally, the remainder of the day — before you go back into the garden in short sleeves.
Sevin Dust Pre-Harvest Interval
An important statistic with any pesticide is its pre-harvest interval, or PHI. This is simply how soon after you've applied a pesticide that it's safe to harvest and eat the fruit or vegetable in question. In the case of Sevin dust and tomatoes, the company's PHI chart suggests that one day is a safe interval for tomatoes. You can use Sevin dust one day and harvest ripe tomatoes the next. PestGuide.org recommends soaking your vegetables after harvest and then thoroughly rinsing them to remove any residue left from the Sevin dust.
Risks of Sevin Dust
It's important to adhere to recommended safety measures when using Sevin because like most similar pesticides it is — to be blunt — thoroughly nasty stuff. The company's own safety data sheet for the product details the potential result of accidental inhalation or exposure: blurred vision, a drop in blood pressure, nausea and vomiting, diarrhea, difficulty breathing and potentially coma or death. It's also a recognized carcinogen.
Because of their smaller body weights and their inability to read and follow safety instructions, Sevin is highly dangerous to small children and pets. Furthermore, it can lethally impact beneficial insects (both pollinators and predators) and insect predators such as birds. Ironically, this can mean you'll sometimes face worse insect problems. Purdue University warns that insects that aren't affected by carbaryl, such as aphids and spider mites, will flourish once you've eliminated their rivals and predators.
Alternative Pest Control Measures
This indiscriminate toxicity makes broad-spectrum pesticides like Sevin the home gardener's "nuclear option," and it's worth considering less toxic options first. A good starting point is to simply follow good cultural practices:
- Choose tomato cultivars that are well-suited to your area and climate and buy certified disease-free transplants and seed from reputable sources.
- Keep weeds controlled and space, feed and water your plants as recommended. Healthy, vigorous plants are less susceptible to pests and disease.
- Use row covers when your tomatoes are small, which can prevent many pests from getting established or laying eggs.
- Use companion planting to discourage pests.
- Rotate your crops regularly. Don't plant tomatoes or close relatives, such as eggplant, peppers or potatoes, in the same place year after year. This encourages pests to accumulate.
Inspect your plants regularly so you can detect the earliest signs of insect damage before the pests get established. Depending on the pest, simply picking them off by hand may nip an infestation in the bud. Many pests can also be controlled by less harsh pesticides, including neem oil, pyrethrum or Bacillus thuringiensis (Bt). Finally, you may opt to simply exercise a little forbearance. Most gardeners struggle to keep up with the peak-season glut of tomatoes as it is. What's the harm, really, in allowing caterpillars to eat a few?
Fred Decker is a trained chef and prolific freelance writer. He was educated at Memorial University of Newfoundland and the Northern Alberta Institute of Technology. His articles have appeared on numerous home and garden sites, including OurEverydayLife, GoneOutdoots, The Nest and eHow, as well as the San Francisco Chronicle's SFGate.com.