Soil Fumigating Guide – When Should You Fumigate Soil

Soil Fumigating Guide – When Should You Fumigate Soil

By: Teo Spengler

What is soil fumigation? It’s the process of putting pesticides known as soil fumigants on the soil. These pesticides form a gas that is supposed to deal with pests in the soil, but they can also injure people applying them and others nearby. Should you fumigate soil? For more information on soil fumigating, plus tips on how to fumigate soil, read on.

What is Soil Fumigation?

Fumigating soil means applying a special type of pesticide that turns into a gas. The gas passes through the soil and controls pests that live there, including nematodes, fungi, bacteria, insects and weeds.

Should You Fumigate Soil?

The pesticides you use when you are fumigating soil turn into gas once you apply them. The gases pass into the air above the area where they were applied. They can also be pushed by the wind to other nearby areas. When the gases come in contact with people, like agricultural workers, they can produce serious negative health effects, some temporary, some irreversible. This can happen hours or days after they were first applied.

In addition, the process is not always successful. Unless a grower takes great care, it’s very possible to re-infest a recently fumigated area with pathogens. One common way this happens is by moving equipment from infested fields into fields already treated. This raises the obvious question: should you fumigate soil?

Since fumigation is also very expensive, growers must carefully weigh the anticipated benefits against the actual costs and potential health risks.

How to Fumigate Soil

If you are wondering how to fumigate soil, it is a very complex process. Fumigants are safe and effective when they are properly used by trained individuals, but absent special training, they can be dangerous.

In many areas, only licensed individuals can legally do soil fumigating. It may be wise to bring in an expert for soil fumigating since a host of factors can affect the movement and effectiveness of fumigants. These include the type of soil, its temperature, moisture levels and organic matter content.

It is also important to prepare the soil properly before doing soil fumigating. You also must select the type of fumigant that will best serve your needs and determine how deep to apply it. This also varies according to dosage, soil features and pests to be controlled.

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How to Get Rid of Fungus in Garden Soil

Of all the problems that plague a garden, soil-borne pathogens are the worst. Here’s what to do when a fungus wrecks your plants.

Fungal Leaf Spot

Leaf spots originate with bacteria or fungus, both of which reside in soil or on nearby plants. Read on to find out what to do when a fungus takes over your garden.

Photo by: Julie Martens Forney

Leaf spots originate with bacteria or fungus, both of which reside in soil or on nearby plants. Read on to find out what to do when a fungus takes over your garden.

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Gah! Your garden has a fungus. Some microscopic, plant-killing pathogen has infected the soil, and now your tomatoes are stunted and yellowing, your onions are rotting at the ground and your pepper plants are laying on the ground with black spots on their dying leaves. So much for that garden-fresh salsa.

Soil-borne diseases like fungus are one of the most frustrating things a gardener can deal with because you don’t know it’s there until it makes your plant sick. And once you realize there’s fungus in your soil, it’s not easy to get rid of it. Soil-born diseases can live in your soil for a long time, waiting for you to put a plant in the ground. Once you do, the pathogen hops aboard that hapless host plant and spreads through your garden like wildfire.

Soil Preparation

As with all soil fumigation, the first step is to properly prepare and till the soil. Current soil preparation and bed listing practices used after methyl bromide fumigation are generally adequate. Following this, firmly pack the beds and eliminate any dirt clods. If the soil is dry, it may be necessary to preirrigate with enough water to initiate weed seed germination (1–1.5 acre-inch).

Uniform water distribution is necessary in a drip irrigation system and is easiest to obtain on fairly level terrain. On steep or hilly fields, create beds that follow soil contour lines at grades that do not exceed 4 feet uphill or 8 feet downhill from the beginning of the drip line.

When laying the plastic tarp, remove any shanks or chisels to avoid creating channels in the soil, which can result in poor water and fumigant distribution in the soil bed. Repair any holes or tears in the plastic tarp. Avoid embossed tarps to reduce loss of fumigants through volatilization. The use of totally impermeable film (TIF) will enhance weed control in the bed. However, TIF holds fumigants in the soil for longer periods than the standard tarp, so a longer plantback time or bed ventilation for 2 weeks before planting may be required (refer to the pesticide label).

Related Discussions

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I would be afraid of harming the soil with bleach solution. Even though I am not an organic gardening zealot, I believe micro-organisms are necessary for a "healthy" soil. There is no question that bleach will kill most micro-organisms, both good and bad.


I wouldn't use bleach, I'd drench the soil with 20% vinegar.


We had a swimming pool that was treated with chlorine, and it drained into a flower/shrub bed and onto the lawn. The plants and the grass were in excellent health for all the years we were there, so I can't see that it would hurt anything if properly diluted. Just my opinion, not based on science.

Here is a link that might be useful: Annie's Kitchen Garden


Bleach decomposes instantly when it comes in contact with soil organic matter. It won't work don't waste your money. On my farm I used to use fumigants, they will kill disease in the soil but only temporally. Nature hates a vacuum and the diseases return. If you can rotate your garden to a new spot every three years that will solve most of the problems. Bob.


I like the idea of controled burning at the end of the garden season .Bleach and hydrogen peroxide do return to original state (harmless water)within several hours. I have poured bleach on weeds against the house and nothing seemed to ever grow there again .

-researchers found that injecting salt water with electrical current broke down the salt (sodium chloride) molecules and produced a compound called sodium hypochlorite. This discovery enabled the mass production of sodium hypochlorite, or chlorine, bleach.


Thanks to all who have responded to my question. I'm impressed with all the answers given. Maybe my friend isn't crazy after all. I would never have thought of controling diseases in the soil this way, but if that is what she wants to do I guess that is up to her. I will give her some of your suggestions, maybe she'll use one of them instead of the bleach. Thanks to all who have responded, I really appreciate your help and insite. Lisa


I am very interested in sterilizing the soil in my vegetable garden. I had trouble with fusarium wilt killing three of my tomatoes--Amelia, Cupid, and--though it took a long time--Heat Wave.

I have a Better Boy growing next to the Amelia and it was never affected at all. And both, according to Park's Seed Catalog, are resistant only to race 1 of fusarium wilt. So why was my Better Boy spared? They were less than 3 feet apart.

I wonder if watering the garden with hydrogen peroxide with one of those hose sprayers would kill the fungus? It seems to me, it wouldn't go deep enough into the soil.

What about Vapam? It is a soil fumigant. I used it once, over 20 years ago, and it really worked and the garden could be planted a month after application. But it sounds pretty poisonous and I don't even know where to get it. I haven't seen it in years.

My garden is 12' by 12' and so I can't rotate it. I can put the tomatoes in another part of the garden, but it does get some shade and I had to put the tomatoes where they would get the most sun. I also grew cucumbers and green beans, which all did quite well.


I'd be more apt to examine the gardening practises before I'd start dumping gallons of bleach on the ground. A better use for the bleach would be to disinfect all your stakes, cages and garden tools that you're using. Use mulch on the ground to keep the early blight contained on the ground instead of splashing up on the plants. For the fusarium wilt, try Mycostop, it's an approved organic spray.

Seeds can also come contaminated too, so maybe that is a source?

I think if you're interested in "sanitizing" your soil, using a propane weed torch to systemically burn the garden would be a better way to do it, and probably would result in better sanitizing than bleach solutions would. I don't understand the point of growing your own if you're going to dump bleach in the ground, your soil is the most crucial part of your garden and temporarily sanitizing things won't stop re-infection from occurring if it's source is cultural practices in your garden.

Weeding is crucial in controlling plant diseases as well, various weeds are hosts for all sorts of things.

When I sterilize my carboys prior to brewing beer, I place a couple tbsp bleach and a gallon of water in each carboy, swish it up and down the carboy, and dump it on my patio. As the solution trickles over the edge of the patio and into the lawn, earthworms come out writhing like mad, clearly in extreme distress. And it is a fairly dilute solution. I have no doubt that bleach will kill the entire garden micro-fauna.

I would not consider growing tomatoes without mulching them thickly with wood chips. It saves water, weeding, and minimizes early blight. Crop rotation should do the rest, though I understand that in small gardens it is not always possible. There is also a broad spectrum of resistance to early blight. In my experience, Yellow Pear, Stupice and Early Girl do very well, Brandywine and san Marzano a bit less so, but they still produce, and Costoluto and Jubilee (an orange tomato) do very poorly.


I'd be very leery of trying to sterilize your garden with bleach. To get the diseases you are after, you would probably have to thoroughly soak the soil. When the bleach goes into the soil, it begins degrading the organic matter that it contacts, all the humus, all the micro-organisms, etc, so I would expect it would take quite a large quantity to remove all the disease organisms to whatever depth they go down to--maybe a foot.

Doing this would have a couple negative effects--first, the sodium hypochlorite will break down into salt and with large quantities you will be salting out your soil and damaging its structure. At some point, the salt will have to be eliminated or little may grow. Secondly, removing the pathogens will also remove many of the billions of good bugs in the soil and reduce its health in other ways. Might as well bake the soil in the oven. It will sterilize it just as well or better, but won't destroy all the organic matter and won't salt the ground out.

Much better to go after it in other ways. Eliminate any diseased foliage from the garden immediately. Remove all host plants at the end of the season to reduce the residue for the pathogens to survive on. Use mulches to prevent rain splash from infecting leaves. Plant resistant varieties. Look for other controls, "organic", chemical, or other. Move your susceptible plants to different locations in the garden each year, or move susceptible plants and hosts out of the garden for several years (hide the tomatoes here and there in the flower beds).

Several years ago I noticed increasing problems with blight in tomatoes. At the time, I was adding large quantities of well rotted manure to the soil. Decided that the manure might be helping to host the blight in the soil or at least giving it a favorable environment, so backed off considerably in how much I apply. The blight problems dropped off considerably.

Soil Fungicides

Fungal diseases can be some of the most damaging and costly conditions for organic growers to combat in the garden. Even if you are not seeing extensive damage, the pathogens may be thriving underground while sapping vital energy from the plants and reducing harvest yields. Soil fungicides are anti-fungal products that prevent and kill fungal diseases growing in the soil medium. Best used preventatively, soil fungicides come in a variety of forms from pH buffers to biofungicides.

Biofungicides are in increasingly high demand due to their complementary activity with other microbial life in the soil. Most biofungicides allow beneficial fungi, bacteria and other plant-symbiotic organisms to thrive while targeting and outcompeting the detrimental ones. Common ingredients in biofungicides include:

  • Trichoderma harzianum
  • Bacillus subtilis
  • Streptomyces lydicus
Whether you are a gardener or farmer, always identify the disease being treated if symptoms are present. Either consult with a local farm extension agent or call us at 1-800-827-2847. Once identified, it is time to select the best organic fungicide for the job.

Browse ARBICO's selection of organic fungicides below!

Watch the video: How to Sterilize Soil in the Garden: Grow Guru