Nematodes Versus Ants Review: So-so Results


Photo: Premier Tech Home & Garden

I recently tried using beneficial nematodes to control ants in my yard. Not that I really had to: I’m pretty open to ants as long as 1) they stay outdoors and 2) don’t attack people. But I had recently taped a TV show about using nematodes to control insect pests and ended up bringing home a sample of AntOut Nematodes. Since I had the product, I figured I’d try it and write about the results.

The product in question comes in a round plastic ball and does not require refrigeration. (This is fairly new; previous generations of nematode treatments required refrigeration both in the store and at home.) It does have a limited life span, though, and has been to used the year in which it was purchased. 

Background Story

Steinernema feltiae as seen under a microscope. Photo:

Nematodes are microscopic worms. There are thousands of species, some of which are harmful to plants, but many others are parasites of insects. That’s the case of Steinernema feltiae, the species of nematode used in the Green Earth product. Besides ants, this species can treat other pests such as flea beetles, houseflies, sawflies and fungus gnats. Other nematode species and strains are available that control white grubs, chinch bugs, fleas and other pests.

Two Test Colonies

Meadow ants build tiny mounds and aren’t really worth treating. Photo: University of Nebraska Extension

I have dozens of colonies of meadow ants (Lasius spp.), little brown ants that make small crater-shaped mounds of soil particles with an entrance hole in the center. They’re found in my lawn, gardens and among paving stones. They’re essentially beneficial: they aerate the soil, pick up detritus and do no harm to my plants. I’ve never bothered trying to eliminate them, nor do I intend to: live and let live, I say. I’m assuming most other gardeners feel the same way.

Field ant nests are larger, have multiple entrances and tend to kill the surrounding vegetation. Photo:

However, there were two colonies of field ants (Formica spp.) in my yard. These are larger ants, usually black (mine were), although they do come in other colors, and they build bigger sandy-looking nests with multiple entrances. They’re not carpenter ants (they live in wood) and almost never go indoors, but their large nests often destroy plantings and sections of lawn, mostly through burying plants and excessive tunneling. They’ll even bite if you attack their nests, but their bite is more surprising than painful. And field ant colonies are long-lived: up to 10 years. 

Given their more harmful nature, I decided field ants would be the ones I would treat.

Field ant (Formica spp.). Photo: Mathias Krumbholz, Wikipedia Commons

One colony was in my lawn and had been there for a number of years. Not being a lawn person, I had simply been ignoring it. My belief was that this colony was in decline: it didn’t seem that vigorous. I’ll call it the lawn colony.

The other was a new one, first seen this spring, and it was coming up near my front door, half in paving stones and half in a flower bed. Their mound was growing weekly. I’ll call them the paving stone colony.

The Treatment

I first read the label on the product and it suggested spraying them onto nests. However, on the Web site I found instructions for watering them in … much more practical for me.

The tiny filter bag containers filler, but also invisible-to-the-eye nematodes. Photo:

It certainly was simple enough. I was to soak the area the previous day (done), then open the ball and remove the tiny filter bag of filler that container the dormant nematodes. As instructed, I dropped the bag into a 5-gallon watering can and filled it with water. 

The nematode solution has to be watering in or sprayed on.

Apparently, the product can cover 16 ant nests or up to 3000 sq. ft (275 m2), but I had only two nests. So, I slowly poured about one quarter of the solution onto and around the lawn colony, then did the same for the patio one. After, I repeated simply because I had enough product to do so. Then I was to water the product in, which I did.

Follow-up was to consist of watering daily for four days. I did that too.

The Results

There is nothing left of the lawn colony and grass and other lawn plants are filling back in. Photo:

By day 4, the lawn colony was gone. Not a living ant has appeared since and the lawn is actually filling in already. But the patio colony showed no reaction at all and continues to prosper.

My thoughts: the lawn colony might have been especially susceptible to the nematodes, since it seemed already to be on the decline, while the patio colony, being young, might have been more vigorous and resistant. Or perhaps the main nest was out of reach of the nematodes, situated as it was under patio pavers. 

At any rate, the nematodes are supposed to multiply and remain alive for the season, so they might yet seek out and destroy the patio ant colony. And I would think conditions are good for them right now, as it has been rainy ever since I applied the nematodes. However, they’re not tolerant of prolonged periods below freezing and will likely be killed in the cold winters where I live. So, if the colony does not reappear next spring, that could still be the results of this summer’s treatment. If so, I’ll update this article. 

However, at this point, treating ants with nematodes doesn’t seem to be a miracle solution, working in some cases, but not in others.

At least you’re now forewarned!

Using Beneficial Nematodes Against White Grubs



White grubs at three different stages. Photo: David Cappaert, Michigan State University, Wikimedia Commons

You can treat infestations of white grubs (larvae of June beetles, European chafers, Japanese beetles, rose chafers, etc.) in the lawn with nematodes, small parasitic worms that infect and kill young larvae. There are various species of nematodes that will do the job, mostly in the genera Steinernema and Heterorhabditis. They work by penetrating their host and injecting bacteria that kill them.

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Nematodes are parasitic worms too small to be seen by the naked eye. Photo: CSIRO

Note that beneficial nematodes are harmless to beneficial insects, such as bees and ladybugs, as well as earthworms, and also to birds, reptiles, amphibians, mammals, etc., although they also help control other harmful soil insects such as weevils, fleas, borers, wireworms, onion maggots and fungus gnats.

In the Northern Hemisphere, nematodes are best applied at sunset or on a cloudy day between mid-August and early October in cooler climates, mid-July through August in mild ones, as that is when the grubs are freshly hatched and most vulnerable to infestation. The soil should be warm (70 to 86˚F/21 to 30˚C) and moist (apply after rain if possible, otherwise water deeply the day before).


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Some brands of nematodes can be stored at room temperatures.

You should be able to find beneficial nematodes in your local garden center. If not there are many mail order sources on the Internet. In years past, you had to ask for them, as they were stored out of sight in a refrigerator (likewise, they have to be stored in a refrigerator at home until you’re ready to use them). However, recent technological developments in storage methods have led to some brands that don’t require refrigeration, although they must not be stored in sunlight.

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Nematodes can be applied using a hose-end sprayer. Photo: Spray-N-Grow

To apply, mix the product in water and spray on the lawn, following the instructions on the product purchased (they’ll vary a bit depending on the species of nematode and the way the supplier has packaged them). Water the lawn after the application and as needed over the next 14 days so the soil remains moist, especially in heavy or clay soils, as this ensures that the nematodes will descend deep enough into the soil to reach their prey.

Combined with other control methods (such as turf enriched with compost, mowed high, and mixed with other plants such as clover), you’ll find nematodes quite effective… in the medium and long term. But not necessarily the following year! That’s because nematodes are especially efficient in killing freshly hatched white grubs in the first year of their cycle, the ones that hatch in July (mild climates) or August (cool climates). They’re not so good at controlling 2nd-year grubs (those that live two years underground, as is the case with June beetles), the ones that will cause the most damage the following year. That’s why it is often in the third summer you’ll see the full results of your treatment, because that year’s generation will have been largely eliminated. Once introduced, beneficial nematodes can remain in the soil for many years, providing long-term control.

Note that it is not necessary to eliminate all the white grubs from a lawn to get excellent results. A healthy lawn can tolerate a modest population of white grubs without showing the typical symptoms (brown patches in the lawn). That’s what you should strive for: a natural balance in your lawn’s environment, one that will give you a healthy lawn without disrupting Mother Nature’s cycle.20170828C CSIRO

Choose a Pesticide With the Narrowest Possible Spectrum



Most pesticides sold in garden centers have a broad spectrum: they indiscriminately kill anything within their range.

The ideal pesticide would be the one with an extremely narrow spectrum, acting on only one enemy and nothing else. Thus, the impact on the environment would be minimal: a single insect, disease or plant would be eliminated without negatively affecting anything nearby.

Right now, though, most pesticides on the market are quite the opposite: they are broad spectrum products. This includes insecticides that kill all insects, even ladybugs and bees; herbicides that eliminate all broadleaved plants including the lilies and foxgloves in your flowerbed; and fungicides that attack pretty much any fungus, even the ones needed to decompose plant debris and dead leaves.


Btk is a bacteria that only kills caterpillars.

However, there have been some interesting breakthroughs into more specific compounds that affect only a limited range of pests. Think of the highly popular Btk (Bacillus thurigiensis kurstaki), which only kills caterpillars (moth and butterfly larvae) and nothing else, and of beneficial nematodes (Steinernema, Heterorhabditis and others) that only infect grubs, maggots and other insect larvae that chew on plant roots underground.

A lot of very promising research is being carried out in this area. One day, we’ll probably be able to obtain an organic pesticide that only acts on goutweed (Aegopodium podagraria) or red spider mites and absolutely nothing else. That will certainly make gardening easier while reducing any negative environmental effects.

In the meantime, however, apply any pesticide, even an organic one, with precaution, as there is always risk of collateral damage.20170207a

Controlling Those #$@&%* Japanese Beetles



Japanese beetle (Popillia japonica)

No, they are not easy to control! Japanese beetles (Popillia japonica) have been the scourge of the North American garden world ever since they were accidentally introduced to New Jersey in 1916 (happy 100th, Japanese beetle!) and have been spreading steadily ever since. They are established throughout much of Eastern North America and are now found in all states east of the Mississippi. In Canada, they got to Nova Scotia rather early, but only recently moved into Quebec, Ontario and New Brunswick in a big way. Even so, they tend to be very localized: you may well have a major problem with this insect in your town while nobody in the neighboring village has ever even seen one.

The Japanese beetle also moved into Italy in recent years and it is feared that it will spread throughout Europe over time.

Bad Eating Habits


Japanese beetles will skeletonize leaves.

Japanese beetles have been discovered eating over 400 different species of plants, from perennials, annuals and vines to trees and shrubs (but rarely conifers). The adult beetles chow down on leaves, flowers, and fruits. They often skeletonize leaves, often leaving only the veins, then the leaves turn brown and fall off. From a distance, a severely affected tree may look like was scorched by fire. After the beetles stop feeding, the affected plants usually produce new leaves and therefore don’t suffer as much from the infestation as do their human owners, but several years of defoliation can certainly weaken a plant or even kill it.

Japanese Beetle Host Plants

Here’s a link to a list of over one hundred of the Japanese beetles’ favorite food plants.

At Closer Look at Japanese Beetles


Really rather handsome, don’t you think?

The adult is a plump beetle about ½ inch (13 mm) in length with a metallic green head and body and copper brown wing covers. They also sport six rather spiffy tufts of white hair along each side of wing covers. All in all, it’s a mighty handsome beetle… if you’re into beetles, that is.


Various stages of Japanese beetle grubs.

The larva is a white grub that lives underground. It’s one of the famous white grubs, the larvae of May/June beetles and various chafers, that do so much damage to lawns. It is C-shaped and has a brown head and a cream-colored body. To tell if you’re looking a Japanese larva or one of the other white grubs, you’d have to carefully study the arrangement of the hairs on its rear end, which I know you’re not going to do. At any rate, you don’t want any of these grubs in your lawn and the same techniques used to control one will get to the others.

The adults emerge in late June or July and feed on low-growing plants at first, then migrate to the top of trees, eating their way down. Even when they reach shrubs, perennials and the like, they tend to stick to the top of the plant, as they prefer sun to shade. In fact, you won’t find much Japanese beetle damage in a forest: it just isn’t their thing,

After a few weeks of making your plants look like they were repeatedly blasted with a shotgun, the female begins laying eggs in the ground, almost always in lawns or grassy fields. She lays a few eggs every few days over a 6 to 8 week period, burrowing down a few inches. When the grubs hatch, they feed off grass roots. In the fall, they dig further down, 6 inches (15 cm) or so, to keep from freezing in the winter. They’ll go even deeper in really cold climates, about 14 inches (35 cm), although that isn’t always enough and in some areas, a really cold winter can seriously deplete the population.

The grubs, now quite large, move back nearer to the surface up in the spring and do most of their damage then, leaving dead brown patches on the lawn. Then they pupate for a few weeks and emerge as adults to start another cycle.

Two Important Details

First, although Japanese beetles may have you mostly wailing about damage to your hibiscus and cannas, you have to understand that they are very much linked to lawns, and grass lawns at that. Without large and abundant lawns of grass for their grubs to feed on, they wouldn’t be numerous enough to be a major pest. In Japan, where they are native, other forms of plant far outnumber lawn grasses and as a result Japanese beetle are just a minor pest. In North America, with it’s endless green carpets of nothing but grasses, much more space is devoted to lawns than to other cultures, resulting in huge numbers of grubs turning into equally numerous and very hungry adults that have to concentrate on what little other above ground vegetation you left have to offer. It’s a bit like you invited 20 people to the salad bar, but 90 showed up. There ain’t going to be much left over!

Mommy beetles prefer to lay their eggs in lawns growing in full sun and in sandy soil. The patchier and more open the lawn (often the case in sandy soils), they better they like it. They don’t particularly like dense green lawns or tall grass. Already if you just cut back on mowing in July and August, letting the grass grow to 4 to 8 inches (10-20 cm), rather than scalping it in the typical suburban fashion, it helps discourage the females from laying eggs. Of course, they can and do fly, but still tend to remain fairly near their favorite sandy lawns.


Japanese beetles are gregarious: you rarely see just one.

Equally important to understand, though, is that Japanese beetles are extremely gregarious. They are aggregate insects, drawn to other Japanese beetles by their scent. You rarely see just one, but rather dozens, often 2 or 3 or more right on top of each other copulating. And that can be good news for a gardener. If you are diligent in your control at the very beginning of the season and keep the numbers low, the remaining JBs may quickly move on to smellier pastures.

Control Methods

People, this isn’t a war and you aren’t going to win it. But what you can do is to keep the population low enough that little damage is done. And here are some possibilities.

1. The single best practice is to gradually remove, over a number of years if necessary, the most severely affected plants and to replace them with plants they like least. This is not only amazingly effective, but also self-sustaining. No food plants, no FBs: it’s as simple as that. The problem is that many of their food plants are big trees, something you’re unlikely to want to remove… until you’ve seen them defoliated 3 years in a row. That may change your mind!

2. As soon as the adults start to appear (late June, early to mi-July), start hand harvesting them. Do so in the morning, when they’re still sluggish. Just knock them into pail of soap water: you don’t actually have to handle them. Or harvest them with a portable vacuum. This can work amazing well if you start early and keep at it. This is the second best method of controlling them.


Japanese beetle pheromone trap.

3. Use Japanese beetle pheromone traps. They’re widely available and quite effective… if you use them correctly. They contain two pheromones: a sex pheromone that mimics the smell of the female Japanese beetle, which attracts male beetles, and another that gives off a floral scent that attracts both sexes. But you have to make sure you place these traps far from any of their favorite plants. You see, the odors waft over a considerable distance, drawing them from afar, but only a handful make it into the trap. So put the traps at least 50 feet (15 m) from their favorite plants. And empty the traps daily if they start to fill up. (Sometimes they’ll catch hundreds a day.) For more information on pheromone traps, read Love Trap for Bugs.

4. You could also try spraying. Do so early in the morning, before pollinators and other beneficial insects are around. For an organic choice, you could use insecticidal soap, neem or pyrethrum. Avoid the dishwater detergent: it’s toxic to many plants. There are also systemic chemical pesticides you could theoretically use that make the whole plant toxic from the tip of its roots to the tip of its stem, but do you really want to live in an environment where you don’t dare have kids over for fear of poisoning them? Many of the best systematic pesticides are no longer offered because of their great toxicity or only professionals have access to them. Rightly so, in my belief.

5. Mix clover into your lawn or even replace your lawn grasses with a clover lawn. Neither grubs nor adults will touch clover. Egg-laying mommy JBs will tend to go elsewhere when the lawn is mostly clover.


Don’t direct any lighting to the lawn: it will show the beetles where to dig!

6. Avoid lighting lawns and flowerbeds at night. The light attracts Japanese beetles just at the right time for egg laying: it’s like telling them: dig here! Use just enough lighting for safety purposes and try not to direct any towards the lawn itself.


You can find beneficial nematodes in most garden centers.

7. You can also treat your lawn with beneficial nematodes – microscopic predatory worms – from mid-August to early September, when the grubs have just begun to hatch and are still vulnerable. Nematodes are sold alive, but refrigerated: you have to keep them cool until you apply them. Give the spot a thorough watering the day before you apply them, then apply them as a liquid spray (shake the container frequently). And water again to settle them in. Keep the soil moist for 4-7 days. Full sun when you spray them can kill them, so it’s best if you apply them on a gray or cloudy day, or early in them morning so they can burrow out of sight before the sun gets hot.

8. There is a bacterial disease you can apply. It’s called milky spore disease (Paenibacillus popilliae, formerly Bacillus popilliae). It is specific to Japanese beetle grubs and will harm no other insect. You apply it a bit like nematodes (but follow the specific instructions given). It has a greater persistence than nematodes, which tend to be rather fragile, and can remain active in the soil for up 20 years or more! However, it takes 2 to 3 years before the amount of spores in the soil builds up to the point where you start to see a difference, so you have to be very patient. Milky spore disease has never been approved for Canada and is not available there.

9. There is also a special form of BT called BTG (Bacillus thuringiensis galleriae), a bacterium that is specific to beetles, chafers and their ilk, that has recently been approved for use in North America. It is effective against all stages of Japanese beetles, both grubs and adults, and seems very promising. It is being sold under such branch names as Grub B Gon Max, grubGONE!®, beetleGONE!®, BeetleJUS! and grubHALT!®,


Shrews are interesting Japanese beetle predators.

10. Encourage the presence of natural predators (toads, birds, shrews, moles, etc.) or release ducks or chickens in the area. Skunks also eat the grubs… but do a lot of damage to the lawn while looking for them. Two natural predators of Japanese beetles from Asia have been released in the United States, the predatory fly Istocheta aldrichi and the tiny wasp Tiphia vernalis, and are spreading on their own. I don’t believe you purchase them at this time, but if they have reached your neighborhood and you want them to work for you, you’ll have to avoid using insecticides.

11. When it comes to vegetables and small fruits, you can get really good protection by simply covering them with a floating row cover. Apply it early in the season, before you seen any adults.


Castor bean is said to poison Japanese beetles: they munch on the leaves, then keel over!

12. You could try poisoning your beetles with toxic plants. They’re said to be susceptible to the flowers of the zonal geranium (Pelargonium x hortorum) and bottlebrush buckeye (Aesculus parviflora) and the leaves of castor bean (Ricinus communis) and four-o’clocks (Mirabilis jalapa). Of course, this treatment will only work if the beetles nibble on them, so you’ll be sacrificing these plants to the cause. These trap crops are not going to solve your JB problem, but it can be quite satisfying to watch the beetles drop off the plants mentioned, land on their back and twitch drunkenly. At best they’ll combine with other methods to help lower the population.

12. Other plants are reputed to repel Japanese beetles, particularly alliums (onion, leek, garlic, chives, etc.), rue (Ruta graveolens) and tansy (Tanacetum vulgare). The idea is to plant them around susceptible plants and they should keep the beetles at bay. However I hear both positive and negative results with this method, which is why I put it last. Besides, tansy is a very invasive, hard-to-control plant. Not something you’d want to let loose just anywhere!

Few Perfect Solutions

As mentioned, you won’t really be able to totally control Japanese beetles once they have found your neighborhood. The best you can do is to reduce their numbers to more acceptable levels. Only replacing beetle favorites with plants they simply don’t eat will really solve your problem completely… but by carefully combining different methods, you can reduce the population to the point where the beetles become more a small inconvenience than a scourge.

I’ll let you choose the methods you feel will work best for you.20160721C