John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org
licensed under a Creative Commons Attribution 3.0 License.
Has your garden or turf become overrun by the larvae of Japanese, June, or May beetle? Beneficial nematodes for grubs can be a cost-effective way to rid your luscious soil of these root-destructive insects and leave your turf and garden produce spruce and healthy.
What are Beneficial Nematodes?
Beneficial nematodes are small microscopic roundworms. They are often applied to moist dirt/soil to control caterpillars or grubs. These biological nematodes carry a pathogen that is injected into its host that eventually multiply and kill it.
The most common beneficial nematodes are Heterorhabditis bacteriophora and Steinernema carpocapsae. These affect different insects. Other species of beneficial nematodes have been reported, but more research is needed to assess or improve their effectiveness.
Do Nematodes Work?
Yes, nematodes do work. Nematodes vary, but those that are beneficial are known for carrying bacteria and fungi throughout the soil to infect and eliminate insects.
Beneficial nematodes for grubs (Heterorhabditis bacteriophora) are highly parasitic. Unlike other nematodes, they don’t wait for their prey to come to them. They’re called cruisers, because they move throughout the soil, locating sedentary pests like white grubs to infect.
Once these nematodes encounter their hosts, they seek an entrance, which is oftentimes body openings such as the mouth or breathing tubes. Upon entrance, they linger and release a bacterium which then multiplies.
Beneficial nematodes also begin reproducing inside the host. This eventually kills the grub in a day or two; sometimes less. The host is then converted into nematode food, and as resources deplete and overcrowding occurs, beneficial nematodes emerge from the dead host and move on to their next meal.
Nematodes for grub control are beneficial and are effective for various reasons.
1. They can be used against a wide range of insect pests.
2. Hosts of nematodes are killed within 48 hours of infection.
3. Nematodes can be bred on artificial media, which makes them readily available for commercial use.
4. Nematodes can live for months when stored under appropriate conditions.
5. For a more potent effect, nematodes can be combined with other insecticides and even fertilizers.
6. Host insects aren’t immune to the bacteria distributed by nematodes.
The Best Beneficial Nematodes for Grubs Control
The best beneficial nematodes for grub control are Heterorhabditis bacteriophora. If any other nematodes are used, you’ll not get the same effect. These nematodes are at least 96% effective when used to control Japanese beetle grubs, European chafers, and others.
Heterorhabditis bacteriophora are more effective than Steinernema carpocapsae because they sail about in the soil to search for their hosts, instead of waiting for the host to come to them. Heterorhabditis bacteriophora also has a “special tooth” that makes it easier to penetrate grubs.
When you order beneficial nematodes for grub control, they are shipped in the infective (infectious) juvenile stage of their life cycle. You may receive your nematodes in gel form, granules, sponge, or even liquid. Infectious juvenile nematodes can be stored in your refrigerator for about 2 to 3 weeks.
How Long Do Nematodes Live in the Ground
How long nematodes live in the ground depends on how favorable or unfavorable conditions are. This includes the structure of the soil, temperature, and moisture.
As nematodes are sensitive to the UV in sunlight, exposure to it could kill them in a minute or two. Hence, it’s always advised to apply beneficial nematodes for grubs to the soil early in the mornings, or late afternoons.
Nematodes are living organisms; apply them immediately after receipt. As they thrive in moist soil, ensure to irrigate the area if it hasn’t rained. You may also apply nematodes during the rain, as well. To prolong the lives of nematodes, at least long enough for them to find and kill grubs, keep the soil moist for at least 7 to 10 days, if it doesn’t rain.
Some nematodes are able to suspend their life processes under unfavorable conditions. In this state, they may survive in soils that are too parched, hot, or cold. Once conditions pick up or are favorable again, beneficial nematodes can return to life. This process is known as cryptobiosis.
This makes beneficial nematodes for grub control effective. They can be living in the soil for years and have a residual impact. As long as conditions are favorable or there remains a grub infestation, you’ll have nematodes scouting the soil in search of a host, and since they keep reproducing, it makes it difficult to get rid of them.
Can Beneficial Nematodes Infect Humans?
Group of Nematodes by CSIRO
Beneficial nematodes don’t infect humans.
Nematodes for grub control are specific, and as suggested, infect insects. These subspecies of nematodes are different than human parasites. They are entomopathogenic because they infect insects with bacteria to kill them.
Beneficial nematodes (or biological nematodes) aren’t necessarily parasitic. It’s the bacterium released from these nematodes that feed directly on the host. It is these symbiotic bacteria that are ‘true parasites’ that eventually kill the host, and then nematodes clean up by using the cadaver as their meal and breeding ground.
Once nematodes are termed beneficial, biological, or entomopathogenic, they do not cause harm to children, humans, or pets, and as such, are safe to use around them. They also won’t harm the soil.
Are Nematodes Harmful to Humans?
Yes, some nematodes are harmful to humans.
There are millions of nematode subspecies. While beneficial nematodes aren’t harmful to humans, other species are. In fact, some nematode species are human parasites.
These species include:
- Ascarids (Ascaris)
- Pinworms (Enterobius)
- Whipworms (Trichuris trichiura)
Learn how human parasitic nematodes affect humans >> Introduction to Nematodes
How are Beneficial Nematodes for Grub Control Applied?
1. Choose the species of beneficial nematodes depending on your target pest. In this case, as you’re looking to solve a bad case of grub infestation, choose Heterorhabditis bacteriophora. These nematodes search out for and infect white grubs. You can find a reputable supplier of beneficial nematodes for grubs here.
2. Only apply your beneficial nematodes when you’ve confirmed the presence and activity of grubs. White grubs are mainly active in late summer or early fall. After your initial application, a second one should follow in about 2 weeks. This will enhance the effect.
3. Resist the urge to apply your beneficial nematodes if the soil temperature is below 600F.
4. Always water or irrigate the soil prior to application. The soil should be moist, but not muddy.
5. Mix your newly acquired infective nematodes in cool, distilled water. Transfer the solution into a sprayer and then apply it to infected areas.
6. If the area in which you live is hot, apply your beneficial nematodes to the soil in the evenings or early in the mornings. Light and heat will kill nematodes.
7. The soil should be irrigated after you’ve applied your nematodes. You may need to do this several times to keep it moist.
8 Apply more beneficial nematodes a week after. To see if your application is doing what it should, infected grubs should change color. They should look red or yellow-brown.
Nematodes for Grub Control, Conclusion
Beneficial nematodes for grubs are effective when used appropriately. If your garden or turf is infested by grubs, sourcing nematodes can do all the dirty work for you. Before using your beneficial nematodes, read and follow label instructions.
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