Are Beneficial Predatory Nematodes effective in fight against slugs and grubs?

Question

I have a large population of mature slugs and grubs in my flower and vegetable garden. The slugs are approximately 2" in diameter and 4" long. The white grubs are about 2" long. I have read that predatory nematodes are effective against slugs and grubs, but am nervous about introducing a different species into the area.

Has anyone tried these?

Have they been effective?

Thank you for all your tips and suggestions. Please, only reliable and knowledgeable sources. Thanks again!!

Answer 1

As "Ed Snow" mentioned in his response, parasitic nematodes that control slugs and snails are short-lived and work best when temperatures exceed 40-degrees. Their life-span is about 6 weeks if they haven't found a host (snail or slug) to reproduce within.

The parasitic nematode of slugs -(called Phasmarhabditis Hermaphrodita), enters the slug through the slug mantle. Once inside, the nematode releases a bacterium which multiply and this is what the nematode feeds on. The nematodes multiply and within 4 to 7 days the slug stops feeding and will burrow underground to die.

These nematodes do not pose a threat to earthworms. In fact, there's no concern about beneficial nematodes becoming a problem in your garden or causing harm to your pets.

Unlike other beneficial nematodes, they have the ability to continue to reproduce successfully and remain in your garden providing there are sufficient number of snails/slugs for them to feed upon.

These nematodes arrive in small trays embedded in a powdery-like sustance that is mixed with water and then applied by using a watering can or a sprayer (with filter screen removed). They need to be kept refrigerated up until the time they are used.

There are several parasitic nematodes that prey upon specific pests found in soils; fungus gnat larvae, craneflies, black vine weevil. I've found the advantage of using nematodes is that they're able to detect grubs/larvae where most pesticides can not reach (such as within thick/dense root mass).

As for your grub problem, I'd recommend you take a couple of grubs into the nearest Farm Advisor's office to get it properly identified. He will be able to tell you if it requires control or not and advise on proper products to use.

Hope this information helps answer any concerns/questions you may have had. GOOD LUCK!

-Certified Professional Crop Consultant with over 30 years of experience and a Degree in Plant Science

Answer 2

Interesting question. They do work on grubs but application is tricky at best. The nematodes are very susceptible to UV ray damage so they need to be applied when the sun is low in the sky. Second they must have a moisture film to get into the soil. The grass must be wet and water must be applied immediately......and of course they must be applied with water. In studies I'm quite familiar with, the nematodes were comperable in grub control to chemical pesticides. Research by Ward and Blanco, NMSU around 1992.

The slug presents another problem. They are above ground creatures and remembering the UV condition, I think that could be an undoing. Unless the nematode was already within the slug, it would die just hitch hiking waiting to enter.

Also what species nematode? I wonder if the same type would inhabit both a grub and a slug?

I too would be interested in research on nematodes and slugs.

Answer 3

Predatory Nematodes

Answer 4

Nematodes like Milky Spore are effective, but it does take some time for them to become effective. It's a living thing and it has to establish itself in the soil. They don't work as quickly as insecticides. Usually by the time the grubs start feeding, it's too late to apply the nematodes. Further, previously applied insecticides can kill the nematodes, too. Bear in mind that there are other grubs than the Japanese beetle grubs and Milky spore doesn't affect them. It's not as green and environmentally friendly, but I prefer the insecticide route. It takes care of other lawn pest (ants, fleas, etc.) issues as well as the grubs, so one solution is taking care of multiple problems.

Answer 5

Nematodes can work, but often are short lived and temperature specific. Repeat applications will be needed as parasite will die without host, in severe frost, too much rain, too dry etc. "White grubs" is a vague description, and could indicate Swift Moth caterpillars. Living below ground, with a brown head and LEGS, this one is unmistakable. Not ALL "grubs" have nematode preparations for their control. Control is specific to known insect PESTS, and are NOT wide spectrum insect killers. Don`t want to exterminate Glow-worms and Stag Beetles do we !