Insects go through either three or four stages of metamorphosis. In gradual metamorphosis, eggs hatch nymphs, but in complete metamorphosis, eggs hatch larvae.
Healthy garden soil is home to billions of microorganisms and hundreds of macrofauna, including earthworms, ants, springtails, and spiders. Soil is also a nursery for insect larvae, future pests of your garden plants. White worms in soil are rarely a good sign for your garden’s future.
Table of Contents
- Possible White Worms in Soil
- Pot Worms or White Worms
- Fungus Gnat Larvae
- White Grubs
- Managing White Worms in Indoor Plants
Fortunately, recognizing larval types can help you deal with them. This article will help you identify the white-worm-in-soil identity and how to deal with it.
Possible White Worms in Soil
(Japanese beetle, May/June beetle, European Chafer, Northern Masked Chaver)
|The larvae of the Japanese beetle and June grubs (May beetle) feed on tuft roots and other organic soil material.|
|Feed on seeds, roots or decaying wood|
|Feed on plant roots|
|Weevil Grubs||Their underside is usually flat with a rounded, hump-back upper side|
|Midge Larvae||They are immature gnats and flourish in moist organic waste.|
|Mosquito Larvae||These larvae live in still water and have a breather tube on their backs|
|Fungus Gnat Larvae||Resemble midge larvae but without fleshy legs fore and aft. They live in moist soil rich in organic matter.|
|Soldier Fly Larvae||More common in compost piles.|
|Crane Fly Larvae||These gray larvae live in decaying organic matter|
|Live in long-standing stagnant water.|
|Fly Maggots||Blowfly, housefly, and fruit fly maggots have no head and cream to the white body tapered at the head and blunt at the rear.|
|Pot worms||Family to earthworms but prefer acidic, moist soil|
Pot Worms or White Worms
Pot worms (Enchytraeidae) are related to the earthworm but are much smaller and white. These tiny white worms don’t grow more than an inch long but are generally discovered when they are much smaller – hardly visible to the naked eye.
Tiny White Worms
Because they are white, pot worms are often mistaken for larvae. They are sometimes called white worms and look like white threads in soil. Despite their small size, pot worms are important contributors to soil porosity through their burrowing behaviors.
Various pot worms are commonly found in moist soils of temperate regions, especially within compost piles or houseplant potting soil. Pot worms are often a challenge to vermicompost farmers that find them in their worm bins, especially in winter.
Most pot worm species prefer acidic damp environments. A soil pH below 5.5 is ideal for these harmless soil engineers. The pot worms’ diet is similar to earthworms, and these tiny little worms also feed on fungal hyphae, bacterial material, and the excreta of another soil-borne macrofauna.
Like earthworms, pot worms are effective at decomposing organic material and aerating soil. These tiny white worms also help balance the risks of root lesions- and parasitic nematodes as they feed on them. The role of macrofauna in garden soil cannot be overstated, and these tiny white worms are an asset.
They are also prolific breeders, and populations can grow as high as 25,000 per square foot. That’s a LOT of tiny white worms.
Managing Pot Worms
If you find these tiny white worms disconcerting, solutions include adjusting your soil pH and ambient temperatures and ensuring your soil moisture levels aren’t too high. Please don’t use insecticide to manage these tiny worms that want to do nothing but improve your plant’s soil health. Though hardly appealing, the pot worm is quite harmless.
Fungus Gnat Larvae
Before we get their offspring, let’s consider the pests that love to fly into your face – the fungus gnat. I explore why they do that in a separate article (an interesting read).
In summary: They follow the carbon dioxide you exhale because decaying organic matter also releases CO2. Because they only live for a week, fungus gnats are either mating or looking for a place to lay their eggs.
High CO2 levels on the garden soil surface indicate fertile soil housing an ample, diverse population of microorganisms, i.e., food for hatching fungus gnat larvae. The name fungus gnat, incidentally, refers to their food, not their species.
Managing Fungus Gnat Larvae
A week after the mother gnat has laid her eggs, a fungus gnat larva appears that will feed on microorganisms and plant roots. Unlike other midge larvae, they do not have a single fleshy leg at the front and back of their bodies. The larvae live the longest – about a month.
You can shorten the lives of these white worms with predatory mites. The Stratiolaelaps scimitar preys on gnats’ larvae and insects in your garden, and you can order these soil mites from your local plant store.
Bottles have about 25,000 mites in them and are an effective solution to gnat-infested soil. For more info, check out this post: What Are Fungus Gnats? How To Get Rid Of Them Easily
Wireworms are the larvae of several species of click beetles (Elateridae) and primarily feed on grasses and beans, beets, cabbage, carrots, lettuce, onion, peas, potatoes and radishes.
Wireworms are thin, jointed, shiny pale white to reddish-brown, worm-like larvae resembling mealworms. They range between a quarter of an inch to an inch-and-a-half (7 to 37 mm) long and a width of an eighth-of-an-inch (3 mm) wide.
The ornamentation on the last segment of their bodies allows you to differentiate the species. Adult wireworms (click beetles) are hard-shelled, black or brown beetles that click when they right themselves after being overturned.
Wireworms cause the most damage in poorly drained garden soil, particularly in the first four years of a new bed. The best solution is precautionary; don’t overwater the plant’s soil and boost young plants’ resilience.
There are no wireworm-specific biological control methods. Good management practices are the best route to limiting pest and disease risks. these include:
- Optimizing plant soil drainage by adding compost soil amendments.
- Repot at least every two years in houseplant pots, replacing old soil with clean soil.
- Optimize seedling health using inert growing media (perlite, pumice, vermiculite, expanded shale), keeping plant soil moist and temperatures in the 77°F (25°C) range and ensuring there’s sufficient light.
- Avoid planting or transplanting too early. Avoid cold garden soil. Late planting accelerates germination, allowing plants to establish quickly and reducing the time plants are in the early stages of growth, where wireworms can cause severe damage.
- Reduce risks by rotating crops, avoiding planting crops from the same family in the same beds in consecutive years. For instance, follow Solaracea (tomatoes, potatoes, eggplant, peppers) planting with Fabaceae (peas, beans). Pathogens are common to most plants in a family but don’t infest plants from other families. Rotation helps plants thrive, and thriving plants are more resilient to attacks.
- Indoor plants are less susceptible to wireworms, but check your houseplant soil for other infestations. Potted plants are more susceptible to insects drawn by bright light, like midge and gnats. Again, healthy plants are more resilient. Such plants can successfully defend themselves against pest attacks and diseases.
- Diligently control weeds where you’re growing vegetables. Weeds reduce airflow and compete for nutrients but also host pests.
- If your garden soil shows a high worm population, excluding either pot worms or earthworms, then allow the bed to be dormant for a year. Plant a legume cover crop (alfalfa, hairy vetch, crimson clover, white clover) to boost nitrogen fixation and control the worm population. While they are unsightly, white worm colonies are not a threat.
These white worms have pale, C-shaped bodies, orange heads and three pairs of legs and can vary in size from less than a quarter inch long to over an inch. White grubs are a particular problem for turf, where their chewing mouthparts are used to feed on plant roots.
When these white worms are abundant, they can cause significant damage resulting in irregular brownish patches on turf. Additional damage can be caused by skunks, crows and raccoons as they dig into the turf to feed on these white worms.
There are several species of white grubs, and the most common ones are the larval stages of scarab beetles, such as Japanese beetles, June beetles, European chafers, and northern masked chafers.
Grubs also feed on the roots of vegetable transplants and ornamental plants. Most severe plant injury is caused by large (third stage or instar) grubs feeding on roots in the fall and spring.
White grubs are frequently encountered tilling garden soil or b sifting through the garden soil underneath damaged turfgrass. Adults can be abundant around lights in the spring of the year.
Managing White Grubs
Biological insecticides to manage grubs include Bacillus thuringiensis galleriae, Paenibacillus popilliae, Metarhizium anisopliae, and Heterorhabditis bacteriphora. Though these products may provide variable control compared to chemical insecticides, they are a healthier option. Consult product labels for application instructions and timing.
Other Control Option
An organic remedy for these white worms includes spreading diatomaceous earth around new plants, floating row covers over other healthy plants, and using natural predators like those mentioned above.
Factors That Increase Risk
Several factors can increase the risk of white grub infestations, including fields that have recently been pasture often see high populations of true white grubs. Garden soil recently converted from lawn also may host these white worms. Soil plays a significant role in infestations.
Not all worms in soil are bad, and if there’s no evidence of plant damage, you can leave them be. Using pesticides has a broader impact on soil health and should be an absolute last resort.
The rootworms typically appear in cucurbits in the middle to late season, damaging pumpkin and winter squash plants and fruits. The adult striped cucumber beetle feeds almost exclusively on cucurbits, including cucumber, cantaloupe, winter squash, pumpkin, gourd, summer squash, and watermelon.
The spotted cucumber beetle feeds on beans, corn, and potatoes. Both feed mainly on the leaves, pollen and flowers, but they feed on soft fruits, leaving scars. The beetles can kill or severely stunt young plants by girdling stems by gnawing on the tender shoots of seedlings.
These two species of beetles are also vectors of the squash mosaic virus and the pathogen that causes bacterial wilt of cucurbits, Erwinia tracheiphila. The bacterium overwinters in the gut of some striped cucumber beetles and/or in the sap of alternate host plants.
Once acquired, the bacterium is spread through their feces or on their mouthparts. When they feed on the leaves, they create openings for the pathogen to enter the plant. Once inside, the bacterium multiplies in the xylem vessels, creating blockages that cause rapid wilting and death of the plant.
There is nothing that can be done to save an infected plant. Since other cucumber beetles can pick up the bacterium from infected plants and move it to other plants, remove and destroy any wilted plants. Bacterial wilt is most severe on cantaloupe and cucumber, less on squash and pumpkin, and rarely affects established watermelon plants.
Seedlings are more susceptible both to feeding damage and infection by bacterial wilt. Covering the young plants with a floating row cover is an effective means of excluding cucumber beetles and preventing bacterial wilt of cucurbits in home plantings.
Managing White Worms in Indoor Plants
If white worms infest your potted plants, you have several options available to deal with the pests:
- Check new plants for infestation before you bring them indoors
- Happy and healthy plants are less susceptible to pathogens and pests. Make sure you don’t overwater your plants and that they get adequate light. Humidity levels are important and excessive humidity is a risk. Such high humidity conditions cause white worms to thrive in houseplant soil.
- Potting soil should be replaced every second year. Fresh soil allows you to redefine drainage profiles and improves root health (prevent root rot)
- Flushing with a very diluted hydroperoxide solution – check out my How to Get Rid of Fungus Gnats with Hydrogen Peroxide article.
I trust that you enjoyed this article and that it’ll help you manage any white worms, harmful or not. If you want more quality, helpful articles send to your inbox, share your email below.[mailerlite_form form_id=5]