The most dangerous thing about soil pests is that they work in secret. They eat the roots and cut seedlings off from beneath the soil surface, and by the time symptoms such as wilting and yellowing show on the leaves, the damage started weeks earlier.
In this guide we get to know the most important soil and root pests in fields, greenhouses and gardens, how to detect them before they get worse, and the general steps for control and prevention. Each pest has a detailed article, and you will find its link under its name.
Quick Overview
Key pests: White grubs, mole crickets, wireworms, fungus gnats and nematodes.
Affected crops: Vegetables, turfgrass, root crops, seedlings, potted plants and ornamentals.
Symptoms: Wilting and stunting with no visible cause, yellowing leaves, eaten or swollen roots, and seedlings that are cut off or pull out easily.
Most important step: Inspect the roots and soil at the first unexplained wilting, before any treatment.
What Are the Types of Soil and Root Pests?
These pests differ in size and in the way they cause damage, but they share one thing: they live in or around the soil:
White Grubs
Thick white C-shaped larvae that feed on the roots of turfgrass and vegetables, so the turf peels away and the plant weakens.
Mole Cricket
An insect with strong front legs that digs tunnels under the soil surface and cuts roots and seedlings.
Wireworm
Hard, slender brown larvae that bore into tubers, roots and the seeds of newly planted crops.
Fungus Gnats
A small insect that appears near damp potted plants, and whose larvae feed on fine roots and organic matter.
Nematodes
Microscopic worms that live in the soil and infect roots, causing galls and swellings and weakening the uptake of water and nutrients.
How Do I Recognize Soil and Root Infestation?
Gently pull up the damaged plant and inspect the roots and the surrounding soil before deciding on treatment:
- Plant wilting even though watering is adequate, improving slightly at night and returning in the daytime.
- Yellowing of the lower leaves and stunted growth.
- Roots that are eaten, cut or covered with galls and swellings.
- White or brown larvae in the soil when you dig around the roots.
- Tunnels or raised soil on the surface, or dead patches in turf that lift like a carpet.
- Small insects flying around pots when you move the plant.
Ask for an analysis of a soil and root sample if the cause remains unclear, since some symptoms resemble fungal root diseases.
What Damage Do Soil and Root Pests Cause?
- Weakened roots, so the uptake of water and nutrients falls.
- Death of young seedlings and gaps in the planted area.
- Deformed tubers and stored roots, and loss of their market value.
- Opening wounds that fungi and bacteria enter, causing root rot.
- Difficulty of detection, so treatment is delayed and losses grow.
How Do You Tell Soil Pests From Root Diseases?
- Sudden wilting of plants in patches of the field despite adequate watering usually points to a root problem.
- Pulling up an affected plant reveals gnawed roots, white larvae or galls on the roots, which differs from fungal rot that leaves a brown color and softness.
- Small seedlings that fall over at soil level may be victims of the cutworm or the wireworm.
- Inspecting before planting by digging small soil samples reveals the infestation early.
A Preventive Plan Before Planting
- Turn the soil and expose it to the sun before planting to reduce larvae and dormant stages.
- Rotate crops and do not plant the same crop in the same spot season after season.
- Use healthy seedlings from a reliable source.
- Treat the soil or root zone with the appropriate product when needed and according to the directions written on the label.
- Keep irrigation regular without waterlogging, since saturated soil encourages fungus gnats and root diseases.
Common Mistakes in Controlling Soil Pests
- Treating the leaves only while the problem is in the roots.
- Waiting until the plants die before inspecting the soil.
- Overwatering and using undecomposed organic matter.
- Planting the same crop repeatedly in infested soil.
How Do I Get Rid of Soil Pests?
Treatment is harder here because the pest is hidden, so it matters to choose the method after identifying the species accurately:
- Identify the pest first, since treating larvae differs from treating nematodes or fungus gnats.
- Turn over the soil and inspect it by hand, and remove visible larvae in small areas.
- Use yellow sticky traps to reduce adult fungus gnats in pots.
- Biological control agents such as beneficial nematodes and beneficial fungi can be used within an integrated program.
- When a pesticide is needed, choose a product registered for this pest and crop, and follow the label directions and the pre-harvest interval.
- Re-inspect a few weeks after treatment to make sure the infestation has stopped.
How Do I Keep Soil Pests From Coming Back?
- Regulate irrigation and do not leave the soil constantly wet, since excess moisture attracts fungus gnats.
- Rotate crops and avoid planting the same host in the same place for several seasons.
- Plow the land and expose it to the sun before planting to reduce larvae and nematodes.
- Use clean, inspected soil and seedlings, and sterilize farming tools and pots.
- Get rid of old crop residues and infected roots after harvest.
- Keep soil drainage good and avoid excess undecomposed organic fertilizers.
If you are not sure of the cause of the plant wilting or need a plan that suits your soil, contact Orkida Agri engineers via WhatsApp and send clear photos of the plant and roots, and we will guide you to the right step.
Image source: Shutterstock
Frequently Asked Questions About Soil and Root Pests
How do I know the problem is in the soil and not in the leaves?
Pull up an affected plant and inspect its roots. Gnawing, larvae, galls or rot in the roots indicate that the problem is in the soil.
Is treating the soil surface enough?
Sometimes it is not enough, since some pests live at different depths, so the treatment method differs depending on the pest and the crop, and it is best to follow the product directions.
Do soil pests occur only in greenhouses?
No, they appear in open fields, greenhouses and gardens, but high humidity and repeated planting increase them.
When do I treat the soil?
It is best before planting or at the start of the season, because treating the soil after the roots have been badly damaged is less useful.