Groundnut farming in Nigeria, Ghana, and South Africa comes with a particular set of worries that most other crops do not share. Because the pods develop underground, out of sight, you often have no idea how bad a pest problem is until harvest day when you pull up the plants and find pods that are damaged, missing, or simply not there at all.

Mole crickets sit at the top of that list of underground worries.

A farmer in Kano State planted two hectares of groundnuts and managed the above-ground pests diligently all season. His plants looked healthy right through to maturity. When he harvested he found that nearly 40 percent of his pods had been damaged or destroyed underground. The culprit was a pest he had never specifically treated for because he had never seen it. He had been farming above the ground while the mole cricket worked below it.

This article is for every groundnut farmer who wants to make sure that story does not describe their own harvest.

The Insect Living Rent-Free Under Your Groundnut Farm

Mole crickets belong to the family Gryllotalpidae. The species most damaging to African groundnut farmers are Gryllotalpa africana and Gryllotalpa orientalis, both of which are widespread across the savanna and forest-savanna transition zones where groundnuts are most commonly grown in Nigeria, Ghana, and South Africa.

They are remarkable insects in terms of their physical adaptation. Their front legs are heavily built and shaped specifically for digging, resembling miniature versions of a mole’s forelimbs, which is exactly where their common name comes from. An adult mole cricket can tunnel through soil at a rate that allows it to cover significant ground in a single night of feeding activity.

Adult mole crickets are brown, cylindrical insects between three and five centimetres long. They are most active at night and spend the daylight hours deep in their burrows below the soil surface. They are strong fliers and can disperse between fields during their nocturnal flights, which is how new farms become infested even when surrounding soil has been treated.

Their diet in agricultural soil includes plant roots, underground stems, germinating seeds, and in the case of groundnuts, the developing pods and the pegs, which are the structures that connect the pods to the main stem underground. Damage to pegs causes entire pods to detach and remain in the soil when the plant is pulled at harvest, contributing to the phantom yield loss where a plant looks productive above ground but yields almost nothing at harvest.

Damage Patterns That Tell You Mole Crickets Are Present

Because mole crickets are almost never seen during daytime farm inspections, learning to read their damage patterns is the primary detection tool available to groundnut farmers.

In the early season before pod formation, mole cricket damage appears as irregular patches of poor germination or seedling death across the field. Germinating seeds and young seedlings are particularly vulnerable because mole crickets feed on the germinating seed directly and sever the roots of young seedlings as they tunnel through the soil. Affected patches tend to be irregular in shape and scattered rather than following a row pattern, which distinguishes mole cricket damage from fungal damping-off which tends to follow rows.

Pull affected seedlings carefully. If mole crickets are responsible the roots will show clean cuts or complete absence rather than the rotting brown discolouration associated with fungal root disease.

During pod development the most diagnostic sign is the presence of mole cricket burrow openings at the soil surface. These are small round holes approximately one to two centimetres in diameter, sometimes surrounded by a small ring of loose soil pushed up from below. Probe these holes gently with a thin stick. Active burrows will show loose freshly disturbed soil at the entrance.

At harvest the damage is unmistakable. Pods with ragged feeding damage on the shell, pods with holes bored through them exposing damaged or missing seeds, and detached pods remaining in the soil after the plant is pulled are all classic mole cricket harvest damage signatures.

When and Where Mole Cricket Pressure Peaks

Understanding the seasonal rhythm of mole cricket activity helps you time your management interventions at the moments when they will have the greatest impact.

Mole cricket activity peaks during two windows in the growing season. The first peak occurs during land preparation and early planting when soil disturbance brings eggs and nymphs close to the surface and the fresh organic matter of incorporated crop residue provides an attractive food source that draws mole crickets into the field.

The second and more damaging peak occurs during the pod-filling stage when developing groundnut pods become the most nutritious food source available in the soil profile. This coincides with the period when damage is most economically significant because it directly reduces the number and quality of harvestable pods.

Mole cricket pressure is highest in sandy loam and light sandy soils that are easy to tunnel through. Heavy clay soils with poor drainage have lower mole cricket populations because the physical effort of tunnelling through compacted wet clay is too great. Farms transitioning from heavy clay to lighter amended soils may experience increased mole cricket pressure as the soil structure improves.

Mole cricket populations also build up in fields where the same crop has been grown repeatedly without rotation because the soil profile becomes familiar territory with established burrow networks from previous seasons.

Getting Rid of Them: A Layered Approach That Works

Bait Application at the Right Moment

Poison bait is the most effective and practical mole cricket control method for African groundnut farmers because it delivers the chemical directly to where the pest lives rather than relying on a soil drench to intercept tunnelling insects.

Prepare a simple grain bait by mixing 500 grams of maize bran or wheat bran with 10ml of chlorpyrifos 48 EC and enough water to make the bran moist but not wet, approximately 50ml of water. Mix thoroughly until the chlorpyrifos is evenly distributed through the bran. Allow the mixture to sit for 30 minutes before application so the chemical is fully absorbed into the bran particles.

Broadcast the prepared bait evenly across the field at dusk, just before dark, when mole crickets are beginning their nightly surface and near-surface foraging activity. Apply at a rate that distributes bait particles approximately every 10 to 15 centimetres across the soil surface. Mole crickets encounter the bait during their nocturnal movement, consume it, and die within 24 to 48 hours.

Apply bait at two critical timings. The first application at land preparation one week before planting reduces the resident mole cricket population before your crop is in the ground. The second application at the beginning of pod formation targets the population during the highest-risk damage window.

Do not apply bait before rain is forecast as moisture dissolves the bait and reduces its attractiveness and palatability to mole crickets. Apply during dry weather when the soil surface is dry enough for mole crickets to move freely.

Soil Drench at Planting

Chlorpyrifos soil drench applied into planting furrows before seeding creates a treated zone in the root development area that kills mole crickets tunnelling through it.

Mix chlorpyrifos 48 EC at 30ml per 15 litres of water. Pour the solution into the planting furrow at a rate of approximately 200ml per metre of furrow length before placing seeds. Cover immediately after application. The treated soil zone intercepts mole crickets tunnelling toward germinating seeds and young roots during the most vulnerable early season period.

For broadcasting across the full field before planting, apply chlorpyrifos 48 EC at two litres per hectare diluted in sufficient water for even distribution and incorporate into the top 15 centimetres of soil by tillage immediately after application.

The Overnight Flood Trap

This is a practical zero-cost detection and control method used by experienced groundnut farmers in northern Nigeria and parts of Ghana that works surprisingly well on smaller plots.

In the evening identify areas of the field where burrow openings are visible. Pour two to three litres of water slowly into each burrow opening until it fills completely and the water begins to pool at the surface. The flooding forces mole crickets out of their burrows within minutes. Have a torch ready and collect the disoriented mole crickets by hand as they emerge and drop them into a bucket of soapy water.

This method will not control a large population across a full hectare but it is highly effective for monitoring population levels, confirming mole cricket presence before committing to chemical treatment, and reducing populations in small high-value plots where chemical application is not desirable.

Organic Options for Budget-Constrained Farmers

Neem cake incorporated into the soil at 500 kilograms per hectare before planting creates a soil environment that repels mole crickets through the nematicidal and insecticidal compounds released during decomposition. It is less immediately effective than chlorpyrifos but contributes to the overall soil health improvement that makes the farm less hospitable to soil pests generally.

Wood ash broadcast across the field surface at a rate of one kilogram per ten square metres and incorporated lightly into the top five centimetres creates an alkaline soil surface layer that mole crickets find uncomfortable for surface movement. Apply immediately before planting and after each significant rainfall that washes it deeper into the soil.

Diatomaceous earth applied along burrow openings and across known activity zones kills mole crickets through physical abrasion of their body surface when they move through treated soil. Apply as a dry powder at the soil surface and around burrow openings. Reapply after rain.

You can also read: Termite damage in farmland and how to stop it

Crop Rotation as Your Season-Long Defence

Mole cricket populations build up over successive seasons in fields where groundnuts are grown continuously because the soil profile becomes established territory with permanent burrow networks and a reliable food source season after season.

Breaking this cycle with a one-season rotation to a cereal crop like sorghum or millet disrupts the established burrow networks through tillage, removes the groundnut food source that sustains high mole cricket populations, and allows natural predator populations including ground beetles, birds, and parasitic flies to reduce the overwintering population before groundnuts return to the field.

A simple two-year rotation of groundnuts followed by sorghum or millet consistently reduces mole cricket pressure in the groundnut year compared to continuous groundnut monoculture on the same land. It also breaks the cycle of rosette virus disease in groundnuts which shares some of the same soil environment risk factors, giving you a double benefit from one management decision.

What Goes Wrong When Farmers Fight Mole Crickets

Applying insecticide only to the soil surface without incorporating it. Mole crickets live and feed below the surface. A contact insecticide applied to the top of the soil and left there does not intercept tunnelling insects moving one to three centimetres below. Always incorporate soil treatments or use bait that mole crickets encounter during their natural movement.

Treating above-ground pest problems while the real damage is happening underground. Several farmers treat their groundnut crops thoroughly for leaf-feeding insects and achieve excellent above-ground plant health while losing significant pod yield to mole crickets underground. Scout for both above and below-ground pest pressure from the beginning of the season.

Applying bait during the day. Mole crickets are nocturnal. Bait applied in the morning sits exposed on the soil surface for the entire hot day, drying out, losing attractiveness, and being consumed by birds before mole crickets become active in the evening. Always apply bait at dusk.

Harvesting without checking detached pod loss. Many farmers count only the pods attached to the plant when estimating yield and losses. Carefully sifting through the soil in harvested rows to collect detached pods gives a true picture of mole cricket damage and helps you decide whether to intensify management in the following season.

Conclusion

Mole crickets are a below-ground problem that demands above-ground thinking and planning. You cannot wait until harvest to discover the damage because by then there is nothing left to protect.

The most important thing you can do after reading this article is walk your groundnut field or your land before the next planting and look for burrow openings. If you find them, your field has an established mole cricket population that will be there waiting when your next crop goes into the ground.

Prepare your chlorpyrifos soil drench before planting day. Mix your bait and apply it at dusk one week before planting to reduce the population before your seeds go in. Set your second bait application date for the beginning of pod formation and put it in your farming calendar now so you do not miss the window.

The groundnut pods you protect underground are the income you take to market. Treat them with the same seriousness you give to everything that is visible above the soil surface.