Leatherjackets in Cereals: A Hidden Underground Threat

Leatherjackets, the larvae of crane flies, are a growing concern for cereal growers across the UK. In this Blog, the information focuses on the biology of this pest, what to look out for in the field, and how to manage the problem effectively before it affects establishment and yield.

What Are Leatherjackets?

Leatherjackets are the soil-dwelling larvae of the adult crane fly, commonly known as “daddy longlegs.” While the adult flies are harmless, their larvae feed below the soil surface—gnawing away at cereal roots and young stems.

They are soft-bodied, legless, greyish-brown grubs, and they’re hard to spot unless you actively dig. Their leathery outer texture is what gives them the name “leatherjackets.”

Risk Timing and Lifecycle

The problem often begins in late summer, when crane flies lay eggs on damp soil surfaces—often in pasture or grassland stubble. These eggs hatch in early autumn, and the larvae begin feeding almost immediately.

Leatherjackets feed right through winter, which is unusual for insect pests. This extended feeding period makes them especially damaging to winter cereals and newly established crops.

Identifying a Leatherjacket Problem

These are some of the symptoms that often appear before you see the pest:

• Patchy emergence in cereals
• Stunted, pale or slow-growing plants
• Crops that look grazed from below, especially in field margins and pasture-following fields

To confirm the cause, you’ll need to dig into the root zone. The larvae are often just a few centimeters below the surface.

Why Leatherjackets Are Increasing

• More direct drilling and reduced cultivation disturb soil less—great for worms, but also for leatherjackets.
• Warm, damp autumns encourage more crane fly egg-laying and better larval survival.
• Fields following long-term grass are especially high-risk.

These changing farming practices and weather trends are giving the pest a better environment to thrive.

How to Manage Leatherjackets

Management begins with awareness. Key control considerations include:

1. Field History Awareness

Fields after long-term pasture or grass leys are the highest risk. Plan accordingly.

2. Monitor and Dig

Regular root checks are essential. Waiting until damage is visible from above could be too late.

3. Establishment Strategy

Strong early establishment helps cereals better withstand feeding. Weak or waterlogged seedbeds are far more vulnerable.

4. Chemical Control?

Currently, chemical options are limited. A soil sterilant, such as Lime Sulphur, could be an option on small areas and in horticultural locations.

Final Thoughts

Leatherjackets aren’t always top-of-mind for arable growers, but they’re an underground pest with the potential to quietly reduce crop performance—especially where cereals follow grass. Vigilance, rotation planning, and soil inspections are critical steps to staying ahead of this threat.

Article by Dr Russell Sharp

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