Leaf Miner

Diglyphus isaea.

Leaf miners tunnel foliage; parasitoids provide biological suppression...

About Leaf Miners

Leaf miners are the larvae of small flies in the genus Liriomyza, which tunnel between the upper and lower leaf surfaces, creating distinctive winding trails. Common in UK ornamentals, salads and protected edible crops, leaf miners reduce photosynthetic area, weaken plants and cause severe cosmetic damage. Heavier infestations can lead to leaf drop, growth reduction and compromised crop quality.

Symptoms of Leaf Miner Damage

• Serpentine “tracks” or blotches inside leaves
• White or silvery trails that widen as the larva grows
• Black feeding spots from adult punctures (“stings”)
• Premature leaf yellowing and drop
• Flattened larvae visible inside the leaf when held to light
• Small yellow pupae found on soil or leaf surfaces

Why Biological Control Works

Leaf miners spend most of their lifecycle inside the leaf, where conventional chemistry struggles to penetrate. Parasitoid wasps such as Diglyphus isaea and Dacnusa sibirica are highly effective because they locate larvae by smell and movement, attacking them directly inside the plant tissue. These species provide excellent long-term suppression when used preventatively and monitored closely.

Key UK Leaf Miner Species

• Liriomyza trifolii (American serpentine leaf miner)
• Liriomyza huidobrensis (South American leaf miner)
• Liriomyza bryoniae (Tomato leaf miner)

IPM Recommendations

• Introduce parasitoids early before mines reach the leaf edges
• Remove heavily mined leaves to reduce emerging adults
• Use yellow sticky cards to monitor adult fly activity
• Inspect undersides of leaves weekly for new “stings”
• Maintain stable temperatures for optimum parasitoid activity
• Avoid systemic insecticides that suppress beneficial wasps

Preventative vs Curative Strategy

Preventative:

• Introduce Dacnusa sibirica preventatively in cooler houses where it excels at targeting early instar larvae.
• Use Diglyphus isaea to maintain low background levels across warm seasons.

Curative:

• Increase introduction rates of Diglyphus isaea when serpentine mines become visible on multiple plants.
• Remove leaves with mature mines to prevent emergence of adults.

Environmental Notes

• Dacnusa sibirica is most active in cooler environments (15–22°C)
• Diglyphus isaea thrives in warmer houses (20–30°C)
• Good airflow and light levels support parasitoid efficiency
• High leaf miner pressure often follows migratory peaks in spring and autumn