Mealybug

Cryptolaemus + parasitoids.

Mealybug control focuses on beetle releases and hotspot treatment...

About Mealybugs

Mealybugs are a major pest of ornamentals, protected edible crops and houseplants across UK horticulture. These soft-bodied insects hide in leaf axils, stems and roots, feeding on plant sap and producing large quantities of sticky honeydew. Their waxy coating protects them from sprays, making biological control a critical part of any long-term management strategy.

Symptoms of Mealybug Damage

• White, cotton-like clusters on stems, leaf joints and undersides
• Sticky honeydew on leaves and benches
• Sooty mould growing on honeydew deposits
• Distorted growth and reduced vigour
• Root mealybugs causing slow establishment and yellowing
• Presence of small, wax-coated insects and egg masses

Why Biological Control Works

Mealybugs have multiple life stages that are vulnerable to predators and parasitoids. Biological agents can access the tight spaces mealybugs occupy, where chemical sprays often fail. Cryptolaemus montrouzieri (the “mealybug destroyer”) is highly effective against hotspots, while parasitoids such as Leptomastix dactylopii and Anagyrus vladimiri provide excellent long-term suppression when used preventatively in warm environments.

Common UK Mealybug Species

• Pseudococcus viburni (Viburnum mealybug)
• Pseudococcus longispinus (Long-tailed mealybug)
• Planococcus citri (Citrus mealybug)
• Rhizoecus spp. (Root mealybugs)

IPM Recommendations

• Introduce parasitoids preventatively in warm glasshouse crops
• Release Cryptolaemus into hotspots for rapid knockdown
• Avoid over-fertilising with nitrogen, which encourages soft growth
• Improve airflow around plant canopies and reduce excess humidity
• Isolate and treat heavily infested plants promptly
• Use yellow sticky cards to monitor flying male mealybugs

Preventative vs Curative Strategy

Preventative: Release parasitoids such as Leptomastix and Anagyrus early in the crop cycle when temperatures are above 18–20°C. These species establish well in ornamental crops and provide long-term control.

Curative: Deploy Cryptolaemus montrouzieri adults or larvae directly onto mealybug clusters. They are highly mobile and quickly locate infestations, making them ideal for cleaning up hotspots in conservatories, citrus, tropicals and ornamentals.

Environmental Notes

• Cryptolaemus performs best at 22–28°C and is slower below 18°C
• Parasitoids require stable warm conditions for best establishment
• Root mealybugs need soil-based biologicals such as entomopathogenic fungi or nematodes
• Dense canopies can hide infestations — regular inspection is essential