Mealybugs

Introduction

Mealybugs cause damage to several crops in the horticultural sector. The most important species occurring in the glasshouse belong to the genera Planococcus and Pseudococcus. Within the Planococcus genus, the citrus mealybug Planococcus citri is a particular problem; several species within the Pseudococcus genus occur in glasshouses.

 

Biology

The mealybug has five stages in its life cycle. The females go through the stages of egg, three nymphal stages and adult insect; the males go through egg, two nymphal stages, false pupa and adult insect. Mealybugs derive their name from the third larval stage onwards when the female's body is covered with a white wax-like substance in the form of powder, filaments, projections or plates.

 

Damage symptoms

• Nymphs and female adults feed on plant sap. This reduces growth, and causes deformation and/or yellowing of the leaf; sometimes leaves even drop off the plant. This can reduce yield or cause cosmetic damage. Infested plants often drop flowers or leaves if present.
• Mealybugs excrete honeydew, on which dark soothy moulds develops. Together with the whitewax-like secretions these soil the plants. Photosynthesis of the leaves reduces, causing the production to decrease.