22-spot ladybird

Systematic position. The 22-spot ladybird (Thea vigintiduopunctata or Psyllobora vigintiduopunctata) belongs to the order Coleoptera and the family Coccinellidae. Unlike most ladybirds that prey on aphids, this specific species is a mycophagous insect, meaning it feeds on various types of fungi, specifically those causing powdery mildew.

Affected crops. This pest primarily attacks plants that suffer from fungal infections. It is commonly found on roses, various deciduous shrubs, and vegetable crops like pumpkins, cucumbers, and other cucurbits. Its presence is a clear indicator that the host plant is struggling with a fungal issue that requires horticultural attention.

Biology and life cycle. The life cycle involves a complete metamorphosis, consisting of the egg, larva, pupa, and adult stages. Both larvae and adults are active foragers during the warmer months, grazing on fungal mycelium found on the underside or surface of leaves. Overwintering occurs in sheltered areas such as leaf litter, bark crevices, or garden debris.

Nature of damage and economic importance. The damage is considered secondary. While the ladybird consumes the fungus, its movement across the leaf surface disrupts the plant's cuticle. Furthermore, by crawling over infected tissues, they can act as vectors for spreading fungal spores to healthy, uninfected leaves, exacerbating the disease problem across the crop.

Control measures. Integrated Pest Management (IPM) is the best approach for this species. Rather than targeting the insect directly with insecticides, the priority should be controlling the powdery mildew itself using fungicides or cultural practices. Reducing the availability of the fungus forces the ladybird population to naturally decline or relocate away from the garden.

• Improving air circulation around plants.
• Removing infected plant debris to reduce overwintering sites.
• Application of appropriate fungicides for mildew.
• Using biological control agents that target fungal pathogens.