SATI Beyond The Bunch 4th Quarter 2025

LIAAN JANSE VAN VUUREN

MEALY BUG BIOLOGY

A 103-million-year-old fossilised leaf from Nebraska bears an imprint that would be instantly recognisable to any present day table-grape grower: a female mealy bug. These small sucking insects evolved over aeons to exploit a wide range of plants and are now ubiquitous agricultural pests.

BY ANNA MOUTON

Table-grape vineyards are suitable mealy bug habitats because the vines provide nutritious sap to support mealy bug reproduction during summer. Understanding their biology is the first step toward successful control.

What are mealy bugs? Mealy bugs are soft scale insects. Adult female scale insects are sedentary and depend on their waxy coating and cryptic habits for protection. Like all bugs, mealy bugs have piercing-sucking mouthparts to extract phloem from their hosts. Modern mealy bugs comprise more than 2 000 species, but this newsletter focuses on the vine mealy bug ( Planococcus ficus ), the most common species in South African table grapes. It is widespread internationally and exotic to South Africa.

Mealy bugs cause three problems The most common impact of mealy bugs is on grape appearance. Mealy bugs produce a sugary fluid called honeydew, which serves as a substrate for sooty mould. Unsurprisingly, consumers find mealy bugs, sticky honeydew, and the associated black mould off-putting. Heavy mealy bug infestations can also damage leaves and bunches, leading to browning, wilting, and desiccation. Premature leaf drop can occur. The vine mealy bug is the primary vector of grapevine leafroll-associated viruses. Infection with these viruses reduces grape yields and quality and shortens the productive lifespan of vineyards.

BEYOND THE BUNCH • 4 • QUARTER 4 • 2025