SATI Beyond The Bunch 4th Quarter 2025

Biocontrol agents Predators and parasitoids are the foundation of successful mealy bug management. In many vineyards, it’s possible to suppress mealy bugs below economic thresholds using only these natural enemies and without the need for any chemicals.

Parasitoids versus predators The parasitoids used for crop protection are wasps that lay their eggs inside pests. The developing wasp larvae consume the host from the inside. Parasitoids tend to be host-specific – they only target one insect type or species. In general, parasitoids can survive at lower pest densities than predators because the adult parasitoids feed on pollen and nectar. Each parasitoid female can lay eggs in a relatively large number of hosts, although parasitism rates vary by parasitoid species and site-specific factors. The predators used for crop protection are insects or mites that eat pests. Both larvae and adults of most predators hunt and kill prey. Predators will often feed on different prey species but may have strong preferences for particular prey. Adult predators require high pest densities. The pickier a predator is, the higher the density of its preferred prey must be. Many predators are notoriously voracious, but they still kill pests one by one, so they tend to chalk up a lower body count than parasitoids. Common commercially available parasitoids Anagyrus vladimiri and Coccidoxenoides perminutus parasitise vine mealy bugs ( Planococcus ficus ). A. vladimiri prefers third instar and adult mealy bugs, but may have a limited impact on second instars. C. perminutus only lays eggs in first and second-instar mealy bugs.

C. perminutus is more heat-sensitive than A. vladimiri . Leptomastix dactylopii will parasitise more than 20 mealy bug species, including vine mealy bugs, but prefers citrus mealy bugs ( Planococcus citri ). Therefore, it may abscond to nearby citrus rather than remain in vineyards. L. dactylopii has limited commercial availability but occurs naturally in most grape-growing regions. Common commercially available predators Cryptolaemus montrouzieri is a diminutive beetle, affectionately known as the mealy bug destroyer. Besides eating all mealy bug stages, it lays its eggs in the egg sacs of vine mealy bugs, which are devoured by the beetle larvae.

ADOBE STOCK

Mealy bug destroyers being unleashed on pests.

BRAHM JONKER

Nephus bipunctatus and other Nephus beetles are even tinier, so they can squeeze into crevices to find mealy bugs. However, because they are smaller, they eat less than C. montrouzieri and prefer smaller mealy bug life stages. Neither of these beetles is specifically a vine mealy bug predator, but adult beetles will fly away if food is scarce. They should be reserved for hotspots or severe infestations.

Mealy bugs parasitised by Anagyrus vladimiri.

BEYOND THE BUNCH • 8 • QUARTER 4 • 2025