SATI Beyond The Bunch 4th Quarter 2025

ADOBE STOCK

Adult lacewings feed on pollen and nectar but their larvae are generalist predators.

Green lacewings ( Chrysoperla species) differ from the beetles in that only larval lacewings are predators. Adult lacewings feed on pollen and nectar. However, lacewing larvae are indiscriminate feeders, eating many soft-bodied pests, including red spider mites, aphids, scales, and mealy bugs. They will even eat each other if other food is scarce. Timing of releases The timing of releases should be guided by the block’s history and monitoring data. Releases should ideally start once trap catches and scouting observations indicate that pests are present. Mark mealy bug hotspots to ensure optimal placement of parasitoid and predator releases. A rule of thumb for vine mealy bug parasitoids is three releases from November to January. There is no point in releasing parasitoids if there are no hosts for them, but stopping the first wave of crawlers is crucial to prevent mealy bug infestations in bunches, so conscientious scouting matters. Although early parasitoid releases are more effective than late releases, in practice, parasitoid releases will usually be delayed by thrips control programmes. Coordinating releases with the spray programme is essential. Reputable biocontrol suppliers assess the sensitivity of their parasitoids and predators to registered pesticides and can advise on the likely impact of applications and residues. Postharvest releases are potentially valuable, espe cially in problem blocks. Postharvest spray applica tions may seem an easier option, but keep in mind that these pesticides will also significantly reduce natural predators and parasitoids and can exacer bate some pest infestations. Releases become less effective once temperatures drop below about 20 °C.

Tips for successful releases Most suppliers provide the predators and parasitoids in small dispensers packed in a cooler box. Keep the box in a cool room. Do not refrigerate the box, but replace the ice pack if necessary. It’s obviously best to hang out the dispensers sooner rather than later, but they should keep for 3–5 days. During warm weather, place them out early in the morning or late in the afternoon rather than at midday. Spread the dispensers evenly throughout blocks, but target hotspots if present. Hang dispensers horizontally in the bunch zone. Avoid exposing them to direct sunlight. Remember to open the dispensers. Some have exit holes covered by a sticker, and others have lids. Remove the lids entirely as they can sometimes close again. Parasitoid and lacewing adults require pollen and nectar. Flowering cover crops are ideal but often absent during the season. Flowering plants at the head of rows can be a good substitute. Examples include alyssum and herbs in the mint family, such as basil, oregano, sages, thymes, and wild dagga ( Leonotis species). Plants on the vineyard floor or at the head of rows also provide shelter and potentially offer a slightly cooler microclimate during the hottest part of the day. Many pests tolerate dust, and some, such as red spider mites, seem to relish it. Parasitoids and predators, in contrast, avoid dust. Dust reduction is therefore essential for successful pest control. Leaf removal and summer pruning improve predator and parasitoid efficacy because it’s easier for these insects to find the mealy bugs. For the same reasons, correct bunch spacing facilitates mealy bug control.

BEYOND THE BUNCH • 9 • QUARTER 4 • 2025