SATI Beyond The Bunch 4th Quarter 2025

BRAHM JONKER

Besides the mealy bug husks, scouts should also observe that honeydew secretion has stopped. Scouts should see predators feeding, especially the larvae, as these can’t fly away. Be warned that larval Cryptolaemus look a lot like mealy bugs, highlighting the importance of well-trained and experienced scouts. Trouble-shooting Provided the guidelines above are followed, the most common reason for failure is the presence of ants in the vines. Ants love the honeydew excreted by mealy bugs and will guard them against predators and parasitoids. Ants also catch other insects for food and have even been known to invade parasitoid dispensers, de stroying the contents before a single wasp emerged. On the upside, ants do kill some pests, so ants on the vineyard floor are beneficial, but keep them out of the grapevines. Mixing parasitoid and predator releases with pesticide applications is another reason for failure. Integrated pest management is called integrated for a reason – growers should work with their crop-protection adviser to figure out how to combine biological and chemical control measures. Growers should also consult the parasitoid and predator suppliers about the suitability of biocontrol agents for their climate and crop. For example, ask about the temperature tolerance of different species. Biocontrol agents are not inexpensive, but trying to save money by reducing the number or dose of releases is a false economy.

Dead mealy bugs remain as empty husks after parasitoid adults emerge.

Is it working? Inspect the packaging and quality of your biocontrol agents on delivery. In addition to general scouting, mark at least one release spot and go back to check the hatching rate and control in the vicinity. The biocontrol agents will take at least two weeks to reduce pest populations. This should be evidenced by reduced trap catches, but evaluating predator and parasitoid activity through scouting is indispensable. Parasitoid wasps are minuscule. Scouts are unlikely to spot them. Instead, examine mealy bug colonies for signs of parasitism. Keep in mind that mealy bug colonies won’t disappear because parasitised mealy bug bodies remain behind as empty husks when the adult wasps emerge.

Ants are fierce predators in all sorts of ecosystems globally.

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BEYOND THE BUNCH • 10 • QUARTER 4 • 2025