It sounds like the kind of thing that can't possibly be legal to just order online: a live parasitic wasp, delivered by courier, that you release directly into your vegetable garden. But Tamarixia triozae is exactly that, a genuine, government-approved biological control for tomato-potato psyllid, available to any New Zealand home gardener who wants it.
Tamarixia triozae is tiny, harmless to humans and pets (it cannot sting), and does one specific job: it lays an egg inside a TPP nymph, and that egg develops by consuming the nymph from within, eventually killing it. It was approved for import and release in New Zealand by the Environmental Protection Authority in 2016, following research into TPP biocontrol options, and was subsequently established here through a Sustainable Farming Fund programme that ran from 2016 to 2020, releasing the wasp at more than 30 sites around the country with Bioforce and Lincoln University supplying and monitoring it. It's now a genuinely established part of the country's TPP biocontrol picture, not an experimental one-off.
it lays an egg inside a TPP nymph, and that egg develops by consuming the nymph from within, eventually killing it
For home gardeners, Bioforce sells Tamarixia directly: about $30 NZD for a minimum order of 100 adult wasps plus GST and freight, delivered live by courier. The recommended release rates scale with how bad the problem already is: roughly half a wasp per square metre as ongoing prevention before psyllids show up, one per square metre for a light to moderate infestation already under way, and up to ten per square metre for a heavy one. They're released by hand between the leaves, ideally morning or evening rather than in harsh midday sun, and shouldn't be refrigerated, just kept cool and dark for up to two days if they can't go out immediately.
It isn't instant and it isn't total control on its own. Parasitism begins as soon as the wasps are released, but confirming it's working takes patience: a parasitised nymph turns a visible gold colour after about a week at 26°C, longer if it's cooler, which is most of a New Zealand spring. Field studies from the original establishment programme found average parasitism rates of around 15%, with a maximum of 40% in the best conditions, meaning Tamarixia is genuinely most effective as one part of a combined approach, alongside mesh exclusion and good growing conditions, rather than a single fix that replaces everything else.
What makes it worth knowing about, beyond the effectiveness numbers, is what it represents: a living, self-sustaining control that keeps working in a garden without needing to be reapplied the way a spray does, bought once from a New Zealand supplier rather than manufactured overseas. For a home gardener who's already tried mesh and is still seeing psyllid sugar on their leaves, it's a genuinely different tool to reach for, not just another bottle.