New biocontrol agent released
The long-awaited and much anticipated new biocontrol agent,
Tamarixia triozae, a parasitoid wasp which destroys the Tomato Potato Psyllid (TPP) pest, has been released in Hawke’s Bay and Canterbury.
About 400-500 Tamarixia were released by Plant & Food Research at three sites in Hawke’s Bay in August, and a further 150 were released at two sites in Canterbury in early September. They were released onto African boxthorn plants, where overwintering populations of TPP can be found.
These initial releases are the start of a wider planned release and monitoring project, supported with funding through the government’s Sustainable Farming Fund (SFF). That project is being managed by the Vegetable Research and Innovation Board and includes Tomatoes NZ, Vegetables New Zealand, Potatoes New Zealand, the NZ Tamarillo Growers Association and Heinz-Wattie’s NZ Ltd. In June 2016, the group gained Environmental Protection Authority (EPA) approval to import and release Tamarixia into New Zealand.
Although the winter release was not ideal timing, it came about because the first shipment of Tamarixia (received from Mexico earlier this year) was found to have fungal contamination, so could not be released.
The Tamarixia project group collectively decided that they did not want to wait until spring to try and bring in another batch. We wanted to be sure that Tamarixia would be available in
time for the coming season so that the Sustainable Farming Fund monitoring and release project could get underway, and possibly have some available for others who wish to release it.
Plant & Food Research worked with the Tamarixia supplier and successfully imported a “clean” batch in July. Those individuals were reared, and the second generation “F1” progeny were those approved by the Ministry for Primary Industries (MPI) for the recent first releases in Canterbury and Hawke’s Bay. A condition of the current MPI import permit is that “imported parasitoids will be reared in quarantine through one generation, and once this is completed, all Tamarixia triozae adults from the original imported product will be destroyed”.
The project group is now looking at ways of establishing a supply of Tamarixia for this summer. One option being looked at is using the services of commercial biocontrol agent supplier Bioforce, who are interested in rearing and supplying the parasitoid. Rearing a Tamarixia colony in captivity requires a supply of live TPP and host plants, making it a little bit more difficult to supply than some other biocontrol agents, such as Encarsia, which can survive and reproduce on an artificial diet. As a parasitoid, Tamarixia needs a live TPP nymph to reproduce, meaning that a live supply of TPP is needed as part of the rearing system. The Tomato Potato Psyllid has caused enormous problems for the potato, tomato, capsicum and tamarillo growers in New Zealand since it was discovered here in 2006.
Since then, the industry has been waging a battle to control this insect pest. Tamarixia, a tiny wasp that lays its eggs on the psyllid, which then hatch and eat the psyllid, is a biological control option. Tamarixia is found in the USA and Mexico as a naturally occurring parasitoid of Tomato Potato Psyllid.
The long-term hope is that Tamarixa will establish selfsustaining populations in the natural environment, therefore reducing the presence of TPP and the pest pressure for tomato, potato and tamarillo growers throughout New Zealand.
One of the vials that contained Tamarixia triozae adults attached to African boxthorn, a host plant of tomato potato psyllid. Photo courtesy of Melanie Davidson, Plant and Food Research
Tamarixia triozae about to parasitise a TPP nymph. Photo supplied by Plant & Food Research
A healthy TPP nymph alongside a parasitized nymph (showing exit hole). Photo supplied by Plant & Food Research
One of the release sites for Tamarixia triozae in the Hawke’s Bay. The parasitoid was released near the African boxthorn, an alternative host for the tomato potato psyllid, in August 2017.