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Thripobius javae adult wasp
Source: Lisa Jamieson Biocontrol agent:
Thripobius javae wasp
Target pest:
Greenhouse thrips
Heliothrips haemorroidalis
What does the Thripobius wasp look like?
The adult Thripobius wasp is only 0.6 millimetres in length, about half the size of the adult thrips.
What about its life cycle?
It lays individual eggs into the first and small second stage thrips larvae. The wasp larva feeds inside the thrips larva until the prepupae stage of the thrips (about 11 days). It then takes over the entire body of the thrips and forms a black coloured pupa. This stage is completely stationary and the parasitoid is quite protected.
After another 11 days the tiny adult wasp emerges from the pupa and begins hunting for thrips larvae in which to lay eggs. The adult wasps only live for 3-4 days and most of the eggs (approximately 40-60) are laid on the second day.
Where are they established?
Currently, the wasp is found in Northland in the regions of Taipa, Mangonui, Kapiro, Kerikeri and Maunu in Whangarei.
When and how are they best harvested for redistribution?
Look on the underside of leaves of acmena for greenhouse thrips (the leaves have a silvery appearance) and the black Thripobius pupae. A cluster of pupae about the size of a twenty-cent piece equals about 50 individuals. It is best to release the larger clusters of pupae.
Check that the pupae have not already emerged by gently brushing a sample of pupae with a fine artist's brush. If the pupae come off as solid individual black cylinders they have not emerged. If they flake into lots of small pieces they have already emerged.
Release pupae attached to the acmena leaves. Spread the parasitoid pupae evenly through thrips infested trees or bushes. Start with blocks or trees with a history of bad greenhouse thrips damage.
About the target pest
Greenhouse thrips damage plant cells by rasping them open and sucking them dry, often resulting in leaves with a silvery appearance. The adult greenhouse thrips has cream-coloured wings and legs. Freshly emerged adults have light yellow to orange abdomens that harden and turn dark brown/black after 24 hours. The adults are all females and reproduce without males.
The adults oviposit (lay eggs) under the surface of the leaf or fruit. Adults cause considerably more damage to fruit than larvae.
A tiny larva hatches from the egg, feeds and grows through two larval stages. Both larval stages carry a ball of liquid excrement (faecal droplet) on the tip of their upturned abdomen, which gives them their name – haemorroidalis.
The subsequent stages, prepupae and pupae, both have wing buds and are non-feeding and largely motionless unless disturbed. They stay as pupae for about 4 days before moulting to become adults. Greenhouse thrips are very unusual in that they pupate on the host plant rather than in the soil like most other thrips species.