Patches exist south of Gellibrand Hill and in Twin Dams Paddock. Patches in the back paddock appear to have been controlled with herbicide, but seed presumably remains in the soil.
Biological Control
Eleven biological control agents were released in Australia but only 6 persisted (references Agriculture Victoria and Briese 2012).
| Common Name | Scientific Name | Released | Effectiveness |
|---|---|---|---|
| St Johns Wort Leaf Eating Beetle | Chrysolina hyperici and C. quadrigemina | 1930s | effective except in shade |
| St Johns Wort Crown and Root Boring Beetle | Agrilus hyperici | 1939-40 | failed to persist in Victoria |
| St Johns Wort Gall Midge | Zeuxidiplosis giardi | 1953 | ineffective |
| St Johns Wort Aphis | Aphis chloris | 1986-87 | widespread but populations do not reach damaging levels |
| St Johns Wort Mite | Aculus hyperici | 1991 | effective at some sites but more research needed |
What appear to be St Johns Wort Leaf Eating Beetles were seen on the St Johns Wort patch pictured above. St Johns Wort plants seen in the park have had flowering stems to about 50cm high, except for a plant in the shade which was well over a metre tall.
Prior to the release of the the Johns Wort Aphis and the St Johns Wort Mite it was known that they could feed and reproduce on the native species Small St Johns Wort (Hypericum gramineum), which occurs at Woodlands Historic Park. Fortunately subsequent research has shown no significant effect on the native species (Willis et. al. 2003). The other agents were released before the passing of the Wildlife & Countryside Act 1981, so testing of their impacts on Australian species was not required. It is known that Chrysolina quadrigemina can feed on Small St Johns Wort, but it's impact has not been quantified.