Forest & Bird Manawatū - 2019 Monthly Meeting

Talk: “Restoring balance using biological control"
Speaker: Craig Davey, Horizons Environment Programme Coordinator, Biosecurity in Plants

The talk will focus on the biological control options for old man’s beard with other examples of biological control success and tribulations.

Restoring the balance using biological control - As a nation we learnt too slowly just what is at stake from the slow change to our natural heritage brought by introduced vegetation. The changes, though slower when compared to the effect on fauna by predators, are as far reaching and, in some cases, as irreversible as a species extinction.

Due to morphological traits, an ability to out compete, as well as a lack of predation from insects or diseases in their home range, allows weeds to remove habitats and have relatively free reign once established. It is the unfettered ability to colonise and then transform that is the secret to weed invasion.

The use of biological control to limit and control plants is a technique in use for over one hundred years. Many of our worst weeds are benign in their country of origin. As an example Tradescantia fluminensis in Brazil has a biomass per metre square of no more than 200g, where in New Zealand it can be found up to 1000g.

Currently New Zealand has imported four agents; one rust and three insects, in an attempt to reduce the biomass found in New Zealand populations to allow native or other seedlings light and the ability to co-exist, grow through and eventually join the canopy.

All welcome. Gold coin donation appreciated.