Weed Biocontrol Issue 81
In this issue
![Tussock thumb.jpg Dying nassella tussock in Argentina affected by crown rot fungus. <em>Photo credit: Bill Pettit</em>](https://oldwww.landcareresearch.co.nz/__data/assets/image/0003/148143/varieties/thumb200.jpg)
Still Tussling with Tussocks
Many New Zealanders would be very happy if we could successfully biocontrol two closely related weedy grasses: Chilean needle grass (Nassella neesiana) and nassella tussock (Nassella trichotoma).
![Alligator weed thumb.jpg Alligator weed beginning to show severe moth damage in 1991.](https://oldwww.landcareresearch.co.nz/__data/assets/image/0008/148139/varieties/thumb200.jpg)
Alligator Weed: A Financial Snapshot
Alligator weed (Alternanthera philoxeroides) is a tough plant to control. Herbicides can be used to some extent, but the structure of this plant, with its many nodes, means translocation can be poor.
![Wild ginger thumb.jpg Ginger infesting plantation forestry in Northland. <em>Photo credit: Bill Pettit.</em>](https://oldwww.landcareresearch.co.nz/__data/assets/image/0007/148147/varieties/thumb200.jpg)
Turning up the Heat on Ginger
Molecular studies suggest that the most invasive form of wild ginger in Northland is a hybrid between kahili ginger (Hedychium gardnerianum) and most likely white ginger (H. coronarium), both of which originate from India.
![wild daisy.jpg Mexican daisy. <em>Photo credit: Auckland Council.</em>](https://oldwww.landcareresearch.co.nz/__data/assets/image/0005/148145/varieties/thumb200.jpg)
Biocontrol for Mexican Daisy?
Mexican daisy (Erigeron karvinskianis), an emerging environmental weed in New Zealand, was introduced as an ornamental plant in the 1940s.
![Alder.jpg Alder with dense native understory. <em>Photo credit: Kate McAlpine.</em>](https://oldwww.landcareresearch.co.nz/__data/assets/image/0007/148138/varieties/thumb200.jpg)
Beating Weeds with Science
The idea that leaving the more than 50 species of woody weeds in the environment until they are outcompeted by native species has advantages.
![Barberry weevil.jpg Fruits infested with Darwin’s barberry weevil.](https://oldwww.landcareresearch.co.nz/__data/assets/image/0019/148141/varieties/thumb200.jpg)
Spring Activities
Most biocontrol agents become active during spring, making it a busy time of year to check release sites and move agents around.
![broom_culverden_200.jpg Broom](https://oldwww.landcareresearch.co.nz/__data/assets/image/0020/30935/varieties/thumb200.jpg)
Who’s Who
Complete list of biological control agents in use in New Zealand.
![Japanese_Honeysuckle_200.jpg Japanese Honeysuckle](https://oldwww.landcareresearch.co.nz/__data/assets/image/0004/148252/varieties/thumb200.jpg)
Further reading
Recent publications relating to the biological control of weeds
![biocontrol_weeds_cover-150.jpg](https://oldwww.landcareresearch.co.nz/__data/assets/image/0010/124885/varieties/thumb200.jpg)
Changes to pages
If you are keeping your copy of The Biological Control of Weeds Book up to date you might like to download the following new or amended pages.