What's New in Biological Control of Weeds?, Issue 61

August 2012

In this issue

Map showing the potential distribution of St John’s Wort in the South Island.

How Cost-Effective Is Successful Weed Biocontrol in New Zealand?

A recent economic analysis by Simon Harris (Harris Consulting) and Simon Fowler looked at whether it has been cost-effective to release biocontrol agents against weeds in New Zealand.

The Darwin’s barberry seed-feeding weevil.

New Agent Approvals

The Environmental Protection Authority (EPA) has approved an application to release the lantana leaf rust (Prospodium tuberculatum) and the lantana blister rust (Puccinia lantanae) in New Zealand.

Tradescantia stem showing typical damage caused by a stem beetle larva.

Changes to Pages

If you are making an effort to keep your copy of The Biological Control of Weeds Book – Te Whakapau Taru up to date you need to go online and download some new and revised pages.

Male broom leaf beetle (<em>Gonioctena olivacea</em>).

Biocontrol Agents Released in 2011/12

Seven species have been released this year at 138 sites around New Zealand.

Who Is Eating Our Agents?

When new agents establish themselves on host plants, they enter existing food webs and their effectiveness can be influenced by the presence of other species, either native or exotic. Interactions can occur between different insect species or can involve larger predators, and because they are not always obvious, they have not been well studied.

The new psyllid (<em>Acizzia solanicola</em>) found recently in Auckland.

Never a Dull Moment with Woolly Nightshade!

A number of additional species have been found attacking woolly nightshade (Solanum mauritianum) in New Zealand since we undertook comprehensive surveys of its natural enemies in 2000/01.

Figure showing the placement of NZ and Hawaiian kahili ginger (Hedychium gardnerianum x coronarium?) compared to kahili ginger (H.gardnerianum) from India, and placement of yellow ginger (H. flavescens) and white ginger (H. coronarium) from NZ and India. Note that the NZ kahili ginger sample has four sets of chromosomes (tetraploid), and we suspect Hawaiian material will be the same when tested, whereas the other species only have two sets (diploid).

Secrets of Wild Ginger Revealed

The two problematic species in New Zealand are known as kahili ginger (Hedychium gardnerianum) and yellow ginger (H. fl avescens).

<em>Alternanthera nahui</em>, no longer a major impediment to developing biocontrol for alligator weed.

Key Hurdle Cleared for Alligator Weed Project

The only aquatic weed we have attempted to biocontrol in New Zealand is alligator weed (Alternanthera philoxeroides).

Lizzie surveying tutsan in the North Island.

International Effort Underway against Tutsan

Tutsan (Hypericum androsaemum) is an invasive weed that originates from Europe and has become a significant pest in the North Island.

Tip necrosis symptoms on Chinese privet.

Spotlight Finally on Privet

Privet (Ligustrum spp.) has a large native range, across Europe to eastern Asia and south to Queensland, Australia. There are approximately 40 species, but only four have been introduced to New Zealand: tree privet (L. lucidum), Chinese privet (L. sinense), common privet (L. vulgare), and Californian privet (L. ovalifolium).