Weeds, pests & a new hero

I spent last weekend in beautiful Wanaka at the Aspiring Conversations festival. I was very excited to hear Tim Flannery (scientist and founder of Australia’s independent Climate Council), climate researcher Suzi Kerr and science communicator Veronika Meduna talk about climate change.

Relevant to gardeners and farmers was that in New Zealand we can expect more dry days in winter and spring although the rain that does fall will do so in heavier and more intense bursts which will mean more flooding.

More insect pests will make it through milder winters, meaning populations will not make a slow gain as spring continues but already be strong and in good numbers at the start of spring. As someone who doesn’t spray, this was worrying. Personal experience tells me that a cold snap in winter really knocks back pests that would otherwise over-winter in good numbers. Balance will be lost.

Another comment was that the planet doesn’t need us to save it – in fact, it doesn’t need us at all!


The fruit of Cornus capitata are, apparently, edible, although can be bitter. The birds were certainly leaving them alone. Photo: Sandra Simpson

I stayed in the Wanaka Hotel, which featured a Pye radio fitted to the wall above the bed (I didn’t try it). Saw an interesting tree from my balcony so nipped down to photograph it and on the morning I was leaving was lucky enough to meet the knowledgeable owner(?) who this weekend is at the Dendrology NZ conference at Eastwoodhill Arboretum.

Cornus capitata, he said, strawberry tree. Although native to the Himalayas, India and China, the Waiere Nursery says it tolerates only light frosts, while the Weedbusters website lists it as a pest, although doesn’t stipulate whether that is New Zealand wide.

The fruit, which is what I spotted, forms at the centre of a ‘flower’ that is in reality four pale petal-shaped bracts. The Missouri Botanical Garden website notes that it is not reliably evergreen and in colder areas may drop foliage.

A weed that’s been making the news – and sounds rather alarming – is velvetleaf. It has been found in fooder beet crops in both the North and South Islands and the Ministry of Primary Industries (MPI) is asking for help.

Search and destroy activities have been conducted on more than 600 properties since March when velvetleaf was discovered in several regions with the weed found on 215 properties in 11 regions to date.

Dr Veronica Herrera, director of investigations, diagnostics and response, says MPI is continuing to investigate how contaminated fodder beet seed entered New Zealand and has beefed up border inspections.

“MPI has already established that some lines of fodder beet seed grown in Italy and pelletised in Denmark were contaminated with velvetleaf. These lines have been banned from entry into New Zealand.” MPI’s velvetleaf hotline is 0800 80 99 66.

I know some people don’t take our biosecurity very seriously – and it can be jolly annoying not to be able to buy bulbs in Schiphol Airport or to leave flower seed or a cutting in a foreign garden – but this is why we should. Farming, forestry, horticulture and floriculture are how some families earn their living so every incursion is a threat to someone being able to put bread on the table for their kids or a roof over their heads.

Meanwhile, Honshu white admiral butterflies (Limenitis glorifica) have been released to combat the pest plant Japanese honeysuckle (Lonicera japonica). “The big issue with Japanese honeysuckle is that because it’s a climber it’s really hard to kill with herbicides without killing the thing it’s climbing on at the same time. Biocontrol is seen as a friendlier way to control it,” says Landcare Research scientist Quentin Paynter.

And with nothing to predate on it – until now – the plant has became a major problem in some areas.

The white admiral butterfly was chosen after field surveys in Japan indicated that it is found in a variety of habitats from hot lowland sites to cool mountain areas, suggesting it should be able to adapt to New Zealand.

The release of the first butterflies in 2013 in Wellington and the next year in Waikato was a milestone after numerous setbacks including disruption to the research programme because of the Canterbury earthquakes and the 2011 tsunami in Japan.

Japanese honeysuckle was introduced to New Zealand as a garden plant but has become firmly established in bush environments – and grows up to 15m a year in ideal conditions. White admiral caterpillars feed exclusively on Japanese honeysuckle.

The latest newsletter from Te Puna Quarry Park reveals that they’re trying to establish a white admiral colony there. It appears they’ve succeeded in establishing a yellow admiral population, but no luck yet with the red admirals.