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• Issue 87 »
• Autumn Activities

Autumn Activities

Tradescantia showing symptoms of infection by the yellow leaf spot fungus at Waingaro. Image: Ben Wolf

There are a few things you might want to fit in before winter sets in. We would be very interested to hear about what you find.

Gall-forming agents

Early autumn is the best time to check many gall-forming agents.

• Check broom gall mite (Aceria genistae) sites for signs of galling. Very heavy galling, leading to the death of bushes, has already been observed at some sites. Harvesting of galls is best undertaken from late spring to early summer, when predatory mites are less abundant.
• Check hieracium sites, and if you find large numbers of stolons galled by the hieracium gall wasp (Aulacidea subterminalis) you could harvest mature galls and release them at new sites. Look also for the range of deformities caused by the hieracium gall midge (Macrolabis pilosellae), but note that this agent is best redistributed by moving whole plants in the spring.
• Check nodding and Scotch thistle sites for gall flies (Urophora solstitialis and U. stylata). Look for fluffy or odd-looking flowerheads that feel lumpy and hard when squeezed. Collect infested flowerheads and put them in an onion- or wire-mesh bag. At new release sites hang the bags on fences, and over winter the galls will rot down, allowing adult flies to emerge in the spring.
• Check Californian thistle gall fly (Urophora cardui) release sites for swollen deformities on the plants. Once these galls have browned off they can be harvested and moved to new sites (where grazing animals will not be an issue), using the same technique as above.
• Although it is early days, it might be worth checking release sites this summer to look for swellings on the stems caused by the giant reed gall wasps (Tetramesa romana). These look like small corn cobs on large, vigorous stems, or like broadened deformed shoot tips when side shoots are attacked. It will be too soon to consider harvesting and redistribution if you do see evidence of the gall wasp establishing.

Japanese honeysuckle white admiral (Limenitis glorifica)

• Look for the adult butterflies, for the pale yellow eggs laid singly on the upper and lower surfaces of the leaves, and for the caterpillars. When small, the caterpillars are brown and found at the tips of leaves, where they construct pontoon-like extensions to the mid-rib. As they grow, the caterpillars turn green, with spiky, brown, horn-like protrusions.
• Unless you find lots of caterpillars, don’t consider harvesting and redistribution activities: unless it is very early autumn this would be better left until the following spring.

Privet lace bug (Leptoypha hospita)

• Examine the undersides of leaves for the adults and nymphs, especially leaves showing signs of bleaching.
• If large numbers are found, cut infested leaf material and put it in chilly bin or large paper rubbish bag, and tie or wedge this material into Chinese privet at new sites. Aim to shift at least 1,000 individuals to each new site.

Tradescantia leaf, stem and tip beetles (Neolema ogloblini, Lema basicostata, N. abbreviata)

• Look for feeding damage and adults. For the leaf and tip beetles look for the external-feeding larvae which have a distinctive protective covering over their backs.
• If you find them in good numbers, aim to collect and shift 50–100 beetles using a suction device or a small net. For stem beetles it might be easier to harvest infested material and wedge this into tradescantia at new sites (but make sure you have an exemption from MPI that allows you to do this).

Tradescantia yellow leaf spot (Kordyana brasiliense)

• Although the fungus was only released last autumn, promising signs of likely establishment have been seen at some sites already, with typical symptoms visible only a few months after the release. Look for the distinctive yellow spots on the upper surfaces of the leaves, with corresponding white spots underneath, especially after wet, humid weather. Feel free to take a photo to send to us for confirmation if you are unsure, as occasionally other pathogens do damage tradescantia leaves.
• The fungus is likely to disperse readily via spores on air currents. If human-assisted distribution is needed in the future, you will need to have permission from MPI to propagate and transport tradescantia plants. These plants can then be put out at sites where the fungus is present until they show signs of infection, and then planted out at new sites.

Tutsan moth (Lathronympha strigana)

• Although the moths were only released last autumn, if you can’t wait, look for the small orange adults flying about flowering tutsan plants. They have a similar look and corkscrew flight pattern to the gorse pod moth (Cydia succedana). Look also for fruits infested with the larvae.
• It is too soon to consider harvesting and redistribution if you do find the moths.

Woolly nightshade lace bug (Gargaphia decoris)

• Check release sites by examining the undersides of leaves for the adults and nymphs, especially leaves showing signs of bleaching or black spotting around the margins.
• It is probably best to leave any harvesting until spring.

National Assessment Protocol

For those taking part in the National Assessment Protocol, autumn is the appropriate time to check for establishment and/or assess population damage levels for the species listed in the table below. You can find out more information about the protocol and instructions for each agent at: www.landcareresearch.co.nz/publications/books/biocontrol-of-weeds-book

Contact:
Lynley Hayes (hayesl@landcareresearch.co.nz)