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• Issue 79 »
• Autumn Activities

Autumn Activities

Drawing by Susan Marks.

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 though, 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.
• At nodding and Scotch thistle gall fly (Urophora solstitialis and U. stylata) release sites 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.
• At Californian thistle gall fly (Urophora cardui) release sites look 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.

Privet lace bug (Leptoypha hospita)

• Although it is early days, it might be worth checking release sites. Examine the undersides of leaves for the adults and nymphs, especially leaves showing signs of bleaching.
• It is likely to be too soon for any harvesting to begin.

Tradescantia leaf beetle (Neolema ogloblini)

• Look for the shiny, metallic-bronze adults or the larvae, which have a distinctive protective covering over their backs. Also look for notches in the edges of leaves caused by adult feeding, or leaves that have been windowed by larvae grazing off the green tissue.
• The beetles can be harvested if you find them in good numbers. Aim to collect and shift 50–100 beetles using a suction device or a small net.

Tradescantia stem beetle (Lema basicostata)

• The black knobbly adults can be difficult to see, so look for their feeding damage, which consists of elongated windows in the upper surfaces of leaves, or sometimes whole leaves consumed. Also look for stems showing signs of larval attack: they will be brown, shrivelled or dead-looking.
• If you can find widespread damage, you can begin harvesting. If it proves too difficult to collect 50–100 adults with a suction device, remove a quantity of the damaged material and put it in a wool pack or on a tarpaulin and wedge this into tradescantia at new sites (but make sure you have an exemption from the Ministry for Primary Industries that allows you to do this).

Tradescantia tip beetle (Neolema abbreviata)

• Look for the adults, which are mostly black with yellow and black wing cases, and their feeding damage, which like stem beetle damage consists of elongated windows in the leaves. Larvae will be difficult to see inside the tips, but brown frass may be visible. When tips are in short supply, the slug-like larvae feed externally on the leaves.
• The beetles can be harvested if you find them in good numbers. Aim to collect and shift 50–100 beetles using a suction device or a small net.

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, spring 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