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• Issue 82 »
• Summer Activities

Summer Activities

Tutsan moth larva inside fruit.

Summer is a busy time for many biocontrol agents so you might need to schedule the following activities.

Broom gall mites (Aceria genistae)

• Check for galls, which look like deformed lumps and range in size from 5 to 30 mm across. 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. Aim to shift at least 50 galls to each site and tie them on to plants so the tiny mites can shift across.

Broom leaf beetles (Gonioctena olivacea)

• Look for beetles by beating plants over a tray. The adults are 2–5 mm long and goldish-brown (females) through to orangey-red (males), with stripes on their backs. Look also for greyish-brown larvae, which may also be seen feeding on leaves and shoot tips.
• If you find beetles in good numbers, aim to shift at least 300 to sites that are not yet infested with gall mites.

Darwin’s barberry weevil (Berberidicola exaratus)

• Although it is early days for checking release sites, you could beat plants in late summer to look for new adults. They are blackish-brown and 3−4 mm long.
• It’s too soon to consider harvesting and redistribution.

Green thistle beetles (Cassida rubiginosa)

• Look for adult beetles, which are 6–7.5 mm long and green, so they camouflage quite well. Both the adults and the larvae make windows in the leaves. Larvae have a protective covering of old moulted skins and excrement. You may also see brownish clusters of eggs on the undersides of leaves.
• If you find good numbers, use a garden leaf vacuum machine to shift at least 100 adults to new sites. Be careful to separate the beetles from other material collected, which may include pasture pests.

Privet lace bug (Leptoypha hospita)

• Check for establishment by examining 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 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 skeletonised by larvae grazing off the green tissue.
• 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: 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 MPI that allows you to do this).

Tradescantia tip beetle (Neolema abbreviata)

• Look for the adults, which are mostly black with yellow 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.
• If you find them in good numbers aim to collect and shift 50–100 beetles using a suction device or a small net.
  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

National Assessment Protocol

For those taking part in the National Assessment Protocol, summer 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

Send any reports of interesting, new or unusual sightings to Lynley Hayes (hayesl@landcareresearch.co.nz, Ph 03 321 9694).