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• Issue 86 »
• Summer activities

Summer activities

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 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 move 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.
• The beetles can be harvested if you find them in good numbers. Aim to move at least 100 beetles 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, which are small (3−4 mm long) and blackish. Also examine the fruits for signs of puncturing.
• Since establishment is not yet confirmed, it will be too soon to consider harvesting and redistribution if you do find the weevils.

Giant reed gall wasp (Tetramesa romana)

• Again, although it is early days it might be worth checking release sites this summer to look for swellings on the stems caused by the gall wasps. 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.

Green thistle beetles (Cassida rubiginosa)

• December is often the time when green thistle beetle activity is at its peak. Look for adult beetles, which are 6–7.5 mm long and green, which means 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. Please let us know if you discover an outbreak of these beetles.

Japanese honeysuckle white admiral (Limenitis glorifica)

• Look for the adult butterflies at release sites over summer. Look also for 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.

Privet lace bug (Leptoypha hospita)

• Although it is early days for privet lace bug, signs of their presence seem to be obvious quite soon following releases, so it would definitely be worth checking the older release sites to confirm establishment. 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 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 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 for 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.

Tradescantia yellow leaf spot (Kordyana brasiliense)

• Although the fungus was only released this past autumn, promising signs of likely establishment seen only a few months afterwards make it worth checking release sites this spring. Look for the distinctive yellow spots on the upper surface 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 to propagate and transport tradescantia plants from MPI. 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.

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