Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Spring Activities

Bridal creeper rust.

Bridal creeper rust.

Most biocontrol agents become active during spring, making it a busy time of year to check release sites and move agents around.

Boneseed leafroller (Tortrix s.l. sp. “chrysanthemoides”)

  • Check release sites for feeding shelters made by caterpillars webbing together leaves at the tips of stems. Also look for “windows” in the leaves and sprinkles of black frass. Small caterpillars are olive-green in colour and become darker, with two parallel rows of white spots as they mature.
  • Caterpillars can be harvested if you find them in good numbers. Cut off infested boneseed tips and wedge them into plants at new sites. Aim to shift at least 500 caterpillars to sites where scale insects and invasive ants are not known to be present.

Bridal creeper rust (Puccinia myrsiphylli)

  • Check bridal creeper infestations for bridal creeper rust, particularly sites where it has not been found before. Plants infected by the rust have yellow and black pustules on the undersides of leaves and on stems and berries. They may look defoliated and sickly.
  • It is unlikely that you will need to redistribute bridal creeper rust because it is so widespread, but if you do, detailed instructions are available in the factsheet:Bridal creeper rust fungus.

Broom gall mites (Aceria genistae)

  • Check release sites for galls, which look like deformed lumps and range in size from 5 to 30 mm across. Occasionally galls can be found on broom that are not made by the gall mite, but these are much less dense. Also you may see galls on native broom that are caused by native gall mites. We are happy to help confirm the identity of any galls you find.
  • If galls are present in good numbers, late spring – early summer is the best time to undertake harvesting and redistribution. Because the mites are showing much promise but are expected to disperse quite slowly, it will be important for all regions with a major broom problem to plan a comprehensive redistribution programme. Aim to shift at least 50 galls to each site and tie them onto plants so the tiny mites can shift across.

Broom leaf beetles (Gonioctena olivacea)

  • Check release sites by beating plants over a tray. Look for the adults, which 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 that may also be seen feeding on leaves and shoot tips.
  • It is probably still a bit soon to begin harvesting and redistribution.

Broom shoot moth (Agonopterix assimilella)

  • Late spring is the best time to check release sites. Look for the caterpillars’ feeding shelters made by webbing twigs together. Small caterpillars are dark reddish-brown and turn dark green as they get older. We have only found reasonable evidence of establishment at one site in Southland to date, so we will be interested to hear if you find any sign of the caterpillars.
  • We would not expect you to be able to begin harvesting and redistribution just yet.

Green thistle beetles (Cassida rubiginosa)

  • Check release sites for adult beetles, which emerge on warm days towards the end of winter and feed on new thistle leaves making round window holes. The adults are 6–7.5 mm long and green, but are quite well camoufl aged against the leaf. The larvae also make windows in the leaves. They have a protective covering of old moulted skins and excrement. You may also see brownish clusters of eggs on the underside of leaves.
  • It should be possible to begin harvesting and redistribution at some sites. Use a garden-leaf vacuum machine and aim to shift at least 50 adults from spring throughout summer and into autumn. Be careful to separate the beetles from other material collected, which may include pasture pests.

Ragwort plume moth (Platyptilia isodactyla)

  • October is the best time to check release sites for caterpillars. Look for plants with wilted or blackened or blemished shoots with holes and an accumulation of debris, frass or silken webbing. Pull back the leaves at the crown of damaged plants to look for large hairy, green larvae and pupae.
  • Also check where the leaves join bolting stems for holes and frass. Don’t get confused by larvae of the blue stem borer (Patagoniodes farinaria), which look similar to plume moth larvae until they develop their distinctive bluish colouration.
  • If the moth is present in good numbers, the best time to shift it around is in late spring. Dig up damaged plants, roots and all. Pupae may be in the surrounding soil so retain as much as possible. Shift at least 50–100 plants, but the more the better. Place one or two infested plants beside a healthy ragwort plant so any caterpillars can crawl across.

Tradescantia leaf beetle (Neolema ogloblini)

  • Check release sites, especially the older ones. 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. You may see the dark metallic bronze adults, but they tend to drop or fl y away when disturbed. It may be easier to spot the larvae, which have a distinctive protective covering over their backs. The white, star-shaped pupal cocoons may be visible on damaged foliage.
  • We would not expect you to find enough beetles to be able to begin harvesting and redistribution just yet.

Tradescantia stem beetle (Lema basicostata)

  • Check release sites, especially the older ones. The black knobbly adults also tend to drop when disturbed, but look for their feeding damage, which consists of elongated windows in the upper surfaces of leaves or sometimes whole leaves consumed. The larvae inside the stems will also be diffi cult to spot. Look for stems showing signs of necrosis or collapse and brown frass.
  • We would not expect you to find enough beetles to be able to begin harvesting and redistribution just yet.

Tradescantia tip beetle (Neolema abbreviata)

  • Releases only began in 2013, but there is no harm in checking release sites. The adults are mostly black with yellow wing cases, but like the other tradescantia beetles tend to drop when disturbed. Larvae will also be diffi cult to see when they are feeding inside the tips, but brown frass may be visible. When tips are in short supply, the slug-like larvae feed externally on the leaves.
  • We would not expect you to find enough beetles to be able to begin harvesting and redistribution just yet.

Woolly nightshade lace bug (Gargaphia decoris)

  • Once the weather warms up look on the undersides of leaves at release sites for the adults and nymphs, especially on leaves showing signs of bleaching or black spotting around the margins.
  • We expect the lace bugs might also be slow to disperse, so if good numbers are present, it would be worth collecting some to release in other areas. As per the story in this newsletter there is now some evidence that the lace bugs do best in partial shade, it would be best to target sites where woolly nightshade is partially shaded, for any redistribution efforts. Always wear gloves when handling woolly nightshade foliage to avoid any health issues. Cut leaf material that is infested with adults and/or nymphs and wedge or tie this material firmly into new woolly nightshade plants so the lace bugs can move across. We recommend that you shift at least 1000 individuals to each new site at any time during the warmer months.

Other agents

You might also need to check or distribute the following this spring (for further details see the Biocontrol of Weeds Book):

  • Broom psyllid (Arytainilla spartiophila)
  • Broom seed beetle (Bruchidius villosus)
  • Gorse soft shoot moth (Agonopterix umbellana)
  • Gorse thrips (Sericothrips staphylinus)
  • Gorse colonial hard shoot moth (Pempelia genistella
  • Ragwort crown-boring moth (Cochylis atricapitana)

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