Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Spring Activities

Early signs of tradescantia yellow leaf spot infections in the field.

Early signs of tradescantia yellow leaf spot infections in the field.

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

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 shift at least 100 beetles to sites that are not yet infested with gall mites.

Broom shoot moth (Agonopterix assimilella)

  • Late spring is the best time to check release sites, so 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 are unsure if this moth has managed to successfully establish in New Zealand, 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.

Darwin’s barberry weevil (Berberidicola exaratus)

  • Although it is early days for checking release sites, later in the spring it might be worth beating some plants to see if any of the small (3−4 mm long), blackish adults can be found. 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

  • Again, although it is early days it might be worth checking release sites this spring 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.

Japanese honeysuckle white admiral

  • Look for the adult butterflies at release sites from late spring. 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.

Lantana blister rust (Puccinia lantanae)

  • Check sites where lantana plants infected with blister rust have been planted out, especially after a period of warm, wet weather. Signs of infection include leaf and stem chlorosis (yellowing), accompanied by large, dark pustules on the undersides of leaves and on the stems. Stunting, defoliation and die-back may also be apparent.
  • Once established, this rust is likely to be readily dispersed by the wind. If redistribution is needed, this will require placing small, potted lantana plants beneath infected ones and then planting these out at new sites once they have become infected. However, to propagate and distribute lantana in this manner, an exemption from the Ministry for Primary Industries (MPI) will be required.

Lantana leaf rust (Prospodium tuberculatum)

  • Check sites where the leaf rust has been released, especially after a period of warm, wet weather. Look for yellowing on the leaves, with corresponding brown pustules and spores, rather like small coffee granules. A hand lens may be needed to see the symptoms during early stages of infection. If the rust is well established, then extensive defoliation may be obvious.
  • Once established, this rust is likely to be readily dispersed by the wind. If redistribution efforts are needed, the best method is to harvest infected leaves, wash them in water to make a spore solution, and then apply this to plants.

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.

Ragwort plume moth (Platyptilia isodactyla)

  • October is the best time to check release sites for caterpillars, so look for plants with wilted, 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 coloration.
  • 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 that any caterpillars can crawl across.

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.

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, again it will be necessary to get 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.

Other agents

You might also need to check or distribute the following this spring:

  • boneseed leafroller (Tortrix s.l. sp. “chrysanthemoides”)
  • broom gall mites (Aceria genistae)
  • gorse colonial hard shoot moth (Pempelia genistella)
  • green thistle beetle(Cassida rubiginosa)
  • tradescantia stem beetle (Lema basicostata)
  • tradescantia tip beetle(Neolema abbreviata).
  • gorse soft shoot moth (Agonopterix ulicetella)
  • gorse thrips (Sericothrips staphylinus)
  • tradescantia leaf beetle (Neolema ogloblini)

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:

Broom Oct–Nov
Leaf beetle (Gonioctena olivacea)
Psyllid (Arytainilla spartiophila)
Shoot moth (Agonopterix assimilella)
Twig miner (Leucoptera spartifoliella)
Lantana Oct–Nov
(or March–May)
Blister rust (Puccinia lantanae)
Leaf rust (Prospodium tuberculatum)
Tradescantia Nov–April
Leaf beetle (Neolema ogloblini)
Stem beetle (Lema basicostata)
Tip beetle (Neolema abbreviata)
Yellow leaf spot fungus (Kordyana brasiliense)

Lynley Hayes –