Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Autumn Activities

Heavily galled broom at a release site in Hanmer Springs. Image - Rob Simons

Heavily galled broom at a release site in Hanmer Springs. Image - Rob Simons

There are a few things you might want to fit in before the wind-down towards winter. We would be very interested to hear about what you find.

Broom gall mite (Aceria genistae)

  • Check release sites for galls, which look like deformed lumps and range in size from 5 to 30 mm across. Very heavy galling has already been observed at some sites (see photo).
  • Harvesting of galls is best left until spring when predatory mites are less abundant.

Gall-forming agents

  • Early autumn is the best time to check release sites for many gall-forming agents. If you find large numbers of galls caused by the mist flower gall fly (Procecidochares alani) and hieracium gall wasp (Aulacidea subterminalis), you could harvest mature ones and release them at new sites.
  • Do not collect galls caused by the hieracium gall midge (Macrolabis pilosellae) as 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 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.

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 fly 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. To see damage you may need to look at the older leaves lower down in the canopy.
  • 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 difficult to spot. Look for stems showing signs of necrosis or collapse and brown frass.
  • It may be possible to begin harvesting and redistribution at some sites soon, but spring would be the best time to do this.

Tradescantia tip beetle (Neolema abbreviata)

  • Most release sites are still quite new but there is no harm in looking. The adults are mostly black with yellow wing cases, but like the other tradescantia beetles tend to drop when disturbed. Larvae will also be difficult 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)

  • Autumn last year was when the first substantial, damaging outbreaks of the lace bug were noticed in the Bay of Plenty. Check release sites by examining the undersides of leaves for the adults and nymphs, especially of leaves showing signs of bleaching or black spotting around the margins.
  • It is probably best to leave any harvesting of lace bugs until spring.