Citrus gall wasp control

Page last updated: Friday, 14 June 2019 - 8:19am

Citrus gall wasp is a pest that affects all citrus species. Citrus tree owners are encouraged to implement control measures on their property to reduce the threat to the citrus industry in Western Australia and continue to enjoy home-grown citrus fruit.

Citrus gall wasp (Bruchophagus fellis) is an Australian native insect from northern NSW and Queensland and now established in some Perth suburbs.

The spread of citrus gall wasp into orchards and backyard citrus trees is usually the result of the introduction of infested citrus plants and the lack of monitoring of gall development in branches. 

Citrus gall wasps have a limited flying range meaning that infestations within a property occur by the close presence of infested citrus trees, including across the fence of urban properties. Spread over long distances is facilitated by the wind and by movement of infested trees or by untreated infested branches.

What to look for

Enlarged stem indicating citrus gall wasp infestation
New galls become visible from April
  • The wasp produces characteristic woody galls which form around the developing larvae. 
  • New-season galls start to become visible in April and are easy to see by June.
  • The best time to check for and remove galls is during June.
Enlarged galls where new shoots developed
Enlarged galls where new shoots developed
  • Search for forming galls on young, green twigs.
  • Inspect for the presence of galls in all nursery stock and new plants prior to and after planting for at least 12 months.
Citrus gall wasp emergence holes
Citrus gall wasp emergence holes
  • Galls located on older branches can indicate that there have been older infestations (previous year or earlier). The presence of holes within the gall indicates that adults have already emerged.
  • Check for galls on established trees all year round.

Control methods

Cultural practices

  • Prune out branches affected by galls. This is essential for controlling the gall wasp. Prune and remove as many galls as possible by June 30 each year. When pruning newly formed galls in April to June, dry them in the sun afterwards to kill the larvae before disposing of them in your green waste, compost or general rubbish.
  • Treat affected branches before disposal. Wasps can emerge from galls in pruning offcuts if pruned too close to the usual emergence period.
  • Galls removed after June should be shredded and solarised, or burnt and deep buriedSolarise galls by placing them in a well-sealed plastic bag, preferably by double bagging, and sitting the bag in the sun to bake for at least four weeks. Disposing of gall offcuts in normal household waste, a green verge collection or in garden bags will spread the pest to other areas
  • Avoid heavily fertilising trees in winter or spring. Over-fertilising (particularly heavy nitrogen applications) can promote excessive amounts of spring growth that the gall wasp prefers.

Management calendar

Timing of control actions varies with locations. Follow citrus tree development suited to your region.

Citrus gall wasp management calendar

Chemical control

Chemical control in the home garden is problematic. Chemicals registered for gall wasp are only available in commercial quantities for use in commercial-sized orchards.

Always check the APVMA website and follow label instructions, witholding periods and permit conditions.

  • Confidor® Guard (Imidacloprid) and Samurai® (Clothiandin) are systemic soil-applied insecticides registered for the control of citrus gall wasp in commercial orchards. They are applied after flowering and control developing larvae before they form destructive galls.

  • Although petroleum spray oils are used against other citrus insect pests, citrus growers can use them to deter gall wasp adults from laying eggs.

  • NSW trials with calcined kaolin clay (Surround®) show promise to disrupt egg laying and reducing galls. Apply at least twice during spring when wasps emerge.

Natural enemies

The wasps Megastigmus brevivalvus and M. trisulcus insert their eggs directly into the eggs of other wasps where it slowly develops in the host larva, eventually killing it. Research is ongoing to determine their potential establishment as a biocontrol agent in Western Australia.

Report citrus gall wasp

Use the MyPestGuide reporter app or web tool to report citrus gall wasp so we can keep track of its spread. 

 

Contact information

MyPestGuide
1800 084 881
Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080

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