Eurytoma Citrus Gall
Background
In March 2007, samples of citrus rootstock twigs with unusual insect damage were collected from a property in the Central Burnett region of Queensland.
A single wasp reared from the infested twigs resembled the native citrus gall wasp (CGW, Bruchophagus fellis). However, the damage, symptoms and larvae were sufficiently different from CGW to raise concerns that this may be an exotic pest or a native pest not previously associated with citrus.
Wasps reared from infested twigs were identified to be from the genus Eurytoma, but the species could not be determined.
Damage has been noted on twigs, thorns, soft terminal growth and the bases of midribs and petioles.
It is not known if the wasp attacks citrus varieties commonly grown in Victoria.
Symptoms and damage
Affected twigs have soft, raised, spherical or irregular swellings, with numerous small, white larvae inside. Affected thorns are shortened, swollen and distorted.
Unlike CGW, Eurytoma galls are not woody, the larvae do not occur in circular cells and it can complete several generations per year.
Emergence holes associated with Eurytoma wasps can be apparent at ~20cm intervals on stems in which several generations of the wasp have been completed.
Heavy infestation of soft terminal tissue causes cessation of growth, poor graft performance and production of regrowth shoots below damaged areas; the worst affected twigs break off just below the growing point.
You can help to establish the distribution of the wasp by reporting damage or symptoms on citrus similar to that shown above.
Call the EXOTIC PLANT PEST HOTLINE 1800 084 881
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