Blue gum chalcid

Blue gum chalcid
Leptocybe invasa
Leaf gall forming

Leptocybe invasa is a gall-forming wasp of various Eucalyptus species. Gall-formation occurs on the leaves, petioles and stems of the young growing plant part.  Area of gall-formation (i.e. leaves, petiole, stem) on the host is dependent on the host species. Large numbers of the wasp result in a high frequency of oviposition which may results in stunted growth or even tree death. Seedlings, coppice growth and young developing leaves are at highest risk (Mendel et al. 2004).

The wasp is 1.1 – 1.4 mm in size with a brown head and body which has a blue to green metallic shine. The head is weak with a distinct groove between the head and thorax. The fore coxa are yellow and the middle and hind coxae the same colour as the insect body. The wings are translucent with a “smoky” patch  (Mendel et al. 2004).

Leptocybe invasa has a thelytokous reproductive system, where all offspring are female and are produced parthenogenetically. Male specimens are absent or very rare. Oviposition occurrs on young plant tissue of the stem, petiole and leaves as early as 1-2 weeks after bud break out. Eggs are laid in a line on the young plant tissue and are often visible as minute black scarring or dots, especially along the leaf midrib. Average developmental time from oviposition to wasp emergence is approximately 4.5 months.

Wasps are most active in the early morning and late afternoon and may survive to 6 days if provided with sources of honey and water. Oviposition occurs in the summer months with a single female being able to lay up 250 eggs.

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Galls on petioles
Adult female
Oviposition marks/scars along midrib of leaf
Galls on midrib of leaves
Adult male
Larvae inside cavities within gall