Farm Forestry New Zealand
PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
Ophelimus, eulophid (chalcidoid) wasps on Eucalyptus spp.
Scion is the leading provider of forest-related knowledge in New Zealand
Formerly known as the Forest Research Institute, Scion has been a leader in research relating to forest health for over 50 years. The Rotorua-based Crown Research Institute continues to provide science that will protect all forests from damage caused by insect pests, pathogens and weeds. The information presented below arises from these research activities.
UPDATE ON THE EULOPHID (HYMENOPTERAN) GALL-FORMERS ON EUCALYPTUS SPP.
From Forest Health News 81, January 1999.
Many thanks to the MAF forest health advisers and others who have sent in eucalypt foliage containing leaf galls over the past 9 months. Many eulophid (chalcidoid) wasps have now been reared from these galls and tentative hypotheses are being formulated. Our current knowledge of gall wasps affecting eucalypts in New Zealand is as follows.
The old Rhicnopeltella, now Ophelimus eucalypti (Gahan), is distributed throughout New Zealand. Insects morphologically indistinguishable from 0. eucalypti , have been reared from blue gums such as E. globulus, E. nitens, and E. viminalis. It is still uncertain as to whether the specimens from the midrib and branch galls, and the small sandpaper type galls on juvenile leaves of these hosts are all the same species. Ophelimus sp. b is distributed throughout New Zealand on E. saligna and E. botryoides . Insects reared from E. grandis galls are morphologically identical with Ophelimus sp. b from E. saligna. Individually handled females have been observed to oviposit their eggs in both E. grandis and E. saligna leaves in the laboratory and in the field, suggesting both hosts are equally acceptable. However, it may be that these hosts are not equally suitable for Ophelimus larval development within the leaf gall. Eucalyptus grandis leaves which have been subjected to heavy ovipositing tend to be shed earlier and often the only galls that develop are very small, giving the galled leaf a quite different appearance to those of galled E. saligna and E. botryoides . The adults that emerge from these small galls are almost always males. This may suggest that E. grandis leaves often do not support female development (with their probable greater nutritional requirements) through to pupation and emergence. This hypothesis is currently under investigation. This survey has also resulted in the recognition of at least three more species of Eulophidae. The most abundant species, a distinct yellow and black Aprostrocetus species has emerged from stem and leaf galls of (Northland to Wellington), from blue gum sandpaper galls (Marlborough), from E. globulus, E. kitsoniana galls (Wellington), from E. grandis leaf galls (Wellington), and E. saligna and E. botryoides leaf galls (throughout the North Island). This distribution combined with the known biology of other Aprostrocetus species strongly suggests that it is parasitic on all gall-forming Ophelimus species found in New Zealand. Another eulophid, a metallic looking Chrysonotomyia species has been collected from leaf galls of E. grandis, E. saligna and E botryoides (throughout North Island). It is probable that this species is also a parasitoid of Ophelimus sp. b. We would like to collect further specimens from eucalypt galls from the South Island, and more from outlying areas of the North Island such as Taranaki, Coromandel, Gisborne, and Northland. Research plans for the next year are to ascertain the parasitism status of these other eulophid species, to describe the gall induction mechanism of Ophelimus sp. b, and to use morphological and molecular techniques to delimit the species of Ophelimus present in New Zealand.
Toni Withers, Forest Research
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(Scion is the trading name of the New Zealand Forest Research Institute Limited.)
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