Biology, revised taxonomy and impact on host plants of Ophelimus maskelli, an invasive gall inducer on Eucalyptus spp. in the Mediterranean area.
O. maskelli, an invasive species in the Mediterranean area that occurs naturally on E. camaldulensis at Wagga Wagga in New South Wales, Australia, was studied in Israel on the same host plant. The most distinctive characteristic of O. maskelli compared with other congeners is the presence of only a single seta on the submarginal vein. O. maskelli tended to oviposit in developed, immature leaves, and preferred to oviposit on an area of the leaf blade near the petiole. The female laid an average of 109 eggs when maintained on water alone. The egg-laying distribution tended towards aggregation, and the same tendency was also observed within and among trees. The wasp preferred to attack the lower canopy. The gall diameter ranged from 1.2 to 0.9 mm, and gall density varied from 11.5 to 36.0 galls cm-2. The typical colour of the gall appeared as soon as the third instar larva developed. Galls on shaded leaves remained green or greenish-yellow, whereas those that were exposed to the sun were reddish. O. maskelli produced 3e generations per year in Israel. High flight occurred among the spring generations, starting in early March. The wasps were attracted to green sticky plates much more than to yellowish green, pink, reddish or purple plates. Heavy galling by O. maskelli resulted in premature shedding of leaves soon after the emergence of the wasps. Among the 84 Eucalyptus species tested, the following 14 species were found to be suitable hosts: E. botryoides, E. bridgesiana, E. camaldulensis, E. cinerea, E. globulus, E. grandis, E. gunnii, E. nicholii, E. pulverulenta, E. robusta, E. rudis, E. saligna, E. tereticornis and E. viminalis. The morphological and development characters that can clearly distinguish O. maskelli from Ophelimus eucalypti, the effect of crossing between Eucalyptus species on the development possibilities of the wasps, the effect of the food on adult survival, the competition between the eulophid gall maker Leptocybe invasa and O. maskelli, the heavy damage inflicted on Eucalyptus, and health problems and nuisance to people caused by the wasp near heavily infested trees during the mass emergence of adults are discussed.