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This paper describes a series of host-specificity tests carried out to evaluate the safety of eight insects for release in Australia as biological control agents of Onopordum spp. thistles; Larinus latus L., Lixus cardui Ol. and Trichosirocalus briesei Alonso-Zarazaga & Sanchez-Ruiz (Coleoptera: Curculionidae), Tephritis postica Loew and Urophora terebrans Loew (Diptera: Tephritidae), Botanophila spinosa Rondani (Diptera: Anthomyiidae), Tettigometra sulphurea Mulsant & Rey. (Hemiptera: Fulgoroidae) and Eublemma amoena (Hbn.) (Lepidoptera: Noctuidae). Preliminary tests were first carried out against key test plants in the country of origin to determine whether it was worth proceeding with formal testing under quarantine conditions in Australia. In the formal testing procedure, the test plant list was based solely on phylogenetic relationships. The life-stage of each insect tested was selected with respect to its biology and behaviour, e.g. only oviposition was tested for insect species with immobile endoph...

The impact of root-feeding insects attacking the 'biennial' Carduus nutans L. in the southern part of its native European distribution was studied as part of a biological control programme against this weed for Australia. Surveys were conducted from Spain to Greece to parallel previous studies in central Europe and three populations of the weed were monitored in detail over a 2-4-year period in southern France. The damage levels and attack patterns of each insect species were recorded. The most common species damaging the roots and meristems were the weevils Hadroplontus (=Ceutorhynchus) trimaculatus F. and Trichosirocalus horridus Panzer and the syrphid fly Cheilosia corydon Harris (=grossa Fallen). In manipulative experiments, made to assess their impact on the host plant, C. corydon reduced seed production by up to 45%, while the two weevils mainly altered plant architecture. The results are discussed in relation to previous experience of using root feeders for the biological control of C. nutans.

Bembecia chrysidiformis (Esper) [Lep.: Sesiidae] was examined for its natural history and specificity toRumex spp. (Polygonaceae) which are weeds in Australia. Adults of this southern European insect appear in late spring to summer. Eggs are laid on the dried, seed bearing stems of perennialRumex plants. The larvae tunnel inside the root during summer through to the next spring. In nature, the larvae are round inRumex species of the subgeneraRumex andAcetosa. In host-specificity tests with 1st instar larvae, the roots of a number of genera within thePolygonaceae were attacked. Larvae died on a range of plants from other families except inPersea americana Miller(Lauraceae), Helianthemum nummularium (L.) Miller (Cistaceae) andQuercus ilex L. (Fagaceae) where larvae fed on the stems. The insect was judged safe for release in Australia by assessing aspects of its biology, its known host plants, and the lack of reported attack on other plants.

In South Australia, Reseda lutea is abundant, invading pastures and crops on calcareous soils while in its native Mediterranean range it is uncommon in occurrence and is not reported as a weed of cultivated crops. Its invasive behaviour in South Australia may be attributed to vegetative growth of root fragments spread by cultivation, while propagation by seed is of minor importance. Surveys in Spain, Portugal, Morocco, France, Turkey and Israel indicated that agronomic differences, particularly depth of cultivation and seeding rates of cereals may explain why it is not a crop weed in these countries. Another difference is that plants in the region of origin have an associated fauna not present in Australia. These potential biological control agents include a root-boring weevil, Baris picicornis, flower- and seed-feeding urodontids, Bruchela suturalis and B. rufipes, and a leaf spot pathogen,Cercospora resedae. Baris picicornis was introduced from France and Turkey, under quarantine, to Australia but laboratory specificity-testing demonstrated that it could complete its life cycle on 2 commercially grown cultivars of Brassica rapa (choy sum and Chinese cabbage). Because of this, it is not proposed to release B. picicornis in Australia at present. Bruchela suturalis was also introduced into Australian quarantine from France but attempts to change its annual life cycle to Southern Hemisphere seasons were not successful, and a culture could not be established. Both Baris picicornis and Bruchela spp. remain promising agents, and further work on their introduction is justified by their potential for biological control of R. lutea.