Investigations on the natural enemies of some Canadian weeds.
In a survey of stands of Carduus nutans, the Curculionid Ceuthorrhynchidius horridus was found in 11 out of 43 localities, mostly in the Alsace and German Rhine Valley. Of 7 other insect species regularly observed on rosettes of C. nutans, the Syrphid Chilosia sp. caused sufficient damage to warrant further investigation. In a search for the root-feeding larvae of the Tortricid Argyroploce purpurana on Sonchus arvensis, only one infestation was found (in Lower Austria). In a study of the phytophagous insects associated with Artemisia absinthium, the Cerambycid Phytoecia julii was found in the 2nd consecutive year. Out of 6 other species, Euzophera cinerosella and Eucosma pupillana were examined for host specificity. In another study, a population of Cynoglossum officinale plants in the German Rhine Valley was found to be infested with larvae of the Curculionid Ceuthorrynchus crucifer; this association was considered to merit further study. A survey and collection of Silene, Lychnis and Melandrium spp. together with the phytophagous insects associated with them was made in eastern Austria.