CHROMATOMYIA FUSCULA (ZETT) (DIPT, AGROMYZIDAE) HOST-PLANT, FEEDING AND OVIPOSITION SITE PREFERENCES

In southern Norway, the grass Festuca pratensis supported the emerging overwintered population of the agromyzid Chromatormyia fuscula until the appearance of the primary host plant, spring barley (Hordeum vulga r e). Oats (Avena sativa), rye (Secale cereale) and the grass species, Dactylis glomerata and Alopecurus paratensis were alternative seconda ry hosts. C. fuscula females preferred the upper surface of the two yo ungest barley leaves for feeding and oviposition. This behaviour is ad vantageous for the farmers when applying an insecticide spray because the distribution of a contact insecticide on the upper two leaves is t he easiest possibility for plant protection practice. The earliest (Is t and 2nd) leaves of barley died quickly due to unusually warm and dry weather conditions. Consequently, larval survival on these leaves was low. Leaf numbers 3-5 supported the greatest population of successful larvae. Overwintered caged, gravid females of C. fuscula made an aver age of 3-4 punctures and laid one egg per hour.