Abstract

Allium leaf miner - Napomyza gymnostoma Loew. (Diptera, Agromyzidae) feeds on diferent species of onions (Allium spp.). Itis spreadin the wholeEurope andconsidered as oneof the most important onion pests, especially onyoung plantsinspringandautumn. During 2006 and 2007 presence of Napomyza gymnostomawas observed on onion in the Banja Luka region at seven different locations. Onion plants were visually inspected in order to find damages that are caused by adult feeding. Afterthe first damages were detected,20 plants in5 places in eachplot were randomlyselected and observed. The percentageof damaged plants was determined at every location. During springgeneration, the length of development stageswas monitored at the entomological cages in the open field. Based on the morphological characteristics, in the laboratory was confirmed the identity of the species. In 2006 the first damages caused by adult feeding were detected on 22nd April at the location Šargovac. The highest percentage of damages was found at location Vakuf 1 (50%). In 2007 the first damages of adult feeding was detected on 5th April at the location Šargovac 1, while the highest percentage of damaged plants was registered at location Vakuf 2a (41%). Larval development lasted from 29 to 34 days and pupal development 4 months, including summer diapause.