Leafminer Liriomyza trifolii population dynamics on broad bean in Upper Egypt

The leafminer Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) has become a serious pest on vegetable crops in Egypt. A study was conducted on the population dynamics of L. trifolii on broad bean in the Minia Region of Egypt from 2008 to 2010. Population densities were monitored at 50 cm and 100 cm above the field, in the 4 cardinal directions (east, west, north and south), on early and late planted host plants, and from the top, middle and bottom of the foliage. In addition, the fresh weight of infested versus non-infested leaves were compared during growth of the crop. Significantly more leafminers were trapped at 50 cm compared to 100 cm, and in traps oriented toward the north and south in two consecutive seasons. The number of leafminer mines and larvae were significantly higher on late compared to early cultivation over consecutive seasons. Leafminer mines and larval densities were relatively low on the top foliage, but were greater and similar on the middle and bottom foliage. The highest reduction percentage occurred in infested compared to non-infested leaflets, and was observed 100 days after planting. The study shows a clear relation between trap height and directions, planting date, leaflet position and plant age, and significant loss of leaf weight as leafminer infestations accumulate over the broad bean cropping season. These results will help establish better trap placement and leaf sample selection for monitoring leafminer populations and implementing integrated pest management.