Population densities, spatial pattern and development of the pea leafminer(Diptera : Agromyzidae) on cucumber, swisschard and bean

Liriomyza huidobrensis, the pea leafminer, is a recently identified pest on vegetables in Lebanon. The objectives of this study were to survey the lea fminer infestation, to study its dispersion and its development on cucumber , swisschard and bean. In general, the infestation level was found to be hi gher in the middle coastal sites than in the other sites during the period of the study 1994-95. In the former sites, the pest was found to thrive on swisschard in October and November, in presence of cucumber under greenhous es, while it was encountered in significantly higher numbers on cucumber du ring the spring season, in absence of swisschard. Pairwise comparisons of T aylor's and Iwao's regression slope for L. huidobrensis larval mines indica ted a contagious dispersion on leaves of cucumber and bean, while the patte rn was random to slightly aggregated on swisschard. There was a significant ly higher number of larval mines on the lower plant stratum compared to the middle and upper strata of cucumber through the cropping season. There was a significant difference in the overall development duration (19.6-22.3 da ys) of the insect among the three hosts. The larval development duration wa s significantly shorter on bean compared to swisschard and cucumber consecu tively. However, there was no significant difference in egg or pupa duratio n among the three hosts. Results of this study provide bases for appropriat e management of the pest, taking into consideration its infestation level, spatial pattern, and development duration on the mentioned hosts.