MSc Thesis
Field investigations on the occurrence, incidence and damage severity of the Citrus
Leafminer Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) on Citrus crops
were conducted in Morogoro Rural, Muheza and Kinondoni districts from December
2011 to September 2012. Fifty citrus fields were randomly selected in each of Morogoro
Rural and Muheza districts from which 10 000 trees (>5 years old) were examined for
leafminer damage signs. A total of 25 seedling nurseries (plants <5 years) were assessed
in Kinondoni district. Occurrence of the pest was noted in almost all fields albeit at low
incidence (2%). Kruskal Wallis analysis of the incidence data showed neither spatial nor
temporal variations between the locations and time of survey. Damage severity in
Kinondoni showed an increasing trend from December 2011 to June 2012. Based on the
observable morphological features of the collected specimen and damage signs, the pest
was suggested to belong to the genus Phyllocnistis and the species citrella. Total
development time was longer at 20 0 C and shorter at 30 0 C with 28 days and 10 days
respectively. Oviposition period decreased with increase in temperature, from 9.26 days
at 20 0 C to 6.21 days at 30 0 C. Female insects lived longer than males across all tested
temperatures.
Royal Museum for Central Africa (RMCA), Belgium