Spatial Distribution and Damage Severity of Citrus Leafminer (Phyllocnistis spp. Stainton) in Major Citrus Producing Regions of Tanzania

Abstract

Field survey was conducted to determine the occurrence and damage severity of the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracilariidae) in major citrus producing regions of Tanzania between December 2011 and September 2012. In total, 14,725 citrus trees and seedlings were assessed to determine the presence or absence of P. citrella as well as its associated damage severity. A total of 10,000 citrus trees (>5 years) were sampled from Morogoro Rural and Muheza Districts, while 4,725 nursery seedlings (<5 years) from Kinondoni District. The damage severity was assessed as described by Horsfall-Barratt scale. Results revealed that leafminers were recorded in nearly all surveyed areas. Kruskal Wallis analysis suggested minimal spatial distribution of the pest incidence among the surveyed locations. Kinondoni district recorded the highest (34.11%) leafminer incidence while Muheza district had the lowest (3.74). However, the damage severity indicated an increasing trend from December 2011 through June 2012 in nursery seedlings at Kinondoni. Weather variables (especially temperature) played an important role to the pest’s development and perpetuation. Further studies need to be conducted to have a wider knowledge of the pest in all the citrus growing regions in the country.