Tree dieback in Punjab, Pakistan

Survey of 10 districts of Punjab viz. Sialkot, Gujranwala, Lahore, Faisalabad, Sheikhupura, Gujrat, Jehlem, Rawalpindi, Sargodha, and Hafizabad were undertaken from March 2003 to March 2004 to study the present status of tree dieback incidence in these areas. A total of 21 tree species were found victim of the dieback disease. The disease incidence, however, varied in different tree species. Furthermore, there was also difference in disease severity in different surveyed districts of the province. Dalbergia sissoo Roxb. and Acacia nilotica (Lam) Willd. ex Delile., were found to be the most affected species in all the districts. Among the commonly grown trees Mangifera indica L., Eucalyptus citriodora Hook., E. camal-dulensis Dehnh., Populus hybrida M. Bieb., Ficus religiosa L., F. bengalensis L., Bombax ceiba L., Syzygium cumini (L.) Skeels., Psidum guajava L., and Albizia lebbeck Benth. were found affected with dieback. The less commonly cultivated species like Toona ciliata (Roxb.) M. Roemer, Heterophragma adenophyllum Seem. ex Benth. & Hook., Ficus glomerata Roxb., Mimosup elengi, Terminalia arjuna Wight & Arn., Grevillea robusta Cunn., Ehretia acuminata R. Br., Platanus orientalis L. and Barringtonia acutangula (L.) Gaertn. were also found victims of the dieback. Termites and fungi were found to be the most common biotic factors responsible for the disease. Among the abiotic factors generally drought and environmental pollution seemed to be the main causes for dieback initiation and severity.